EmcEmv

I know you all may groan when someone new jumps into the forum with a request for help but I'm in dire straights and I'm hoping someone can at least point me in a better direction.

I have a 1988 300CE in perfect condition with only 80,000 miles on it The VIN is WDBEA50D6JA776694. This car has defied all efforts to fix it for the last 2 years. The car intermittently stalls with the check engine light on. It can be restarted immediately. sometimes it will run for an hour, sometimes 2 minutes. It will do it running in the garage, at idle or on the highway. I have learned quite a bit about the operation of the fuel injection system on this car and I have determined that the stall is caused by both the EHA and the Y6 Idle speeed adjuster being driven by the CIS computer to a bad state and the car stalls due to improper mixture. If the EHA and Y6 Idle speed adjuster are disconnected, the problem does not happen. Typically, this would be caused by a problem with some input to the computer and I have tested/replaced every sensor and looked at all the inputs with a scope and I cannot find what is causing this. I have also replaced the computer with a used unit with no change. The ECU has also been replaced. I am beginning to wonder about a problem in fuel pressure causing the EHA and Idle adjuster to try and compensate. Both fuel pumps have been replaced and the fuel filter. I am looking for advice on how to test the fuel pressure and where I could get a pressure gauge with the proper adapters for this engine. Most importantly, I have heard through a friend in Germany that there is a known problem like this with the USA version of this car. I have attached a pdf file with full details on what has been done to try and fix this problem. Any advice would be greatly appreciated.

russ.w

I have all the same conditions and am just starting to test the different parts. All I've done so far is change the fuel filter but will try disconnecting the parts you mentioned. It has been a couple of years since you posted so you are probable long gone but if not, let me know your out come - and on the fuel pressure gauage also. russ

EmcEmv

Russ

I'm still around and so is the problem. I have never been able to fix it, car has been in the barn since. We are moving next year so I will be at it again as soon as the weather gets warm. If you have any success, let me know!
Bruce

russ.w

Sorry it took so long to get back. I printed your pdf and will take it a European mech around here to get his input, even though he said a match would be my best fix. I kind of agree but I would bet that when we solve the problem, it will be ######. I'm waiting for some warmer weather as I don't have a garage but will start replacing from the cheapest up - the parts you have tried. There is another fellow that I will be talking to tomorrow that might have some suggestions. So far I have had the plugs and wires changed and a tune up. I replaced the main fuel filter and fuel control modual from ebay to no success. It seems, because 1988 is so long ago, ebay is about the only place I can get parts around here (Cranbrook BC Canada) Anyways best of the New Year and to success!!!

EmcEmv

Hi Russ, thank you for what you are doing, maybe we can solve both of them !! Don't know if I said this but mine also does it with the oxy sensor disconnected. I think it's important to do the troubleshooting with the sensor disconnected so that the computer is open loop. One thing to check is the altitude sensor, it's a small plastic box up in compartment where the computer is, up by the base of the windshield, you can just disconnect it and see if it is better. If I disconnect the cold start valve after I get it started and also disconnect the EHA valve, it will never stall. The computer is driving both of these valves crazy and then it stalls, the question is why is the computer doing this?

Bruce

mohd.awaly

guys i had a similar problem in my garage a few weeks ago , the car shuts down as if it ran out of fuel , sometimes it happens twice a day and sometimes once a week ....

well the problem was in the wiring , some wires were barely connected ...
since you changed all these parts and the problem persists i recommend taking a look at your wiring im pretty sure your problem lies in there .

EmcEmv

Mohd

Thanks for your comments, I have thought about the same thing, I have pulled and pushed on all the wire harnesses in the engine compartment with it running with no difference. I agree that this is likely to be the problem, I will check this again carefully.

russ.w

If you go on ytube there are a lot of videos about this stuff and the ones from mercedessource seem to be good. I'll try some of his downloads and see if they're worth while. Russ

russ.w

Hi Mohd. Are you talking about the spark plug wires or some where else. I have the same problem but the problem occurs before and after I put in new plug wires. russs.w@shaw.ca

mohd.awaly

No my frnd . I mean wires coming in and out of control units .. just follow the cps wire it leads to a control unit then this control unit leads to another .. its all on the left side

E55Greasemonkey

Try and replace the overvoltage protection relay.

Shifter

+1

mohd.awaly

Isnt that the big relay behind the battery ???