SL/R129: 16 Pole Diagnostic Connector (X11/4) 1993 300 SL
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1993 300 SL
16 Pole Diagnostic Connector (X11/4) 1993 300 SL
When testing for faults in the MAS Engine Systems Control (Pole 14 on the 16 Pole X11/4) I get no flashes at all. Clear of faults is supposed to be shown by 1 flash. Actual faults by additional flashes. Why would this test generate no flashes? There is 12V at MAS terminal 30.
This can drive a guy nuts! Any help is welcome.
Thanks.
This can drive a guy nuts! Any help is welcome.
Thanks.
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1993 300 SL
Thanks, Bob. I came to the same conclusion and ordered a new MAS. If that doesn't do it I will probably send the EZL for testing and, if necessary, for rebuilding. There is an outfit in Florida specializing in testing and rebuilding Mercedes EZLs. (I find that the various, used electronic control units sold on Ebay are frequently defective.)
Thanks again for your advice.
Harry
Thanks again for your advice.
Harry
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1993 300 SL
Hi Bob,
I installed the new MAS. It was advertised as new and the correct part number (012 545 48 32. Instead, ProgRama sent a rebuilt unit with a different part number (011 545 83 32) which they claim to have rebuilt to the original part number specifications. On installing the new unit I tested socket 14 (MAS) and obtained a constant light, as opposed to the proper no light and then flashes for faults. Do you think the new unit may be shorted or otherwise not compatible?
Thanks,
Harry
I installed the new MAS. It was advertised as new and the correct part number (012 545 48 32. Instead, ProgRama sent a rebuilt unit with a different part number (011 545 83 32) which they claim to have rebuilt to the original part number specifications. On installing the new unit I tested socket 14 (MAS) and obtained a constant light, as opposed to the proper no light and then flashes for faults. Do you think the new unit may be shorted or otherwise not compatible?
Thanks,
Harry
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
On my car when I make connections the LED (light) is on. Still, if I ground the diagnostic socket for 3 seconds the light blinks-out a code, and then it stays on continuously.
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1993 300 SL
Hi Bob,
I replaced the MAS but still no joy. With ignition on, the check engine light does not come on; Pole 14 (MAS) has a steady light and flashes code 1. Pole 8 (EZL) flashes code 17, crankshaft position sensor - which has been replaced; Pole 3 (EIS) has a steady light with no flashes. Seems the check engine light not coming on when the ignition is turned on and the constant light on Pole 3 indicate a problem, but I'm out of ideas. Your thoughts on what the problem might be would be greatly appreciated.
Thanks,
Harry
I replaced the MAS but still no joy. With ignition on, the check engine light does not come on; Pole 14 (MAS) has a steady light and flashes code 1. Pole 8 (EZL) flashes code 17, crankshaft position sensor - which has been replaced; Pole 3 (EIS) has a steady light with no flashes. Seems the check engine light not coming on when the ignition is turned on and the constant light on Pole 3 indicate a problem, but I'm out of ideas. Your thoughts on what the problem might be would be greatly appreciated.
Thanks,
Harry
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1993 300 SL
Hi Bob,
I did as you suggested and the pumps ran, however, how does that explain the check engine light not turning on? (In reading further about the circuit, it seems that the EZL (ignition controller) simply passes through the RPM signal to the MAS which then distributes it.) In any case, I'll send the EZL to Florida for testing and will let you know what happens.
Thanks,
Harry
I did as you suggested and the pumps ran, however, how does that explain the check engine light not turning on? (In reading further about the circuit, it seems that the EZL (ignition controller) simply passes through the RPM signal to the MAS which then distributes it.) In any case, I'll send the EZL to Florida for testing and will let you know what happens.
Thanks,
Harry
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
Over by the ignition controller is a round diagnostic connector. With the key on I suggest measuring the voltage between sockets #2 and #3. Typically you should read 7-8 volts -- zero volts suggests a faulty controller, but prior to condemning it you would remove the electrical connector to the controller and verify it is being powered: with the key on there should be 12 volts on socket #1.
If normally the engine starts but immediately quits but starts and runs with the MAS bypassed, then you probably have a faulty EZL.
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1993 300 SL
The check engine light is a separate issue, Harry. You may have a faulty fuel injection controller.
Over by the ignition controller is a round diagnostic connector. With the key on I suggest measuring the voltage between sockets #2 and #3. Typically you should read 7-8 volts -- zero volts suggests a faulty controller, but prior to condemning it you would remove the electrical connector to the controller and verify it is being powered: with the key on there should be 12 volts on socket #1.
If normally the engine starts but immediately quits but starts and runs with the MAS bypassed, then you probably have a faulty EZL.
Over by the ignition controller is a round diagnostic connector. With the key on I suggest measuring the voltage between sockets #2 and #3. Typically you should read 7-8 volts -- zero volts suggests a faulty controller, but prior to condemning it you would remove the electrical connector to the controller and verify it is being powered: with the key on there should be 12 volts on socket #1.
If normally the engine starts but immediately quits but starts and runs with the MAS bypassed, then you probably have a faulty EZL.
Hi Bob,
Well, I got the EZL back from the rebuilder in Florida, much delayed by hurricanes. I ran the tests you suggested. At the round diagnostic connector, X11, the voltage between terminals 2 and 3 is only 1.05 volts. The voltage on socket #1 of the electrical connector to the EZL is 12 volts. Could the rebuilt EZL still be defective? Are there other definitive tests I can run? I also connected a test light to terminal 1 (-) of the coil and ground. When the engine is cranked over the light does pulse. I then connected the voltmeter (+) to terminal 1 on the coil and the (-) to ground with a reading of 12 volts, which is supposed to indicate a shorted control wire or driver.
I've worked on cars as a hobby for many years and am not a complete dunce, but the problem with this car has overwhelmed me. Thanks for any help you may offer.
Harry
Well, I got the EZL back from the rebuilder in Florida, much delayed by hurricanes. I ran the tests you suggested. At the round diagnostic connector, X11, the voltage between terminals 2 and 3 is only 1.05 volts. The voltage on socket #1 of the electrical connector to the EZL is 12 volts. Could the rebuilt EZL still be defective? Are there other definitive tests I can run? I also connected a test light to terminal 1 (-) of the coil and ground. When the engine is cranked over the light does pulse. I then connected the voltmeter (+) to terminal 1 on the coil and the (-) to ground with a reading of 12 volts, which is supposed to indicate a shorted control wire or driver.
I've worked on cars as a hobby for many years and am not a complete dunce, but the problem with this car has overwhelmed me. Thanks for any help you may offer.
Harry
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
I would remove the connector to the injection controller and see that it is powered by measuring voltages on the connector. The layout of the connector sockets is shown here. With the key on you should have 12 volts between socket #41 and #19 (ground) and between #1 and #19.
A defective EZL was indicated by a specific set of circumstances: with a new MAS normally the engine starts but quickly dies, and with the MAS bypassed to force the fuel pumps to run unconditionally the engine starts but does not die.
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1993 300 SL
Hi Bob,
You seem to have uncovered the problem. I tested the connector to the injection controller and it has 0 voltage at either #41 or #1 and ground #19. So, thankfully, at least it may not be a faulty injection controller. Do you know where the power is supplied from to the connector? Could it have something to do with the check engine light not coming on?
As always, thanks for all your excellent advice.
Harry
You seem to have uncovered the problem. I tested the connector to the injection controller and it has 0 voltage at either #41 or #1 and ground #19. So, thankfully, at least it may not be a faulty injection controller. Do you know where the power is supplied from to the connector? Could it have something to do with the check engine light not coming on?
As always, thanks for all your excellent advice.
Harry
Last edited by tgroup; Oct 29, 2017 at 05:39 PM.
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
Since the fuel injection controller is not powered, either the over-voltage protection relay (OVP) or its fuse are likely bad. The OVP is located near the MAS. It is square with a red top and a clear plastic cover. If the fuse is okay, then unless the OVP is less than 10-years-old I would just replace it with no further testing. The date of manufacture should be printed on the side of the OVP.
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1993 300 SL
Hi Bob,
The OVP was bad just as you surmised. When I installed the new OVP, the fuel injection controller got power and had one flash on socket 3 (16 pole diag.) On socket 14 (MAS) the light is steady and flashes once more brightly. The only problem is the ignition controller (socket 8) which flashes code 17 (crankshaft position sensor). The sensor had the correct resistances, but while cranking the sensor did not produce a steady AC voltage, but one which fluctuated, never exceeding 300 mv. The specs require a voltage greater than 400 mv. So I installed a new position sensor, but the AC voltage still fluctuates and does not reach 400 mv. Socket 8 still flashes code 17 (I did remember to clear the code after installing the new sensor) and the car still doesn't start. I tested for spark at the coil and at one of the plugs and it seems OK.
Your suggestions are appreciated. Thanks.
Harry
The OVP was bad just as you surmised. When I installed the new OVP, the fuel injection controller got power and had one flash on socket 3 (16 pole diag.) On socket 14 (MAS) the light is steady and flashes once more brightly. The only problem is the ignition controller (socket 8) which flashes code 17 (crankshaft position sensor). The sensor had the correct resistances, but while cranking the sensor did not produce a steady AC voltage, but one which fluctuated, never exceeding 300 mv. The specs require a voltage greater than 400 mv. So I installed a new position sensor, but the AC voltage still fluctuates and does not reach 400 mv. Socket 8 still flashes code 17 (I did remember to clear the code after installing the new sensor) and the car still doesn't start. I tested for spark at the coil and at one of the plugs and it seems OK.
Your suggestions are appreciated. Thanks.
Harry
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
Since you have spark, I would be looking for fuel. One way is to have a fuel line on top of the fuel distributor cracked-open. Run the starter and see if fuel emerges. Another test would be tor remove a fuel injector from the head, re-attach it to its line, and observe fuel spray while the starter cranks.
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1993 300 SL
Hi Bob,
I was using the method for testing the crankshaft position sensor described in a CD for Mercedes purchased on the internet . It says the AC voltage generated by the CKP is tested at cranking speed. Your information about running the engine for the test must be correct. Where can I get the same manual you're using?
In any event there is no fuel supplied at the fuel distributor. I hear the pumps go on momentarily, but then nothing. When I first began to diagnose the problem, I thought the pumps were malfunctioning so I installed new fuel pumps. No joy. I bench tested the old pumps and they seem to run OK.
The MAS is newly rebuilt, so is the EZL. The fuel injection module reads no fault with the new OVP. When I changed the pumps I also installed a new fuel filter, making sure that the arrow pointed in the direction of flow.
So what could be preventing the fuel pumps from running? Is there a fuel shut-off incorporated in the alarm system, or somewhere else? (The car is jacked up quite a bit on its right side, but the fuel tank is half full.)
Again, many thanks for your help.
Harry
I was using the method for testing the crankshaft position sensor described in a CD for Mercedes purchased on the internet . It says the AC voltage generated by the CKP is tested at cranking speed. Your information about running the engine for the test must be correct. Where can I get the same manual you're using?
In any event there is no fuel supplied at the fuel distributor. I hear the pumps go on momentarily, but then nothing. When I first began to diagnose the problem, I thought the pumps were malfunctioning so I installed new fuel pumps. No joy. I bench tested the old pumps and they seem to run OK.
The MAS is newly rebuilt, so is the EZL. The fuel injection module reads no fault with the new OVP. When I changed the pumps I also installed a new fuel filter, making sure that the arrow pointed in the direction of flow.
So what could be preventing the fuel pumps from running? Is there a fuel shut-off incorporated in the alarm system, or somewhere else? (The car is jacked up quite a bit on its right side, but the fuel tank is half full.)
Again, many thanks for your help.
Harry
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'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
All of the diagnostic manuals are online, Harry. See here.
There is no shut-off. The pumps are powered from the MAS controller, and it uses three signals: the ignition switch in the run and start positions, and the engine running status from the EZL ignition controller. When the ignition switch is turned to the run position, the MAS powers the pumps for a second or two. It also powers the pumps while the switch is in the start position and while the engine is running.
I would remove the MAS controller and measure voltage on socket #12 of its connector with the ignition switch in the start position. It should be 12 volts DC; if not, then the ignition switch, the transmission neutral-safety switch, or wiring is faulty.
I would remove the MAS controller and measure voltage on socket #12 of its connector with the ignition switch in the start position. It should be 12 volts DC; if not, then the ignition switch, the transmission neutral-safety switch, or wiring is faulty.
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1993 300 SL
Hi Bob,
The voltage at #12 socket (MAS connector) with the starter cranking is 10.5 volts. Then I bridged sockets 1 and 2 and the pumps ran, even with the ignition switch in off position. Ran pumps for about 30 seconds with fuel line disconnected at fuel distributor, but still no fuel pumped out at all. Do you have any ideas on what could be the problem? Could there be an obstruction in the fuel tank outlet or in the fuel line itself?
Thanks again for all your advice.
Harry
The voltage at #12 socket (MAS connector) with the starter cranking is 10.5 volts. Then I bridged sockets 1 and 2 and the pumps ran, even with the ignition switch in off position. Ran pumps for about 30 seconds with fuel line disconnected at fuel distributor, but still no fuel pumped out at all. Do you have any ideas on what could be the problem? Could there be an obstruction in the fuel tank outlet or in the fuel line itself?
Thanks again for all your advice.
Harry
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
To see fuel the air flow meter flap must be deflected. That occurs if you crank the engine; alternatively, with the air cleaner housing removed you can deflect it with your hand.
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1993 300 SL
Hi Bob,
I ran the test with the air flow meter flap deflected and still no fuel. The fuel flow diagram shows the pump pressure inlet to the fuel distributor is the one without the fuel pressure regulator which is mounted on the outlet. Is that correct?
If I'm testing the proper fuel line, what could the problem be? Should I disconnect the line and check for obstructions? Could it be the back flow valves on the fuel pumps, or some other problem with the pumps, or an obstruction in the tank? (They were very cheap replacement pumps, not Bosch.)
Thanks again,
Harry
I ran the test with the air flow meter flap deflected and still no fuel. The fuel flow diagram shows the pump pressure inlet to the fuel distributor is the one without the fuel pressure regulator which is mounted on the outlet. Is that correct?
If I'm testing the proper fuel line, what could the problem be? Should I disconnect the line and check for obstructions? Could it be the back flow valves on the fuel pumps, or some other problem with the pumps, or an obstruction in the tank? (They were very cheap replacement pumps, not Bosch.)
Thanks again,
Harry
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
With the pumps running I also would crack open the return line and check that fuel leaks. If there is no fuel, then the pressure to the distributor is weak, or I suppose there may be a blockage within the distributor.
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1993 300 SL
Hi Bob,
I jumpered the MAS and checked the fuel flow with the pumps running. Strong flow at the fuel distributor inlet and also at the fuel pressure valve outlet. Then I checked for fuel at an injector. No fuel is getting to the injector. Does this mean the problem is with the fuel distributor, or the fuel pressure valve? Is there a way to test which it is?
What would you suggest at this point? I really appreciate your taking the time to analyze this problem.
Thanks again,
Harry
I jumpered the MAS and checked the fuel flow with the pumps running. Strong flow at the fuel distributor inlet and also at the fuel pressure valve outlet. Then I checked for fuel at an injector. No fuel is getting to the injector. Does this mean the problem is with the fuel distributor, or the fuel pressure valve? Is there a way to test which it is?
What would you suggest at this point? I really appreciate your taking the time to analyze this problem.
Thanks again,
Harry
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
Did you deflect the air flow sensor plate, Harry? If not, then no fuel will flow to the injectors. But if you did, then I presume there is something wrong with your fuel distributor. In that case a Benzworld member who goes by "H.D." can give you far better advice than me.
