problem UNRESOLVED: intermittent non starts in '93 - 300E

Hey all... About a month or two ago I posted a message asking everyone for their opinions and help regarding my occassional nonstart issue in my 1993 300E. The car
would crank and not start, and at other times it would be fine. The car would occassionally die out at an abrupt stop. Well, since that time I've replaced the OVP, fuel pump relay, and had the alternator, battery, and fuel pump checked and they are all fine. Well, the problem still very much occurs and two mechanics are still baffled...one of them being a reputable Mercedes dealership in Chicago (Loeber Mercedes). In all fairness to them, the car starts fine whenever in their hands. Anyway, I am starving for information and desperate for anyone's help. I want to thank everyone for their advice and for sharing their experiences with me when I first posted this problem.
George
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You've dealt with the usual suspects, now its gets more difficult.
You say that sometimes the engine cranks but won't start.
Is the engine then hot or cold?
How do you then finally get it going?
Also, when it stalls upon a sudden stop (of the car), does the engine restart immediately or is there a problem to get it running again?
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These symptoms occur regardless of the engine being hot or cold. The car gets going again when it finally starts, which could be in two minutes or two days. Again, when the engine stop at a sudden stop, it most often then not starts within a minute.

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Have the engine top wire harness checked They were bad from 4/92 thru 8/95. Look for insulation breakdown/cracking
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bet the fuel pump is getting close. is it one you can hear?
mine in my truck cycles for about 5 seconds when i turn it to on before turning it to start.
it is 10 years old things get tired . also something in the ignition could be breaking down.
things never go wrong at the shop. that is why i let them run around in mine for a few days if it is one of the goofy things.
good luck
case
the case, minus a few cans!
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Does the car have spark when it quits and/or refuses to start? My 300TE had these symptoms on 2 different occasions. Once it turned out to be the coil and the other time (more difficult to diagnose) it was an intermittent CPS crankshaft position sensor failure ( CPS is the one at the rear of the block). The output of the CPS can easily be checked with a voltmeter set at AC millivolt setting. If the CPS reading is zero or inconsistent, the engine controller decides to turn itself off - no spark.
The CPS can loosen, get gunked with oil and/or just fail.
Scott D

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Check the Green relay behind the fuse box. My E280 got the same problem, I replaced that with me older c-class's. It works fine now but I need another one for my c-class.
Keith Beast E14 4NS Docklands

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As another poster said, here's where it starts to get difficult because you've ruled out most of the easy stuff.
Now is the time to spend some time with your mechanic and together develop a strategy that will allow YOU to gather the information HE needs to isolate the problem. Something like keeping a remote start switch in the car and temporarily mount a fuel-pressue gauge under the hood to see of you have fuel pressure or not. When the failure occurs, report that data point back to your mechanic and then on to the next step. It's a long slow process, but not nearly as ostly as throwing money at it.
Best Regards, Dave Barnhart 93 300E

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