KE Jetronic Diagnosis
05-19-2011, 06:47 PM
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Thread Starter
KE Jetronic Diagnosis
*KE Jetronic Diagnosis
Hello all on this forum. I hope to bring to some the benefits of my experience in effecting a remedy to a faulty KE Jetronic system, on a W124 Mercedes 300CE, Australian version. Not that the latter factor makes much difference, seemingly apart from the Aussie version not including a cold air input temperature sensor. It took me a long time to get there and I hope that the following information will be found of help to people with injection system problems.
It can be very daunting coming to terms with a faulty system. You have a great car but it runs disgustingly, if at all. And the solutions are costly and it seems that nobody in the world apart from a few competent service providers knows anything about it. But not only that, it seems that you need special diagnostic tools that cost the earth. When you look through the internet you find dozens of people who have paid large sums to have their systems serviced to no effect.
But here are solutions to several frequent problems that don't involve diagnostic tools much beyond a multimeter.
Before starting anything, please refer to a tutorial about how the system functions, Bosch have an excellent summary readily searched out on the internet. Search for “Bosch KE Jetronic system function” or similar.
It's likely that your symptoms include “won't start when cold or hot; backfiring; cough and splutter on acceleration”.
You will have found from your searching that a most important component is the “Over Voltage Protection Relay” and it is most important!
But there are some tricky things to check out first, before getting into the complicated parts.
First. Note that all the sensors have a return path to ground. Some have the benefit of a wire from the sensor, while others rely on current paths via the engine block and chassis. This latter path can be fraught! The engine block is of course mounted on compound engine mounts which are not electrically conductive. So there is a flexible copper conductor run from the block to the body. On my car this is located between the manifold and a mounting bracket for the ignition coil. It's flexible because there is relative motion between the engine and the body every time the engine speed changes. And because it's not ideally flexible, some reaction occurs on the attachment points at each end and they can become lose. Result? Poor hot or cold starting; coughing and spluttering.... you get the idea. To find these connections you need to take off the air cleaner, find the connecting cable and look. Check each end for tightness, broken cables etc. If they are loose, complete the job by removing the attachment, thoroughly clean the terminals and tighten them up. Then see how your vehicle behaves. In a few cases a miraculous transformation will have occurred. But the probability is not high, especially if the vehicle has a few km or miles on its clock – the electronics do not have an indefinite life!
Now precisely the same effect would occur if at the other end of the chain of supply was affected – that is the battery supply. This goes to the injection control unit, or computer if you like. This is located behind a lovely plastic moulding immediately in front of the battery. Carefully remove it by inserting a finger in between the bodywork and the moulding and you'll work it out from there. Now great care must be used in following the next check. You'll note that there is a large cable entering a plug that in turn is mounted on top of the computer and it's about 150 mm long. To remove the plug it is necessary to deflect the two horns immediately beneath the cable entering the plug towards the computer body. This will release the plug and allow it to be withdrawn. Very carefully lift the plug from its cable end, precisely in line with its attached position. The end of the plug furthest from the cable has a rectangular tongue located in a slot in the computer's body and this is the last part to come free. Of course it is the first part to position when replacing the plug. And it's here that we must observe absolute care. You'll see that the computer has 25 flat pins that each have to enter a connector slot in the plug and these connector slots are fragile. The first connector is say 25 mm from the tongue and as I said above, the plug is about 150 mm long. So in replacing the plug there is a mechanical advantage of about 6 at the point where the first connector pin enters its fragile socket. On my car the first slot had been damaged due to the plug not having been first positioned so the tongue fully engaged its slot and then possibly the plug was pressed into place in such a way that it was not completely parallel with the socket. It took a fair bit of care to realign the connector so that a good contact was effected, using a tiny jewellers screwdriver, but it was done. It did make a difference.
But those things are almost outside the realm of the KE Jetronic system itself and I'll go on to that now.
Fuel Pressures
When the key is turned on, the fuel pump operates for one second, bringing fuel in the system up to operating levels. Upon engine start, the fuel pump is turned on again. Serious running problems can be experienced if fuel pressures are too low. If you are fortunate enough to have access to fuel pressure measuring devices, it's great to prove the pressures right, this can save a lot of time.
If your vehicle will not start at all, a faulty fuel pump or electrical supply can be suspected. It's not much use turning on the key and then crawling under the rear of the vehicle to check whether the pump is operating, because after the first one second, it should have turned off anyway. That is a two person operation, one turning on the key, one listening for pump operation - for one second only!
There's a fuel filter in the line, if it is blocked you'll have poor fuel supply and erratic running, so it will need to be changed. There's another component in the fuel line called the Accumulator. This is just a spring loaded reservoir that maintains fuel pressure during times of low fuel volume requirements, when the pump may be turned off, in the same way as at starting. A symptom of a faulty Accumulator is stalling when idling, say at traffic lights. The acid test for this is to take off the air cleaner to expose the air flow sensor plate. Start the vehicle and run it just for a short time, then shut it down. After about one minute, depress the air flow sensor plate. It should offer resistance to your effort, indicating that residual fuel pressure is being held. If the plate moves downward without resistance, you need a new accumulator.
Diagnosis by Codes
The system is provided with a diagnostic socket from which electrical readings are made that show the condition of the various components. On my car there is an 8 pin socket, concealed by a screw cap, located just above the ignition coil on the inner mudguard. Readings for the injection system are taken from pins 2 and 3 of the socket. Other cars have other styles and sizes of sockets, but there seems to be some commonality in that pins 2 and 3 are used for this purpose. You'll need to determine this from on-line searches, specifically for your model.
But before these codes can be read reliably, the condition of the Over Voltage Protection (OVP) Relay needs to be checked. This relay performs the valuable task of making sure that any short term voltage spikes do not burn out sensitive electronic parts throughout the vehicle, particularly in the computers. Reports abound of OVP relays with failed soldered joint on their printed circuit boards and if these are dodgy, the supply voltage to the injection system components can be intermittently interrupted, producing the same symptoms as the faulty ground or battery connections mentioned above. The OVP relay, while protecting the electronics, turns on the fuel pump relay and other components that prepare the injection system for operation. So a faulty supply from this relay can give symptoms of horrible running, while masking other faults that may be present. You might be able to roughly gauge whether the OVP relay is OK by measuring the voltage at the fuel pump relay while giving the OVP relay a bump. A voltage loss is a sure indication of a problem OVP, but such a method is not reliable. If you don't want to start out with a new or known to be good used unit, you can follow the diagnostic steps, but if you receive variable results, change it out.
These electrical readings are codes, each of which indicates something. There are two forms of these codes. They consist of a set of pulses output by the computer, rising in voltage from zero to the injection system voltage (this can be just a bit less that battery voltage, , depending upon engine operating speed) and the number pulses indicates the nature of the fault. If you don't have access to the proper gizmo to measure these pulses, you can make a pulse counter from a light emitting diode with appropriate resistor and a three connecting leads. Making the test leads is covered in many places on the internet, as is using them to get the computer to output the diagnostic codes. Once connected, you instruct the computer to output one code at a time, then count the number of pulses, then look up a table from Mr Benz to identify the faulty part. My vehicle is a 1988 model and I was not able to find the list, but I reckon that almost everybody else's models are covered by information on many sites. There's some good news though. Alternative checks can be made just using a multimeter on pins 2 and 3 of the diagnostic socket. In one form of multimeter test, the average value of the pulse train voltage is measured and in another form, the on/off ratio of the pulse train is measured. In the following, the average voltage method is described.
Test 1
Average voltage method. Turn on the key, but don't start the engine. Measure the DC voltage between pins 2 and 3. This should be 30% of the injection system voltage as measured usually at pin 6 of the diagnostic socket – it's a little less than battery voltage under the conditions of the test, ie whether the engine is running or not) and correspond to Mercedes' specification of a 70% duty cycle or “on/off ratio”. In fact Mercedes uses the total proportion of its off period as its indicator number, but the multimeter respond to the proportion of time the pulses are on, at injection system voltage. Hence the 30% mention above – 100% minus 70% equals 30%. This initial reading doesn't tell you much, only that the computer is capable of putting out diagnostic codes – but that's something! If you don't receive any readings, maybe your computer is past its prime.
Test 2
Same test conditions
Deflect the air flow sensor plate. The duty cycle should decrease to 10%, that is, the multimeter should read about 11 volts. If no change occurs, that is the reading still is about 3 volts, test the throttle valve switch (Job 07.3-121 in Mercedes shop manuals). Please note that the 10% is nominal, 9% to 11% is seemingly OK.
Test 3
Same test conditions
Deflect the throttle fully, the duty cycle should read 20% or about 10 volts, indicating that the Full Load Contact switch is OK, unless it decreases to only 40% or about 7 volts. In this case test the air flow sensor potentiometer (Job 07.3-121 in the Mercedes shop manual). Again 20% or close to it is OK.
Test 4
Engine operating at 80 degrees C. Check the Lambda Ratio. The Lambda Ratio is the ideal ratio of air/fuel that enables complete combustion of the fuel. It is 14.7/1. The controlling element is the Oxygen sensor in the exhaust gas stream. This sensor operates only at high temperature, so is provided with a heater supplied by the battery, via the fuel pump relay. In operation, it determines the proportion of oxygen present in the exhaust gas and signals the computer to provide more or less fuel to maintain an average value corresponding to the ideal Lambda ratio.
Measure the voltage between pins 2 and 3. It should fluctuate, showing that the oxygen sensor is causing the computer to adjust the mixture on a continuous basis. The duty cycle readings should be between 45% and 55 % . Higher than this indicates a lean mixture and lower indicates rich. The voltage levels corresponding to these values are, depending on the battery voltage while running are 7.4 to 6.1. (These values assume a system voltage of 13.5.)
If there is no fluctuation at all, just a steady reading, something is wrong with the oxygen sensor or its supply. It is located not far along the exhaust pipe and replacing it involves a big spanner and a lot of effort. Its wiring is located under the floor mats on the side of the vehicle above the exhaust system.
My vehicle presented readings indicating 55% to 65%, so running was lean. The symptoms were sluggish pickup, coughing and sputtering as well as stalling. The remedy involved adjusting the mixture screw in the injection distributor, but we'll discuss this later.
Air Flow Sensor Potentiometer
This is one of the very important pieces of the system. It is operated by the air flow sensor, the circular metal plate that deflects under the influence of the air flowing into the engine, which in turn is determined by the throttle opening. It is a fair bit more complex than a volume control on your stereo, but it does the same thing. As the air flow sensor is deflected by the air stream, the shaft upon which it rotates moves sliding contacts over a track of resistive material and this feeds the computer with a voltage reading which allows it to control the precise amount of fuel required by the measured air flow. Now every time the throttle is operated, the air flow sensor deflects and moves the sliding contacts across the resistance material and that can happen a few million times, I guess, in the lifetime of a car. So the track wears and the computer can then be fed with a certain voltage at one throttle opening and with just a very small movement the sliding contacts encounter an area where no resistance material remains, so the voltage indicating air flow drops to zero. The computer doesn't know what to do, so erratic operation is the result.
Testing this component is carried out with ignition on and engine off. The potentiometer is connected by a three pin plug, with locking tags at top and bottom. Ease these out and slightly withdraw the plug, so that the socket pins can be accessed by test leads from your multimeter. The top and bottom pins should have nominally 5 volts across them, as supplied by the computer. The centre pin feeds back to the computer a voltage less than 5 volts for each position of the air flow meter. Connect the multimeter between the centre and the top pin and watch the voltage reading as you very gradually deflect the air flow meter plate. The voltage should increase continually, never dropping out to zero. If it does, you need a new potentiometer. Mercedes only sells these already mounted on a replacement air flow meter and you may think that its cost is comparable to the value of your vehicle. There is information on the web about obtaining a replacement potentiometer at a much lower cost. If you go this way, you'll have to remove the old pot and replace it with a new one, then calibrate it, but that's a simple matter really. One reason for which Mercedes provides an all new solution may be that the sliders that run over the resistance tracks remain in the housing and they may also be worn, so installing a new pot may not produce any improvement. Removing the old potentiometer involves using a very fine screwdriver to insert in the gap between the two roughly circular plastic covers on the front at either end of the potentiometer housing and easing them out, exposing four Torx screws that mount the potentiometer to the air flow sensor body. At this stage it's a really good idea to put a pencil mark around the pot on the air flow sensor body, as an aid in getting the replacement one roughly in the right position. Undo the screws and gently withdraw the pot from its shaft. Look at the tracks and marvel at how the car operated at all! You'll note that the four mounting screws go through slotted holes in the pot housing that allow it to be rotated relative to its operating shaft and this is how the pot is calibrated. Once you have replaced the pot with the screws just loose enough to allow its rotation around the shaft, you reconnect the three pin plug, again with the socket pins exposed for measurement, then measure the voltage at the centre pin. Turn the new pot around the operating shaft until you read about 1 volt. At the 1 volt level the engine will be running rich, but if you try a lower initial setting, you may not be able to start the engine. Now start the engine and get it up to operating temperature, then adjust the pot position until you read 0.7 volts between ground and the centre pin. The pot is now calibrated.
If that was the main problem, your vehicle should now be much improved.
Mixture Adjustment
There's a lot of instruction on the web cautioning any playing around with the mixture control. The screw that allows adjustment is protected by various types of guards against ready access, so Mercedes takes it seriously. But it isn't too much of a problem, the biggest part of the task is removing the guards. Consult the web for details of your particular model. The adjustment consists of using a 3 mm Allen key in a spring loaded coupling to turn an adjustment right inside the injector housing. The screw raises or lowers a plate that changes the aperture through which fuel is dispensed to the injectors. It is essential that you don't leave the Allen key in place after the adjustment is made, because it can cause serious damage to the injector system next time you start.
That having been said, here's how. Bring the engine up to normal operating temperature, about 80 degrees C. Then connect the multimeter to terminals 2 and 3 and adjust the screw until the voltage readings fluctuate between 6 and 7.4. Make adjustments almost microscopically, the tiniest turn will have a significant effect. Allow at least 10 seconds between adjustment and reading, to allow the system to settle into its new operating condition. Those voltage readings correspond to a Lambda ratio of between 45% and 55%, just what you want.
The Cold Start Valve
There is a cold start valve, in the form of another injector that supplies additional fuel when starting from cold. If it or its wiring are faulty, cold starting can be awful. The injector is turned on by a solenoid operated valve that receives its supply from the computer. To check the electrical operation, unclip the stainless steel retainer on the electrical connector and withdraw it. Measure the coil for continuity, you should read about 10 ohms. If that's OK, you need to know if you are receiving an adequate supply to the terminals. The most reliable way of doing that is to measure the current flow through the solenoid, so you have to jury rig a pair of test leads and set your multimeter to read DC amps. Expect 1.2 amps. If all that seems OK but the symptoms persist, you'll need to remove the cold start valve and watch it when simulating a cold start. Put the valve in a jar while connected to its cable and turn on the ignition. If you are not rewarded by a nice spray into the jar, the valve is shot. If you are so rewarded, you'll know why it is necessary to put the valve in a jar. A big one preferably.
Another problem that can arise with these valves is continuous operation, so that the vehicle runs rich, fuel costs rise, spark plugs are sooty and the engine oil is being washed off the bores! Get a new one.
The Coolant Temperature Sensor
The function of the coolant temperature sensor is to tell the controller the current engine temperature. When the engine is cold, the resistance of the sensor is around 2,500 ohms and an appropriate signal is given to the controller to cause mixture enrichment for starting. As the engine warms up to operating temperature, the resistance of this sensor falls to about 350 ohms, telling the controller that no enrichment is necessary. Between cold and hot engine temperatures, the degree of enrichment is progressively reduced.
This component seems fairly forgiving. The main problem for my engine was difficult hot starting. But my coolant temperature sensor was non-functional, so I temporarily wired in a 350 ohm resistor, thus providing advice to the controller that the engine was permanently hot. I had no trouble starting the engine when it was cold in warmer weather, but when ambient temperatures fell to below 15 degrees C, cold starting became a little troublesome. Maybe it would stall immediately upon starting and sometimes it took me three attempts before all was well. But if it does not meet specifications fit a new one.
The Electro-Hydraulic Actuator (EHA)
This is an important (and expensive!) part of the system. It is attached to the rear of the fuel distributor and has the function of opening and closing the fuel metering valves inside the distributor in accordance with the demands of the engine and the instructions from the computer. It is basically an electromagnet and the degree of opening and closing of the fuel metering valves is determined by the strength of the electro-magnetic force it develops, in turn determined by the current flow through its coil.
Consultation of the specifications for current flows through the coil shows that for various models, quite different currents are needed. But commonly, the maximum current flow is 15 milliamps in response to a throttle blip, while at idling, a steady current of about 1 milliamp is normal. It is stressed here that the currents are completely dependent upon which model your are working with, so look carefully at the specifications.
The coil has a resistance of about 20 ohms and you can check this by removing the connector and applying your multimeter. In order to persuade a current of 15 milliamps to flow in the coil, the applied voltage has to be about 0.3 volts. Now if you use a digital type multimeter to measure the voltage output from the computer with the EHA disconnected you may read as much as 4 volts. Ignore that. It's the result of using a very sensitive instrument while the computer is not in its normal operating state. When it is in that state, it will be putting out voltages only up to a maximum of 0.3 volts. What I'm getting at here is that the only valid readings to take relevant to the EHA are those of current. So you need to make up a set of test leads that will let you connect your multimeter in the EHA circuit. Then measure the current flows. No flow at all means that you have an open circuit coil, wiring or connector.
Final Remarks
All the best with your fault finding!
Megawatt Man
Hello all on this forum. I hope to bring to some the benefits of my experience in effecting a remedy to a faulty KE Jetronic system, on a W124 Mercedes 300CE, Australian version. Not that the latter factor makes much difference, seemingly apart from the Aussie version not including a cold air input temperature sensor. It took me a long time to get there and I hope that the following information will be found of help to people with injection system problems.
It can be very daunting coming to terms with a faulty system. You have a great car but it runs disgustingly, if at all. And the solutions are costly and it seems that nobody in the world apart from a few competent service providers knows anything about it. But not only that, it seems that you need special diagnostic tools that cost the earth. When you look through the internet you find dozens of people who have paid large sums to have their systems serviced to no effect.
But here are solutions to several frequent problems that don't involve diagnostic tools much beyond a multimeter.
Before starting anything, please refer to a tutorial about how the system functions, Bosch have an excellent summary readily searched out on the internet. Search for “Bosch KE Jetronic system function” or similar.
It's likely that your symptoms include “won't start when cold or hot; backfiring; cough and splutter on acceleration”.
You will have found from your searching that a most important component is the “Over Voltage Protection Relay” and it is most important!
But there are some tricky things to check out first, before getting into the complicated parts.
First. Note that all the sensors have a return path to ground. Some have the benefit of a wire from the sensor, while others rely on current paths via the engine block and chassis. This latter path can be fraught! The engine block is of course mounted on compound engine mounts which are not electrically conductive. So there is a flexible copper conductor run from the block to the body. On my car this is located between the manifold and a mounting bracket for the ignition coil. It's flexible because there is relative motion between the engine and the body every time the engine speed changes. And because it's not ideally flexible, some reaction occurs on the attachment points at each end and they can become lose. Result? Poor hot or cold starting; coughing and spluttering.... you get the idea. To find these connections you need to take off the air cleaner, find the connecting cable and look. Check each end for tightness, broken cables etc. If they are loose, complete the job by removing the attachment, thoroughly clean the terminals and tighten them up. Then see how your vehicle behaves. In a few cases a miraculous transformation will have occurred. But the probability is not high, especially if the vehicle has a few km or miles on its clock – the electronics do not have an indefinite life!
Now precisely the same effect would occur if at the other end of the chain of supply was affected – that is the battery supply. This goes to the injection control unit, or computer if you like. This is located behind a lovely plastic moulding immediately in front of the battery. Carefully remove it by inserting a finger in between the bodywork and the moulding and you'll work it out from there. Now great care must be used in following the next check. You'll note that there is a large cable entering a plug that in turn is mounted on top of the computer and it's about 150 mm long. To remove the plug it is necessary to deflect the two horns immediately beneath the cable entering the plug towards the computer body. This will release the plug and allow it to be withdrawn. Very carefully lift the plug from its cable end, precisely in line with its attached position. The end of the plug furthest from the cable has a rectangular tongue located in a slot in the computer's body and this is the last part to come free. Of course it is the first part to position when replacing the plug. And it's here that we must observe absolute care. You'll see that the computer has 25 flat pins that each have to enter a connector slot in the plug and these connector slots are fragile. The first connector is say 25 mm from the tongue and as I said above, the plug is about 150 mm long. So in replacing the plug there is a mechanical advantage of about 6 at the point where the first connector pin enters its fragile socket. On my car the first slot had been damaged due to the plug not having been first positioned so the tongue fully engaged its slot and then possibly the plug was pressed into place in such a way that it was not completely parallel with the socket. It took a fair bit of care to realign the connector so that a good contact was effected, using a tiny jewellers screwdriver, but it was done. It did make a difference.
But those things are almost outside the realm of the KE Jetronic system itself and I'll go on to that now.
Fuel Pressures
When the key is turned on, the fuel pump operates for one second, bringing fuel in the system up to operating levels. Upon engine start, the fuel pump is turned on again. Serious running problems can be experienced if fuel pressures are too low. If you are fortunate enough to have access to fuel pressure measuring devices, it's great to prove the pressures right, this can save a lot of time.
If your vehicle will not start at all, a faulty fuel pump or electrical supply can be suspected. It's not much use turning on the key and then crawling under the rear of the vehicle to check whether the pump is operating, because after the first one second, it should have turned off anyway. That is a two person operation, one turning on the key, one listening for pump operation - for one second only!
There's a fuel filter in the line, if it is blocked you'll have poor fuel supply and erratic running, so it will need to be changed. There's another component in the fuel line called the Accumulator. This is just a spring loaded reservoir that maintains fuel pressure during times of low fuel volume requirements, when the pump may be turned off, in the same way as at starting. A symptom of a faulty Accumulator is stalling when idling, say at traffic lights. The acid test for this is to take off the air cleaner to expose the air flow sensor plate. Start the vehicle and run it just for a short time, then shut it down. After about one minute, depress the air flow sensor plate. It should offer resistance to your effort, indicating that residual fuel pressure is being held. If the plate moves downward without resistance, you need a new accumulator.
Diagnosis by Codes
The system is provided with a diagnostic socket from which electrical readings are made that show the condition of the various components. On my car there is an 8 pin socket, concealed by a screw cap, located just above the ignition coil on the inner mudguard. Readings for the injection system are taken from pins 2 and 3 of the socket. Other cars have other styles and sizes of sockets, but there seems to be some commonality in that pins 2 and 3 are used for this purpose. You'll need to determine this from on-line searches, specifically for your model.
But before these codes can be read reliably, the condition of the Over Voltage Protection (OVP) Relay needs to be checked. This relay performs the valuable task of making sure that any short term voltage spikes do not burn out sensitive electronic parts throughout the vehicle, particularly in the computers. Reports abound of OVP relays with failed soldered joint on their printed circuit boards and if these are dodgy, the supply voltage to the injection system components can be intermittently interrupted, producing the same symptoms as the faulty ground or battery connections mentioned above. The OVP relay, while protecting the electronics, turns on the fuel pump relay and other components that prepare the injection system for operation. So a faulty supply from this relay can give symptoms of horrible running, while masking other faults that may be present. You might be able to roughly gauge whether the OVP relay is OK by measuring the voltage at the fuel pump relay while giving the OVP relay a bump. A voltage loss is a sure indication of a problem OVP, but such a method is not reliable. If you don't want to start out with a new or known to be good used unit, you can follow the diagnostic steps, but if you receive variable results, change it out.
These electrical readings are codes, each of which indicates something. There are two forms of these codes. They consist of a set of pulses output by the computer, rising in voltage from zero to the injection system voltage (this can be just a bit less that battery voltage, , depending upon engine operating speed) and the number pulses indicates the nature of the fault. If you don't have access to the proper gizmo to measure these pulses, you can make a pulse counter from a light emitting diode with appropriate resistor and a three connecting leads. Making the test leads is covered in many places on the internet, as is using them to get the computer to output the diagnostic codes. Once connected, you instruct the computer to output one code at a time, then count the number of pulses, then look up a table from Mr Benz to identify the faulty part. My vehicle is a 1988 model and I was not able to find the list, but I reckon that almost everybody else's models are covered by information on many sites. There's some good news though. Alternative checks can be made just using a multimeter on pins 2 and 3 of the diagnostic socket. In one form of multimeter test, the average value of the pulse train voltage is measured and in another form, the on/off ratio of the pulse train is measured. In the following, the average voltage method is described.
Test 1
Average voltage method. Turn on the key, but don't start the engine. Measure the DC voltage between pins 2 and 3. This should be 30% of the injection system voltage as measured usually at pin 6 of the diagnostic socket – it's a little less than battery voltage under the conditions of the test, ie whether the engine is running or not) and correspond to Mercedes' specification of a 70% duty cycle or “on/off ratio”. In fact Mercedes uses the total proportion of its off period as its indicator number, but the multimeter respond to the proportion of time the pulses are on, at injection system voltage. Hence the 30% mention above – 100% minus 70% equals 30%. This initial reading doesn't tell you much, only that the computer is capable of putting out diagnostic codes – but that's something! If you don't receive any readings, maybe your computer is past its prime.
Test 2
Same test conditions
Deflect the air flow sensor plate. The duty cycle should decrease to 10%, that is, the multimeter should read about 11 volts. If no change occurs, that is the reading still is about 3 volts, test the throttle valve switch (Job 07.3-121 in Mercedes shop manuals). Please note that the 10% is nominal, 9% to 11% is seemingly OK.
Test 3
Same test conditions
Deflect the throttle fully, the duty cycle should read 20% or about 10 volts, indicating that the Full Load Contact switch is OK, unless it decreases to only 40% or about 7 volts. In this case test the air flow sensor potentiometer (Job 07.3-121 in the Mercedes shop manual). Again 20% or close to it is OK.
Test 4
Engine operating at 80 degrees C. Check the Lambda Ratio. The Lambda Ratio is the ideal ratio of air/fuel that enables complete combustion of the fuel. It is 14.7/1. The controlling element is the Oxygen sensor in the exhaust gas stream. This sensor operates only at high temperature, so is provided with a heater supplied by the battery, via the fuel pump relay. In operation, it determines the proportion of oxygen present in the exhaust gas and signals the computer to provide more or less fuel to maintain an average value corresponding to the ideal Lambda ratio.
Measure the voltage between pins 2 and 3. It should fluctuate, showing that the oxygen sensor is causing the computer to adjust the mixture on a continuous basis. The duty cycle readings should be between 45% and 55 % . Higher than this indicates a lean mixture and lower indicates rich. The voltage levels corresponding to these values are, depending on the battery voltage while running are 7.4 to 6.1. (These values assume a system voltage of 13.5.)
If there is no fluctuation at all, just a steady reading, something is wrong with the oxygen sensor or its supply. It is located not far along the exhaust pipe and replacing it involves a big spanner and a lot of effort. Its wiring is located under the floor mats on the side of the vehicle above the exhaust system.
My vehicle presented readings indicating 55% to 65%, so running was lean. The symptoms were sluggish pickup, coughing and sputtering as well as stalling. The remedy involved adjusting the mixture screw in the injection distributor, but we'll discuss this later.
Air Flow Sensor Potentiometer
This is one of the very important pieces of the system. It is operated by the air flow sensor, the circular metal plate that deflects under the influence of the air flowing into the engine, which in turn is determined by the throttle opening. It is a fair bit more complex than a volume control on your stereo, but it does the same thing. As the air flow sensor is deflected by the air stream, the shaft upon which it rotates moves sliding contacts over a track of resistive material and this feeds the computer with a voltage reading which allows it to control the precise amount of fuel required by the measured air flow. Now every time the throttle is operated, the air flow sensor deflects and moves the sliding contacts across the resistance material and that can happen a few million times, I guess, in the lifetime of a car. So the track wears and the computer can then be fed with a certain voltage at one throttle opening and with just a very small movement the sliding contacts encounter an area where no resistance material remains, so the voltage indicating air flow drops to zero. The computer doesn't know what to do, so erratic operation is the result.
Testing this component is carried out with ignition on and engine off. The potentiometer is connected by a three pin plug, with locking tags at top and bottom. Ease these out and slightly withdraw the plug, so that the socket pins can be accessed by test leads from your multimeter. The top and bottom pins should have nominally 5 volts across them, as supplied by the computer. The centre pin feeds back to the computer a voltage less than 5 volts for each position of the air flow meter. Connect the multimeter between the centre and the top pin and watch the voltage reading as you very gradually deflect the air flow meter plate. The voltage should increase continually, never dropping out to zero. If it does, you need a new potentiometer. Mercedes only sells these already mounted on a replacement air flow meter and you may think that its cost is comparable to the value of your vehicle. There is information on the web about obtaining a replacement potentiometer at a much lower cost. If you go this way, you'll have to remove the old pot and replace it with a new one, then calibrate it, but that's a simple matter really. One reason for which Mercedes provides an all new solution may be that the sliders that run over the resistance tracks remain in the housing and they may also be worn, so installing a new pot may not produce any improvement. Removing the old potentiometer involves using a very fine screwdriver to insert in the gap between the two roughly circular plastic covers on the front at either end of the potentiometer housing and easing them out, exposing four Torx screws that mount the potentiometer to the air flow sensor body. At this stage it's a really good idea to put a pencil mark around the pot on the air flow sensor body, as an aid in getting the replacement one roughly in the right position. Undo the screws and gently withdraw the pot from its shaft. Look at the tracks and marvel at how the car operated at all! You'll note that the four mounting screws go through slotted holes in the pot housing that allow it to be rotated relative to its operating shaft and this is how the pot is calibrated. Once you have replaced the pot with the screws just loose enough to allow its rotation around the shaft, you reconnect the three pin plug, again with the socket pins exposed for measurement, then measure the voltage at the centre pin. Turn the new pot around the operating shaft until you read about 1 volt. At the 1 volt level the engine will be running rich, but if you try a lower initial setting, you may not be able to start the engine. Now start the engine and get it up to operating temperature, then adjust the pot position until you read 0.7 volts between ground and the centre pin. The pot is now calibrated.
If that was the main problem, your vehicle should now be much improved.
Mixture Adjustment
There's a lot of instruction on the web cautioning any playing around with the mixture control. The screw that allows adjustment is protected by various types of guards against ready access, so Mercedes takes it seriously. But it isn't too much of a problem, the biggest part of the task is removing the guards. Consult the web for details of your particular model. The adjustment consists of using a 3 mm Allen key in a spring loaded coupling to turn an adjustment right inside the injector housing. The screw raises or lowers a plate that changes the aperture through which fuel is dispensed to the injectors. It is essential that you don't leave the Allen key in place after the adjustment is made, because it can cause serious damage to the injector system next time you start.
That having been said, here's how. Bring the engine up to normal operating temperature, about 80 degrees C. Then connect the multimeter to terminals 2 and 3 and adjust the screw until the voltage readings fluctuate between 6 and 7.4. Make adjustments almost microscopically, the tiniest turn will have a significant effect. Allow at least 10 seconds between adjustment and reading, to allow the system to settle into its new operating condition. Those voltage readings correspond to a Lambda ratio of between 45% and 55%, just what you want.
The Cold Start Valve
There is a cold start valve, in the form of another injector that supplies additional fuel when starting from cold. If it or its wiring are faulty, cold starting can be awful. The injector is turned on by a solenoid operated valve that receives its supply from the computer. To check the electrical operation, unclip the stainless steel retainer on the electrical connector and withdraw it. Measure the coil for continuity, you should read about 10 ohms. If that's OK, you need to know if you are receiving an adequate supply to the terminals. The most reliable way of doing that is to measure the current flow through the solenoid, so you have to jury rig a pair of test leads and set your multimeter to read DC amps. Expect 1.2 amps. If all that seems OK but the symptoms persist, you'll need to remove the cold start valve and watch it when simulating a cold start. Put the valve in a jar while connected to its cable and turn on the ignition. If you are not rewarded by a nice spray into the jar, the valve is shot. If you are so rewarded, you'll know why it is necessary to put the valve in a jar. A big one preferably.
Another problem that can arise with these valves is continuous operation, so that the vehicle runs rich, fuel costs rise, spark plugs are sooty and the engine oil is being washed off the bores! Get a new one.
The Coolant Temperature Sensor
The function of the coolant temperature sensor is to tell the controller the current engine temperature. When the engine is cold, the resistance of the sensor is around 2,500 ohms and an appropriate signal is given to the controller to cause mixture enrichment for starting. As the engine warms up to operating temperature, the resistance of this sensor falls to about 350 ohms, telling the controller that no enrichment is necessary. Between cold and hot engine temperatures, the degree of enrichment is progressively reduced.
This component seems fairly forgiving. The main problem for my engine was difficult hot starting. But my coolant temperature sensor was non-functional, so I temporarily wired in a 350 ohm resistor, thus providing advice to the controller that the engine was permanently hot. I had no trouble starting the engine when it was cold in warmer weather, but when ambient temperatures fell to below 15 degrees C, cold starting became a little troublesome. Maybe it would stall immediately upon starting and sometimes it took me three attempts before all was well. But if it does not meet specifications fit a new one.
The Electro-Hydraulic Actuator (EHA)
This is an important (and expensive!) part of the system. It is attached to the rear of the fuel distributor and has the function of opening and closing the fuel metering valves inside the distributor in accordance with the demands of the engine and the instructions from the computer. It is basically an electromagnet and the degree of opening and closing of the fuel metering valves is determined by the strength of the electro-magnetic force it develops, in turn determined by the current flow through its coil.
Consultation of the specifications for current flows through the coil shows that for various models, quite different currents are needed. But commonly, the maximum current flow is 15 milliamps in response to a throttle blip, while at idling, a steady current of about 1 milliamp is normal. It is stressed here that the currents are completely dependent upon which model your are working with, so look carefully at the specifications.
The coil has a resistance of about 20 ohms and you can check this by removing the connector and applying your multimeter. In order to persuade a current of 15 milliamps to flow in the coil, the applied voltage has to be about 0.3 volts. Now if you use a digital type multimeter to measure the voltage output from the computer with the EHA disconnected you may read as much as 4 volts. Ignore that. It's the result of using a very sensitive instrument while the computer is not in its normal operating state. When it is in that state, it will be putting out voltages only up to a maximum of 0.3 volts. What I'm getting at here is that the only valid readings to take relevant to the EHA are those of current. So you need to make up a set of test leads that will let you connect your multimeter in the EHA circuit. Then measure the current flows. No flow at all means that you have an open circuit coil, wiring or connector.
Final Remarks
All the best with your fault finding!
Megawatt Man
Last edited by amdeutsch; 11-27-2011 at 07:10 AM.
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daniel62 (08-19-2018)
07-31-2011, 10:42 PM
#2
Newbie
megawatt...
wow...a lot of information...i will keep this handy. My 92 300ce has been having hard starting issues and hesitation issues. I read on the forum about the OVP relay and decided to check the fuses on mine. Fuses were fine...HOWEVER...the relay was full to the top with water! I'm going to replace it but i believe i may still have an issue with my KE jet...hoping not thought! Gonna start with the the OVP and progress from there..
wow...a lot of information...i will keep this handy. My 92 300ce has been having hard starting issues and hesitation issues. I read on the forum about the OVP relay and decided to check the fuses on mine. Fuses were fine...HOWEVER...the relay was full to the top with water! I'm going to replace it but i believe i may still have an issue with my KE jet...hoping not thought! Gonna start with the the OVP and progress from there..
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daniel62 (08-19-2018)
08-01-2011, 07:34 AM
#3
Junior Member
Thread Starter
G'day Chaser1, Heaven only knows what electrical conditions could exist with a water-full OVP! But I'm game to intuit that they would not be good. I would guess that you are missing the lovely plastic moulding to which I refer in paragraph 10 of my posting. This would have protected the OVP, the fuel pump relay and the all important injection computer/controller from water leaking downwards via the engine cover - maybe stateside you call it the hood? or the bonnet? If that is so, try to fit a new one. A plastic bag may get you by in the meantime.PLease post your findings. Megawatt Man.
Last edited by Megawatt Man; 08-01-2011 at 07:35 AM. Reason: typo
08-01-2011, 11:53 PM
#4
Newbie
Megawatt...
Well...replaced the OVP today, solved one set of problems I was having, but there is still an underlying problem that I guess I will throw out to the forum and see if anyone has any suggestions. BTW...the OVP that was originally on the car was a KAE brand..which i'm assuming is an aftermarket replacement. The OEM one I bought today from the local Merc dealer has a sealing O-ring where the cap closes over the fuses where the KAE relay did not....no more water in the OVP relay!
Well...replaced the OVP today, solved one set of problems I was having, but there is still an underlying problem that I guess I will throw out to the forum and see if anyone has any suggestions. BTW...the OVP that was originally on the car was a KAE brand..which i'm assuming is an aftermarket replacement. The OEM one I bought today from the local Merc dealer has a sealing O-ring where the cap closes over the fuses where the KAE relay did not....no more water in the OVP relay!
08-02-2011, 07:54 AM
#6
Newbie
Here's what I put in my other post.
1: still has hard starting issues--turns over 10-15 seconds before it will finally fire up.
2: once it starts, it runs great and accelerates great until it reaches what I would call "operating temp", at which time it has a very pronounced low RPM hesitation. If you're starting from a stop and you accelerate normally, this thing won't hardly get out of it's own way, it falls flat and backfires through the intake like it's going to stall. HOWEVER, if you press the pedal to the floor just momentarily and let it back up, it will go ahead and get on down the road.
3: it has a very strong catalyst smell from the exhaust when it's idling which tends to make me think that maybe it's running too rich.
1: still has hard starting issues--turns over 10-15 seconds before it will finally fire up.
2: once it starts, it runs great and accelerates great until it reaches what I would call "operating temp", at which time it has a very pronounced low RPM hesitation. If you're starting from a stop and you accelerate normally, this thing won't hardly get out of it's own way, it falls flat and backfires through the intake like it's going to stall. HOWEVER, if you press the pedal to the floor just momentarily and let it back up, it will go ahead and get on down the road.
3: it has a very strong catalyst smell from the exhaust when it's idling which tends to make me think that maybe it's running too rich.
08-02-2011, 08:17 AM
#7
Junior Member
Thread Starter
If you don't have a multimeter, find a friend who does! Then perform test 4 in the diatribe I posted. If the oxygen sensor is OK, there will be fluctuation in the reading over a range of about 10%. The magnitude of the reading will tell you if the engine is running rich or lean. Also check out the resistance of the engine coolant sensor, look for the values posted. I think in your locality though, at this time of the year the ambient temperature will be over 15 deg C, so cold starting should be OK, as it was in my case. Also look for a loose connection on the earthing bond between engine and chassis, a high resistance will give the injection computer unpredictable signals and confuse it.
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08-02-2011, 10:34 PM
#8
Newbie
Megawatt....
I do have a multimeter....but its an old simpson analog...oldie but goodie. I will invest in a digital multimeter this weekend...I have been eyeballing the Fluke meters for some time now, so it sounds like it may be a good time to invest. I will perform the tests on the O2 sensor and the coolant sensor as well. On the subject of the ground, I do not even remember seeing one on my car, and I have spent quite a few hours under the hood...although I cant say that i was specifically looking for that though. I was mainly concentrating on the wiring harness, which to my relief, was not degraded and was pliable. I will look for the ground wire while I am working on the car this weekend. When I drive it on the freeway, it runs and rides so good...it is a really solid car, but god forbid that I have to stop and start again....that is an adventure in itself. I believe I will name the care Dr. Jeklyll and Mr. Hyde....may even get vanity plates that read jeklhyd..haha! Hope you are doing well!
I do have a multimeter....but its an old simpson analog...oldie but goodie. I will invest in a digital multimeter this weekend...I have been eyeballing the Fluke meters for some time now, so it sounds like it may be a good time to invest. I will perform the tests on the O2 sensor and the coolant sensor as well. On the subject of the ground, I do not even remember seeing one on my car, and I have spent quite a few hours under the hood...although I cant say that i was specifically looking for that though. I was mainly concentrating on the wiring harness, which to my relief, was not degraded and was pliable. I will look for the ground wire while I am working on the car this weekend. When I drive it on the freeway, it runs and rides so good...it is a really solid car, but god forbid that I have to stop and start again....that is an adventure in itself. I believe I will name the care Dr. Jeklyll and Mr. Hyde....may even get vanity plates that read jeklhyd..haha! Hope you are doing well!
08-03-2011, 12:26 AM
#9
Junior Member
Thread Starter
G'day chaser1, the analogue meter will read the voltage values you need just as well as the Fluke. You need to measure the voltage as supplied to the injection controller/computer (on my vehicle at terminal 6 in the diagnostic connector) then read the fluctuating (hopefully fluctuating!) voltage then check that the reading you observe expressed as a percentage coincides near enough to the required values. For example, if the supply voltage reads 13.2 V, a voltage reading of 50% would be 6.6 V. Now because you hope to read values between 45% and 55%, the analogue meter needs to be carefully watched as it records. That's where the Fluke has the advantage, as most Flukes can be set to read min and max values. You may need to research on the web just where on your vehicle the test terminals are. I have noted that some Californian vehicles must be equipped with their own diagnostic LED, maybe yours has this too, in which case you count pulses on the LED to determine a problem. On my vehicle, the earth braid is attached to the chassis immediately on the support bracket for the ignition gear, in Aussie anyway, inside the left hand side mudguard. All the best.
08-05-2011, 01:40 AM
#10
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560 SEC AMG Clone
Megawatt Man,
I have a California CIS-E controller and can't get it in Duty Cycle on/off ratio mode when depressing the #2 button on the x92 connector. No flashing LED either. I also get a solid 0% and 100% DC. Any ideas? I have replaced the O2 sensor and have swapped the CIS-E controller with two others and get the same thing.
Mike
PS: This is my first post here but I am normally on Benzworld.
I have a California CIS-E controller and can't get it in Duty Cycle on/off ratio mode when depressing the #2 button on the x92 connector. No flashing LED either. I also get a solid 0% and 100% DC. Any ideas? I have replaced the O2 sensor and have swapped the CIS-E controller with two others and get the same thing.
Mike
PS: This is my first post here but I am normally on Benzworld.
08-09-2011, 11:17 PM
#11
Junior Member
Thread Starter
http://www.benzworld.org/forums/w124...-reader-3.html
G'day Mike, Please try to excuse this question. Do you have the key on when attempting to read the codes? That's a must and I should assume that if you have got so far as to even attempt to read the codes you are across this essential.
So if you can't receive flashes from the led, I reckon that the LED could have failed , that one of the wires is open circuit or that for some reason the supply voltage to that circuit has failed. You need a wiring diagram to adequately check these things out. As an alternative, you could build the radio shack external reader for a few bucks. That's why the link is given above. If it doesn't respond, we're back to the start. But what are the symptoms? Why do you seek to read the codes? The KE Jetronic system is designed to let you "limp home" in the event of any failure. It is then quite conceivable that supply to the controller/computer has failed, which would result in no output from the on-board code reader, but with that failure would come a whole lot other horrible symptoms. Limping home is one thing but starting, running, accelerating at al would all be problematic. So what are the symptoms? Megawatt Man
G'day Mike, Please try to excuse this question. Do you have the key on when attempting to read the codes? That's a must and I should assume that if you have got so far as to even attempt to read the codes you are across this essential.
So if you can't receive flashes from the led, I reckon that the LED could have failed , that one of the wires is open circuit or that for some reason the supply voltage to that circuit has failed. You need a wiring diagram to adequately check these things out. As an alternative, you could build the radio shack external reader for a few bucks. That's why the link is given above. If it doesn't respond, we're back to the start. But what are the symptoms? Why do you seek to read the codes? The KE Jetronic system is designed to let you "limp home" in the event of any failure. It is then quite conceivable that supply to the controller/computer has failed, which would result in no output from the on-board code reader, but with that failure would come a whole lot other horrible symptoms. Limping home is one thing but starting, running, accelerating at al would all be problematic. So what are the symptoms? Megawatt Man
08-17-2011, 12:51 AM
#12
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560 SEC AMG Clone
Megawatt Man,
Thank you for the reply. I was trying to measure Duty Cycle using the x11 connector so I could properly adjust the A/F. My problem was that I have a California CIS-E control and could not get it into on/off ratio output mode. I finally figured it out and had to hold the button for 2-4 seconds multiple times until the DC changed for 85% to 70%. Once I received the 70% DC reading, I knew it was in output mode. I then was able to adjust the AF mixture on both the fuel distributor and EHA. See my thread on Benzworld for all the details. The breakthrough was at the end of the thread.
http://www.benzworld.org/forums/w126...e-install.html
Thanks again Megawatt Man,
Mike
Thank you for the reply. I was trying to measure Duty Cycle using the x11 connector so I could properly adjust the A/F. My problem was that I have a California CIS-E control and could not get it into on/off ratio output mode. I finally figured it out and had to hold the button for 2-4 seconds multiple times until the DC changed for 85% to 70%. Once I received the 70% DC reading, I knew it was in output mode. I then was able to adjust the AF mixture on both the fuel distributor and EHA. See my thread on Benzworld for all the details. The breakthrough was at the end of the thread.
http://www.benzworld.org/forums/w126...e-install.html
Thanks again Megawatt Man,
Mike
10-09-2012, 08:00 AM
#13
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W116 350SE
ECU wiring
I help a friend to wire a 420 in a 350SLC which has different injection. He must build the electrical harness between sensors and ECU
I am trying to find out the connections to the computer. At what pin goes every wire.
Something like in the picture attached, it's a KE-Jetronic computer but different marque.
I am trying to find out the connections to the computer. At what pin goes every wire.
Something like in the picture attached, it's a KE-Jetronic computer but different marque.
10-09-2012, 06:53 PM
#14
Junior Member
Thread Starter
Reply to STEFAN V8
Hello Stefan, I am unble to expand the gif image to be able to read it because of resolution issues. However I believe it is a pic of the SLC injection controller which operates a mechanical system, whereas the KE system uses the same facilities but with electroniuc control. I therefore believe you will need the controller from the 420 as well as the wiring diagram. isthisdave on this site has a great discussion of functions and checks of wiring but no wiring diagrams as yet.
12-31-2012, 07:31 PM
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1985 190E 2.3
Thank you so much for this info. In about 10 years of browsing specialty forums from RX-7s to DSMs to W201s, I have to say that this is the most useful, well written, thought out, and USEFUL post I have ever come across. Big thumbs up!!!! (I know I said useful twice by mistake, but I'm going to leave it that way 
)
)
01-01-2013, 11:40 AM
#17
Great article MEgawatt. I have same 88 300CE.
That cold start issue is interesting.
Cold start with cold ambient temp and she struggles to start.
I replaced the OVP but with a cheapo (damn their eyes) and noticed improved start (not totally resolved) and better normal running but after awhile the start seems to have gone backwards again. Now yes it could be/probably is the OVP still but wondering. If leads to Coolant Temp Sensor are removed and start issue remains the same does this indicate non performance of said item ? (this was a test suggested elsewhere)
And if I might be so bold, any chance you could do a mini how to set multimeter for each of these test you mention.
I have no electrical background and despite opening and closing the multimeter manual I am a bit confused about what the dial should be set to for the tests you mentioned.
I AM NOT ASHAMED TO ADMIT IT ! :-)
That cold start issue is interesting.
Cold start with cold ambient temp and she struggles to start.
I replaced the OVP but with a cheapo (damn their eyes) and noticed improved start (not totally resolved) and better normal running but after awhile the start seems to have gone backwards again. Now yes it could be/probably is the OVP still but wondering. If leads to Coolant Temp Sensor are removed and start issue remains the same does this indicate non performance of said item ? (this was a test suggested elsewhere)
And if I might be so bold, any chance you could do a mini how to set multimeter for each of these test you mention.
I have no electrical background and despite opening and closing the multimeter manual I am a bit confused about what the dial should be set to for the tests you mentioned.
I AM NOT ASHAMED TO ADMIT IT ! :-)
Last edited by stormtigers; 01-01-2013 at 11:44 AM.
01-11-2013, 12:14 AM
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w126 380 sel, W115 240D, W201 190e 2.6
KE Diagnosis on 190e 2.6
Hi Megawatt Man
Great article, still trying to work my way through it slowly.
I have recently purchased a 1990 190e 2.6 auto sportline,(90,000km only) and driven it 3,700 kms across Australia to bring it home. The first 1,000 km were fine but situation deteriorated as the mileage increased.
My vehicle runs rich (black smoke) and fuel usage increases directly in relation to under bonnet ambient temperature. Cool mornings, early running and I managed 11-13 litres/100km. Mid afternoon fuel stops, 40 degrees plus outside, traffic jams increased fuel consumption dramatically, the worst being 34l/100 in one section 110 kms long. The next worst was 20 l/100 after a hot fuel stop. To keep running I just had to rest in the shade with hood open for half an hour. Driver and car would cool down a bit and I could continue at about 15-16l/100.
The car always ran fine at 110km/hr but as the ambient temperature increased, it became an absolute pig down low. Black smoke visible on idle (when it would idle). Any acceleration produced great clouds of black smoke.
Any guidance really appreciated
Ray (from OZ)
Great article, still trying to work my way through it slowly.
I have recently purchased a 1990 190e 2.6 auto sportline,(90,000km only) and driven it 3,700 kms across Australia to bring it home. The first 1,000 km were fine but situation deteriorated as the mileage increased.
My vehicle runs rich (black smoke) and fuel usage increases directly in relation to under bonnet ambient temperature. Cool mornings, early running and I managed 11-13 litres/100km. Mid afternoon fuel stops, 40 degrees plus outside, traffic jams increased fuel consumption dramatically, the worst being 34l/100 in one section 110 kms long. The next worst was 20 l/100 after a hot fuel stop. To keep running I just had to rest in the shade with hood open for half an hour. Driver and car would cool down a bit and I could continue at about 15-16l/100.
The car always ran fine at 110km/hr but as the ambient temperature increased, it became an absolute pig down low. Black smoke visible on idle (when it would idle). Any acceleration produced great clouds of black smoke.
Any guidance really appreciated
Ray (from OZ)
Last edited by artylinden; 01-11-2013 at 12:18 AM. Reason: Correcting contributor's name
03-07-2013, 07:09 AM
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W109-6.3
Amazing information...
I've recently bought my 1990 300E and I have done much for it till now to make it perfect.
My engine used to work fine, The only bothering thing was very high fuel consumption, So I started checking and found that all 6 fuel injectors are leaking all, and unable to spray the fuel well, So I replaced them with new ones and it seems much better now, engine works very smooth.
Now there is just something that I am not sure about, when I remove the air filter cap, there are some sensors (sockets under) under it, one which is indicated below is believed to affect the engine RPM when detached, So I tested it and nothing happened, I was told it may be a problem of OVP, so I got a new OVP and tested it, nothing changed yet. Then I tested ECU and detached it, and then yes it really changed rpm! it wasn't about my OVP (because same result with my old OVP), it also couldn't change the rpm while that sensor was detached...So I really don't understand why there is no change when I detach the sensor itself only? When I open the switch you can hear a "click" inside it... .
And here is position of air mass plate...
I really appreciate if you guide me to solve this one which is really bothering me, although there is no problem right now, I guess it may be annoying in summer while using air conditioner system.
Best regards
I've recently bought my 1990 300E and I have done much for it till now to make it perfect.
My engine used to work fine, The only bothering thing was very high fuel consumption, So I started checking and found that all 6 fuel injectors are leaking all, and unable to spray the fuel well, So I replaced them with new ones and it seems much better now, engine works very smooth.
Now there is just something that I am not sure about, when I remove the air filter cap, there are some sensors (sockets under) under it, one which is indicated below is believed to affect the engine RPM when detached, So I tested it and nothing happened, I was told it may be a problem of OVP, so I got a new OVP and tested it, nothing changed yet. Then I tested ECU and detached it, and then yes it really changed rpm! it wasn't about my OVP (because same result with my old OVP), it also couldn't change the rpm while that sensor was detached...So I really don't understand why there is no change when I detach the sensor itself only? When I open the switch you can hear a "click" inside it... .
And here is position of air mass plate...
I really appreciate if you guide me to solve this one which is really bothering me, although there is no problem right now, I guess it may be annoying in summer while using air conditioner system.
Best regards
08-13-2013, 03:20 PM
#21
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G wagon 560
G wagon 300 engine swap to sel560
Great work Mr Megawatt Man, Please help, I have put an 560 sel engine in my g wagon300e (ball ache)fit net went well, but it has no power when hot and is like the choke is on constantly. When cold it gos like the wind 
mfor 1 mile then nothing but smelly exhaust ( rich) and no power,
I have swapped nearly everything on the engine even bought a sec 560 to interchange parts:-( no joy. I have checked the earths etc etc.. Confused.com
Please help..
mfor 1 mile then nothing but smelly exhaust ( rich) and no power, I have swapped nearly everything on the engine even bought a sec 560 to interchange parts:-( no joy. I have checked the earths etc etc.. Confused.comPlease help..
10-19-2014, 08:14 PM
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1988 190e
*KE Jetronic Diagnosis
1988 190e CA model
56,000 miles
Sat in a garage in San Diego with 30,000 on it for 15 years.
2nd owner put 20,000 on it from ~2009 - 2014. 2nd owner did not treat this car right.
Since purchase I have put about 4000 miles on this car and replaced several parts and performed a lot of maintenance:
- 53900 - oil change
spark plugs
Shocks & struts
transmission flush & filter
brakes
brake fluid flush
steering stabilizer
flush coolant
front & rear flex joints
drive shaft carrier bearing
all coolant hoses
coolant sensors (2)
flush power steering/filter
cap & rotor & plug wires
alternator belt
motor mounts
transmission mount
OPV relay (on not so good advise)
Complete exhaust system w/ all new mounts
air idle control valve hoses (3)
differential oil change
55240
Discovered water in the oil
Head rebuild
water pump
timing chain tensioner
belt tensioner
all six tie rod ends
alignment
EHA valve (new)
After all of this I have a pretty nice car. Now I'm out to dial in the fuel injection
Per this document: https://mbworld.org/forums/e-class-w...diagnosis.html
I perform the tests and results are as follows:
Temp: 87C
Diagnostic: One flash, #4 LED out
CEL ON! (nothing I have tried will get this to turn off!)
Test 1: Pin 2 -> 6: 12.53 V
I seem to consistently get these results:
Test 1:
Key on, CEL on, #4 LED on: pin 2 -> 3: 1.62 V
depress #2 button to turn off #4 LED: pin 2 -> 3: 10.86 V
depress #2 button to turn on #4 LED: pin 2 -> 3: 3.20 V
(#4 LED still on)
Test 2: Deflect air flow sensor: go from 3.2 V to 9.4 V and back to 3.2 V
Test 3: Go full throttle:3.2 V to 8.4 V and back to 3.2 V
Test 4: Lambda @ 750 RPM: 27%
Lambda @ 2500 RPM: 41%
Lambda increases to 49% after letting off throttle and slowly settles back to 27%
Air flow pot: (car running at idle)
5V between pins 1 & 3.
With no deflection of air flow, .7 V between pins 1 & 2
At this point I stopped with measurements & adjusted the air fuel mixture (Lambda)
I have a meter with duty cycle.
Starting measurement was 27%
~ 3/8 of a turn CCW & I dial in on 49 - 51%.
More to come.
How do I get the CEL off?!?
And thank you Megawatt Man! (I'm an EE)
1988 190e CA model
56,000 miles
Sat in a garage in San Diego with 30,000 on it for 15 years.
2nd owner put 20,000 on it from ~2009 - 2014. 2nd owner did not treat this car right.
Since purchase I have put about 4000 miles on this car and replaced several parts and performed a lot of maintenance:
- 53900 - oil change
spark plugs
Shocks & struts
transmission flush & filter
brakes
brake fluid flush
steering stabilizer
flush coolant
front & rear flex joints
drive shaft carrier bearing
all coolant hoses
coolant sensors (2)
flush power steering/filter
cap & rotor & plug wires
alternator belt
motor mounts
transmission mount
OPV relay (on not so good advise)
Complete exhaust system w/ all new mounts
air idle control valve hoses (3)
differential oil change
55240
Discovered water in the oil
Head rebuild
water pump
timing chain tensioner
belt tensioner
all six tie rod ends
alignment
EHA valve (new)
After all of this I have a pretty nice car. Now I'm out to dial in the fuel injection
Per this document: https://mbworld.org/forums/e-class-w...diagnosis.html
I perform the tests and results are as follows:
Temp: 87C
Diagnostic: One flash, #4 LED out
CEL ON! (nothing I have tried will get this to turn off!)
Test 1: Pin 2 -> 6: 12.53 V
I seem to consistently get these results:
Test 1:
Key on, CEL on, #4 LED on: pin 2 -> 3: 1.62 V
depress #2 button to turn off #4 LED: pin 2 -> 3: 10.86 V
depress #2 button to turn on #4 LED: pin 2 -> 3: 3.20 V
(#4 LED still on)
Test 2: Deflect air flow sensor: go from 3.2 V to 9.4 V and back to 3.2 V
Test 3: Go full throttle:3.2 V to 8.4 V and back to 3.2 V
Test 4: Lambda @ 750 RPM: 27%
Lambda @ 2500 RPM: 41%
Lambda increases to 49% after letting off throttle and slowly settles back to 27%
Air flow pot: (car running at idle)
5V between pins 1 & 3.
With no deflection of air flow, .7 V between pins 1 & 2
At this point I stopped with measurements & adjusted the air fuel mixture (Lambda)
I have a meter with duty cycle.
Starting measurement was 27%
~ 3/8 of a turn CCW & I dial in on 49 - 51%.
More to come.
How do I get the CEL off?!?
And thank you Megawatt Man! (I'm an EE)
Last edited by JoeInBallard; 10-19-2014 at 09:24 PM.
10-21-2014, 01:08 AM
#23
Junior Member
Thread Starter
KE Jetronic
G'day JoeInBallard, I'll have to research a little to answer your question about the CEL. In Oz, our 124s don't have CELs and I believe that they are more concentrated in California than other US States. From memory, the fault code reader is mounted in the vehicle and I guess that you have derived your fault codes from that facility. Again from memory, there is a process for clearing the fault code that might be something like "hold the button down for 10 seconds". I do remember a contributor to the overall effort writing that he had to hold it down for 12 seconds. I'll be back to you.
Incidentally, I was notified of your osting by the forum management and upon opening the page I was horrified to note that a number of blokes have asked me questions about which I have nt been notified!
Best Regards Megawatt Man
Incidentally, I was notified of your osting by the forum management and upon opening the page I was horrified to note that a number of blokes have asked me questions about which I have nt been notified!
Best Regards Megawatt Man
10-21-2014, 01:43 PM
#24
Out Of Control!!
There are all sorts of KE modifications---- vs MY/MD--First what is the VIN??
and by the way you have a model 201---why not post in that group!!
and by the way you have a model 201---why not post in that group!!
Last edited by Plutoe; 10-22-2014 at 01:11 PM.
12-15-2014, 01:25 PM
#25
Newbie
Join Date: Oct 2014
Posts: 1
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MB 300E 24v
enaberg
i have E30024v which have been stalling at red lights and roundabouts only
operating on ideling.I finnaly found the problem and it was the elekrohydralic valv on the fuel distrubuter that did´nt operate correctly some times.The valve was expensive but now the Mb is working nice.
Thanks for the KEjet info on this forum. I also have E300-90 this have made
more than 1 million km and never had this problem.
operating on ideling.I finnaly found the problem and it was the elekrohydralic valv on the fuel distrubuter that did´nt operate correctly some times.The valve was expensive but now the Mb is working nice.
Thanks for the KEjet info on this forum. I also have E300-90 this have made
more than 1 million km and never had this problem.
