So my engine has been running very rough. It idles fine but if you punch the gas it completely bogs and if you slowly increase the throttle it gets to about 2500 and refuses to rev any higher. I've replaced basic things
Bosch Disturber Cap
Plugs
Rotor
All Vacuum lines (has 16inhg at idle)
Fuel filter
Injectors and seals
I've checked fuel pressure and it has 80psi at the upper chamber. It has 71 psi in the lower at idle.I've checked the duty cycle and it varies between 40 and 50 percent. However if you measure straight voltage at the pins it is between 1.5 and 2.3 volts??? No amount of mixture screw adjustment changes it. Im kind of at a loss? When the car first starts it measures 6.7 volts for the duty cycle then quickly drops into the closed loop around 2 volts and varies. What next steps should I take?

 

Not sure of your complete engine setup, but did you check your PCV valve for clogging?

 

These engine don't have a PCV valve just a hose. It's not clogged though.

 

Your measurement does not make sense, or you have a grounding problem with the set-up. Best is to have an oscilloscope to actually see the pin3 to pin2 signal instead of guessing but in absence of that:
Do us a favor and with the same set-up in which you are measuring 2-3 volts when the duty cycle is in the order of 40%-50%, switch the voltmeter to AC mode and tell us what that is.
So since you will repeat the measurement, post all 3 numbers at once:

Duty cycle
DC average voltage
AC rms voltage

with the same set-up.

You might want to post 2 sets of numbers. When engine is cold (so Duty cycle should be 50% at this point) and after operating temp is reached.

 

I have a copy of Bosch's Automotive Electrics/Electronics Systems (c. 1988) that has a chapter on the KE-Jetronic system. I'll send you a pdf copy if you'll PM me your email address.

 

So I borrowed at friends meter the read duty cycle mine does not. When the engine is warm and first starts the voltage reads 6.93volts DC at idle it does not fluctuate till it enters the closed loop. I did a fuel flow test and it gave 250ml in 15 seconds, half of what it's supposed too. However the pressures are ok. There is 14v at the pump. I cleaned all the grounds as well.

Closed loop at idle:... Under 40f: ........Operational temp:
​​​DC Average Voltage: .............3v. ..................2.5v
AC RMS:................................ 5.5v................... 5.2v

Closed loop at 2500:

DC Average Voltage: .......................................1v
AC RMS: .................................................. .........4v

 

Thanks, good data. There was some conflicting information in your first post. This clears up the picture .... a lot.
No contradiction in your lastest DC voltage/AC rms voltage and Duty cycle numbers. I will comment in no particular order:

(1) -16 Inch-Hg Vacuum. That is decent not perfect. Probably not your issue. -17Hg is when the economy gauge get's pegged if the meters are in spec. And a healthy engine should be 17Hg or better. Yours is close and it could even be meter's calibration. No worries.
(2) Your Duty cycle at 40c should still be at 50%, not sure why it has moved to closed loop so soon. Again could be an issue with the reporting. Mine tends to go close loop somewhere around 70-80c for example.
(3) Your pressure indicate a problem with the adjustments. 71 psi = 4.89Bar, 80 psi = 5.51Bar. That is out of spec. Please confirm you used one pressure gauge (differential gauge) to measure this as using to seperate meters would be futile.

If this measurement was made with one meter the differential should be in the range of 0.4 bar, yours is 0.62 par. To my knowledge this is a lean setting meaning the EHA is overworking to increase the fuel/air ratio. The duty cycle measurements also show this.

Assuming there are no other issues like a FD malfunction or injector issues, both your EHA and plunger adjustment (called mixture screw) probably needs to be tested and re-adjusted. We do no know the history so do not know why this happened. These things do not go out of alignment on their own.

Just remember the adjustments are very small steps every time and very granular. I would say no more than 1/8th a turn at a time.
Everytime you adjust you have to keep checking the fuel pressures and check things at idle and 2500 rpm to make sure the two are within +/-10%, hopefully a lot less. Yours is over +10% (2.5V --> 1V)

But before all this can you tell us the history of the FD and the EHA?

Also, are there any error codes? Your duty cycle is nearing it's limit of enrichment which may throw a code. Let's also remember that 2500 rpm with no load is not the same as 2500rpm with load, so under load that duty cycle must be at the limit which is probably why the engine is bogging down.

So maybe pull some error codes form your diagnostic port first.

- Cheers!

 

It ran ok for awhile but slowly it keep getting worse . The distributor cap was absolutely toast on it so I figured that was the issue. Replaced it along with plugs, rotor, injectors, and vac lines. That fixed my hard misfire but it lacks so much power, top speed is about 45 lol. The fuel distributor I have no idea it did run fine and it has not sat for more then a couple days while I've owned it. I took some current measurements from the eha valve.
Ignition on: 20ma
Cold idea: 13ma
Warm idle: 10ma
Coil resistance: 20ohms

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https://streamable.com/un251p?src=player-page-share

That's me giving full throttle then letting off a little at the end. Yea it backfired through the intake. The meter is reading eha current draw.

https://streamable.com/pwo5r6?src=player-page-share

The meter is reading duty cycle in DC. The car is in a open loop and still runs like poo. If I give it full gas it bogs but if I slowly increase throttle it will follow till about 3000 rpm.

https://streamable.com/b83ucf?src=player-page-share

The meter is reading duty cycle in DC. This is what happens when the closed loop kicks in. Voltage drops hard. It still bogs either in closed loop or open.

I feel like it's a fuel pressure/flow issue

 

Your link did not work.

Warm idle 10mA is not good. It should be cycling between -2mA and 0 if perfectly adjusted.
You can try to adjust it back.
Also make sure your coolant temp sensor resistance at temp is correct.

I'm pretty sure you also need to adjust the EHA but first bring the Warm Idle EHA current back down to 0, or just to negative to -2mA in your case.
Make sure the adjustments are very little at a time, but you will be monitoring the EHA current anyway.

It is best to also have the fuel gauge connected while you are doing all this. The delta needs to be less.

You should do this iteratively, adjusting EHA and plunger screw, but only adjust the plunger first to see if the car does better after the first adjustment.
If it is not, after you get it to -2mA, I would stop and think it over.

Are there any codes stored in the ECU?

 

I've read a little about diagnostics on these cars but it's all very conflicting info. How do I access the codes? Does it even store codes it's from 1986. There's no OBD1 port.
I updated them again they should work.
Fuel gauge is connected just really low on gas
Sensor all the way at the back read 1.19kilo ohms. I don't have a temp gun so I can't verify but it seems in spec.

 

I tried adjusting the warm idle eha current draw down the lowest I could get it was 5-6 ma. That was by pushing the plunger all the way down till I was almost moving the air flow plate. Max rich mixture adjustment.

So I measured the O2 sensor reading at a warm idle and it was reading 25 mv. Also when I unplugged it the light did not appear on the dash however the bulb I know is good. So I'm pretty sure it running lean and is not able to compensate with the eha. I'm not 100 percent sure if the O2 sensor is good. However when it is unplugged the car still has the same issue.

 

Yes it sounds like you can not adjust yourself out of this. O2 sensor should be cycling between 100mV to 900mV.
Your system fuel pressure is normal, so I am guessing either the EHA is badly adjusted or malfunctioning.

Without adjusting anything, can you unplug the EHA as the car is idling and tell us what happens?

86 is the first year this model was introduced, it may not have the diagnostic port. Is there a small 9 pin connector between the coolant reservoir and the battery with a lid on it?

 

When the eha is unplugged its idle drops and runs even more rough. There's no connecter. I don't really think it's the eha. The fuel flow was pretty low but the pressure was still good. The control pressure was also lower. I replaced the screen filter before the FD.

I'm really not sure.

 

There are two things that decide your system pressure - control pressure differential.
(1) EHA
(2) Fuel Distributor itself

When you unplug the EHA it goes back to all mechanical adjustments and the fact that it runs even more poorly (super lean) is another sign that one of the 2 items above is the culprit.
In an operating and adjusted FD/EHA, when you unplug the EHA the RPM's may change a bit but engine would run just fine at operating temp.

If you believe your Fuel Distributor is good than it just leaves the EHA. It may be way out of adjustment.
What is the history of the EHA? Was it swapped in used?

 

TheMercedes>>> Sensor all the way at the back read 1.19kilo ohms. I don't have a temp gun so I can't verify but it seems in spec.

I missed this in my first reply:
I believe this is also incorrect. At temp it should be around 0.3K ohms. Check into this. Even though your model year is very early you should have 2 thermistors.
It may be that yours has a common ground (3 pronged) instead of individual grounds (4 pronged) for later years. Still there are 2 thermistors and you should measure both to make sure at least they are in agreement. One goes to you gauge on cluster and the other to the ECU.

 

I've only owned the car for two months. I can tell that the previous owners did not keep up with any maintenance and did things very cheaply. I don't know the history of the eha but I think it's in working order. I'm going to rebuild the FD and go from there. I'm not sure how it could of went bad. I'll check the temp sensor later.

 

At this point I would not attempt to rebuild the FD. Particularly because you do not have any experience in this. You will need some tools to test the distributor after the rebuild. It has to deliver the exact amount of fuel from each port and be in spec. You can imagine what would happen if it does not. Also we are not even sure if it is your FD.

Another point is to my knowledge (I am the original owner of my car) an FD generally has catastrophic failures at the END of Life. Not what you are experiencing.

-Have you measured the fuel delivery from each injector by placing a jar at the end of each injector and looking at the spray pattern and the amount of fuel delivery as you crank away?
-This should have been done after the fuel injector installation because there is a large number if defective new injector parts out there. This may even be your problem.

-Since you are willing to rebuild the FD you should first try to adjust the EHA by taking it off, marking in which position the adjustment screw is followed by turning the screw in the correct direction one half turn in your case. And retesting the EHA current. You will most likely have to re adjust the FD plunger adjustment screw as well assuming the duty cycle/EHA current is improving towards -2ma when you do the first experiment.

Because you do not have the history, it is more likely then not the previous non-care taker even messed up the EHA adjustment or swapped one in from a junk car etc. The EHA and FD go hand in glove, one can not just throw in one of them without testing them a complete unit.

Also the rebuild specialist company will do all this properly using their tools.

All this being said, I'm afraid you are going to paint yourself in a corner that you can not get out of a "non start condition".

Finallly, CISflowtech is the company to trust for rebuilding an FD. They are not cheap, but they are the place to go to for the FD rebuild.

 

So as it turns out it was the fuel distributor. I had a shop swap one from a car they had and it ran great. Very weird considering the car idled fine.

 

Good to hear. My original went bad at around 155K miles. Had to swap in a known good FD and has been great for the last 55Kmiles so far.

- Cheers!

 

BTW, that is not too surprising. (Unless there is a catastrophic failure) if the FD does not work to spec based on EHA adjustment of fuel pressures of lower chamber and system pressure one can still adjust things for one point of operation which is idle where these adjustments are generally made. One can thru mechanical means make the fuel air ratio correct at idle. However when the car needs to move off that one data point and cover all conditions a failing FD/EHA would give you trouble.