Had similar problem, Replaced Coolant temp Sensor;Its a Four Pin plug,tucked in at the rear of the Head , A real b## to get at , Need a tubular socket; Other wise try adjusting EHA

Yea, I just replaced the coolant temp sensor - which is really easy on my M104 motor - right in front! And, I have been advised to NOT adjust the EHA - that all that does is cover up the real problems.

ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

Thats strange, Mine is at the rear ! with Four Pins !! Are you sure you had the right one !

Cal, over the past 6 years the ignition control units failed on my daughter's 1991 300CE and our 1992 300CE. In each cast the engine wouldn't start. Granted that's only a small sample, but that's my experience.

Ryan, suggest biting the bullet and having the Service Department at your local MB dealer troubleshoot your car. Of course that presumes they have an experienced tech who works on 124 cars. Once you learn what's wrong then you can decide whether you can handle the repair, or the repair requires their expertise and equipment. It would be ideal if you had a normally running 300CE that you could swap parts from. I own two 300CE's (1991 & 1992) so I have that luxury. In my case I installed the ICU from the car that wouldn't start into the one that ran fine which caused it not to start. Bingo ... a failed ICU.

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Fred Hoelzle

Therein lies part of my problem - I've had a hard time finding anyone locally to work on this CIS-E fuel injection. They tend to want to swap parts and charge the customer...

Is their an answer to the following question (or even a set of answers):

What would cause the car to stay in open loop, running rich all the time? )I think this is what is happening here...

ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

Ryan, are you saying there isn't a MB dealer, a MB-trained tech at an independent shop, or someone who owns a 1991 300CE near you? If so, that's a bummer.

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Fred Hoelzle

I'm in something of a transition phase - a good independent mechanic friend of mine recently passed away (he has been my 'go to' guy for 20+ years). There are 2 other independents in town - one I don't trust and one that is "reluctant" to work on these 20 year old fuel injections. I will check with them tomorrow...they are usually helpful and might be able to offer some assistance.

The dealer isn't really an option - they were way too expensive for anything that I might want done on any of my old cars...

Ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

Pulled all 6 spark plugs today and they all look perfect - nice and tannish, no oil, not wet, etc.

Don't know what this means for sure, but I thought I might one or more fouled due to a leaky injector...maybe.

I did ruin one wire in removing it - anyone know how I might just get one wire somewhere? This is a pretty new set of wires...

Also pulled the O2 sensor and it looks black - not real "sooty", but definitely black - which rubs off...

ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

Ryan, it will be money well-spent to have your local MB dealer diagnose the problem with your 1991 300CE. Once they let you know exactly what is wrong then you can fix it yourself ... instead of continuing the trial & error method.

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Fred Hoelzle

My 20 years of chasing starting problems says injectors, injectors, injectors.

DG

Hi Ryan; Did you Ever FIX Your Problem !

NO! I have several more recent posts following up the problem (search my username)...haven't had any real luck. That's the advantage to owning 4 old Mercedes - I usually have another one in decent shape (actually all 3 of my other cars are running great - knock on wood)!

I have it parked in the garage and may take it to an Indy after the holidays. It's been very frustrating...

Sorry!

Ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

Thats A Bummer .