Well guys I still have the same problem of plugs fouling out after about 5 miles. Take them out and there black with soot.
I've changed almost everything, Fuel distribution unit, EHA , idle control, ignition unit, plugs, wires, cap and rotor, fuel filter. Duty cycle is at 43-52% at idle but rev it up and black smoke comes out the tail pipe, I have checked for vacuum leaks and thanks to MBDOC I found a big one, fixed it, but it made no difference to the problem so here's my question. Do the injectors wear out? I' have no idea what the mileage is. The vehicle is not trashed or anything like that but I've no idea what its previous life was. It seems strange that if thats the case all the injectors have worn out equally, as each plug is uniformally sooty.

Michael

yes, they do go bad, but usually that means leaking at idle and dribbling.

Have you had the fuel pressure tested correctly? If you have a bad pressure regulator, they will often flood out, ditto for a bad diaphragm in the fuel distributor.

Is the idle mixture set to give you nearly 0 mA at the EHA at idle?

Cold start valves have been known to leak, as well, but that won't give you good idle and flooding on acceleration.

Have you verified that the idle switch is indeed working and that the oxygen sensor is good and functioning? Have you replaced the over-voltage protection relay?

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks for the input Peter.

After the car starts I have disconnected the cold start valve, The 02 sensor is new, I slackened off all the accelerator linkage making sure that the idle switch closes and tested it with a meter for continuity, OVP relay seems okay, I have resoldered all the connections. I have made up a lead to check milliamps at the EHA . I'll post readings and results.

Thank you all for the input

Michael

What is your duty cycle at 2500 rpms? The important thing about this test is to see if fuel control exists beyond the idle condition.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Now we have new changes.
The duty cycle varies between 28.9 - 32.5 at idle but at 2500rpm it settles fairly solid at 52.6 - 54.3.
Now at idle if I try to measure the milliamps at the EHA valve and I don't just unplug it but connect the meter in series then break the line the motor dies. Just to get the basics right which line in the eha valve am I connecting in to , the brown or the other?

Michael

Polarity of the EHA connection is imparitive. Reversing it will creat a real strange set of conditions. Disconnect the EHA and make the engine run properly with basic mixture at the 3mm adjustment.

Not sure how to tell polarity but if I suspected a problem I would reverse it. Key on engine off should be 20ma positive, but it will read 20 anyway.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Okay the eha is disconnected, I have tuned the car with the 3mm allen wrench, (seemed like I had to richen it up to run). The duty cycle still reads 28+ - 32+% (is it still in the loop?) and why the same numbers even though the eha is disconnected? Will it start when cold? I have reconnected the cold start injector.

Michael

There can be no closed loop with the EHA disconnected. I believe the duty cycle should react to the fixed mixture and walk off the scale trying to correct.

The way to calibrate your reading with duty cycle is to disconnect the O2 sensor. The duty cycle should read exactly 50% then. If it is anything else you have either a testing (intrument or connection) problem or a system problem. It is ever so important that one calibrates ones testing before drawing conclusions.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

I was able to use the car today for the first time without it fouling out. I am running without the eha valve plugged in. It did take a lot of cranking to start, but once running it seemed good. What's my next step?
The meter I am using is a Sears just a few weeks old.
One other question what should my rpm's be at 70mph, I'm not sure if I shifting into high gear. I did slacken all the throttle linkage when trying to fix the fouling out could I have upset the gear change settings?
I really appreciate this help from all of you. I now have a car I can drive, now to tidy up the loose ends with regards to the eha valve etc.

Michael

A humble suggestion, recognising that there are people posting here who are far more knowledgeable than I: Is he not getting a fixed 30% ratio at idle, indicating a coolant temperature sensor problem?

Andrew

Thanks for the input ajme,
I have measured the coolant temp. sensor through its range from cold to hot and it follows the graph in the Mitchell on demand as regards to the resistance. But it does seem as though the duty cycle is pegged at 30%.
As posted I am now running without the eha connected and it no longer fouls the plugs, I'll run like this for a couple of days and check condition of the plugs. If they look good I will re connect the eha and see what happens.

Michael

After running the car for 2 days with the eha disconnected I plugged it back in and all the old symptoms came back. Black smoke from the tail pipe and sooty plugs?????

bump

Well I'm stuck with it only running without eha.

I like the car a lot but I hate things that are not correct. I will re test fuel pressure and read the milliamps on the eha again.
thanks for the help guys.
Michael