My 300E started dying on me in a completely random fashion. The research I did said it's probably the fuel pump relay. I replaced that to no effect. A little more digging and it was clear that my wiring harness was toast and it was probably the cause. That was replaced and everything was fine for 200 miles and then back to the same problem. The mechanic who has been in the biz for 30 years and owns the shop says it could be anything, but doesn't seem to know how to diagnose the problem. I have to believe that with all these cars still out there someone has had the same problem and figured out how to cure it. HELP!

failing or improperly grounded coil...why fresh harness might have worked for a while..lower impedance may have allowed the coil to still function at minimum for a bit more time. Make sure to install fresh non r plugs, and new ignition wires as well....

Search "OVP relay"
There was a change on that part and will cause your complaint.
If you have the old # part, change it regardless.

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A Dalton

"I have to believe that with all these cars still out there someone has had the same problem and figured out how to cure it"

You know that the solution to the numerous issues that cause that specific syptom always get fixed. The more intermittant the harder. If you are to the parts throwing stage that OVP would be the cheapest first choice. I wouldn't worry about coils as that car has three of them and one won't stop you only make it run bad. I'd throw some fuel pumps next.

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

I have the same EXCAT issue with my 1995 S300. What I have noticed that:
A. Problem is intermittent
B. The engine dies when I get off of the Freeway (after going really fast, if I suddenly stop, chances ARE THAT MY ENGINE DIES).
C. After the engine dies, I turn the car off then on and everything fgoes back to normal (I guess that's Control lt Delete to reboot my car!)

Any advice appreciated

Thanks for the input thus far. Here's a little more background that might help. Car is a 2.8 model with 172,000 miles. I have had this problem for months now trying to sort it out. Besides this problem it started running rough and the mechanic found a bad coil and replaced it. Car was smooth as silk after that except for when it dies. Typically this happens half a dozen times every 100 miles. One time when it was about 110F outside it died 7 times in as many miles on the freeway. First I would pull over and put it in park and it would start right up. The hotter it got the harder to start. Sometimes it would take a dozen cranks to catch. Now with the new harness it's back to starting right up after dying. The mechanic listened to the fuel pump and said it sounded ok to him. SOP is driving down the freeway at 70 and then engine just quits and tach immediately drops to zero. No warning, no coughing, no nothing, just quits. Thanks again.

And what is your OVP relay part number?

Next time it won't start right up, give the OVP a few taps..
..and as I said before , see if your car still has the old style OVP in there ..that is direct 12 V power feed for the Engine Management and a fault there will result in your condition.
The old one is 000-540-52-45
The upgrade replacement is 000- 540-67-45
It is behind the panel, behind the battery.

Also, do you ever see a flicked of the ABS lamp????? If yes, that makes OVP evem more suspect , as that same OVP is also ABS module feed.

Troubleshooting a 94 E320

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A Dalton

The car in question is DIS coil/over Waste Spark ignition, so chalk that.

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A Dalton

Alright, I found what appears to be the OVP. It's got a 15amp fuse on top and says overload on it, but the only coding says K.A.E. 3.901.320. Per another post I tried the technique of turning off the ignition at speed and then turning it back on when the car dies on the freeway. This worked like a charm, but doesn't if I'm in traffic. I did actually over do it once where I turned the key all the way to crank mode and the car started up again when going about 30mph. I hope that's not harmful. It now seems that the car is more difficult to start if it dies while stuck in stop and go traffic as opposed to the freeway failure. Regarding the ABS light, I do remember it coming on in a very dim fashion and then going out some time ago so I'm going to replace that OVP and cross my fingers.

That's it. I'll bet when you take it out you'll find a part number.