'88 300ce starts great when cold. When warm it starts then quickly dies on first try. Then will reluctantly start on second try. Runs great, idles a little rough. Any thoughts why it would be doing this. One suggestion was the tempature sensor was bad and flooding the car each start thinking it was cold.

Most likely what you don't want to hear. Others will agree and some will have suggestions. One person recently said "It's the nature of the beast" - "You can start throwing all kinds of parts at it to find out it still does the same thing". (Paraphrased).

You can search the archives but many of these cars (Including my current one (89) and my 2 previous ones 87 - 91) have done the same thing. (Not the rough idle though. The warm start / die then re-start just seems to be common with these.

I've had temp sensor, oxygen sensor, Tune-up, Vac hoses, Fuel adjustments, EHA valve etc. Runs fantastic, great gas mileage but the same "issue" as most others..

Lots of possibilities to include:

engine coolant temp sensor
fuel accumulator
fuel injectors leaking down

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'91 300-SEL

I have read other post that have had the same problem. Some have mention OVP? What does that stand for and could that be the culpret?

Theyy're teling me it's an intake manifold leak. mine is in the shop right now. We'll see if that's true...after a fuel filter, a fuel accumulator, two fuel lines and a fuel relay, I took it to another shop. Try spraying some starter (ether) around the base of the injector distributor while it's running. If it speeds up, you probably have an intake leak.

Not an uncommon "problem", and there may be nothing wrong. Get in the habit of giving the throttle a little kick once it fires on a hot start and it won't die.

Run whatever diagnostics you want, but I would not recommend replacing parts, apriori, unless you find something that is definitely out of spec.

Tough cold, not hot starting can make the OVP suspect, especially if the ABS light stays on.

Duke

same thing here, with added throttle it stumbles for a number of seconds, then smooths out and is fine. without any throttle application, it dies immediately once, then will start without throttle app on the second try. i have had this problem for at least 100k miles and have never been able to figure out what it is. fuel pressure is in spec, replaced injectors several times to no avail, fuel pump replaced to no effect either.

at this point, i figure the only way to get rid of this problem is to get a crate motor.

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Jonathan
1998 S600
2001 E430
1994 E320
1991 560SEL
1994 Turbo R

This is a common problem this time of year and is most likely caused by 'winter grade' gasoline in warm weather causing excessive vapor bubbles in the fuel lines.

Only way to 'cure' it is to put a timer on the fuel pump to run it a few minutes after shutdown to cool it off. You might also try letting the fuel pump run until it shuts off before cranking the engine . It may 'flush out' the vapor back to the tank enough to allow a good first start.

The accumulators job is to prevent vapor. If you have vapor, then perhaps the accumulator is not up to task.

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'91 300-SEL

on my "hot start" problem, sometimes it will NOT start...period. Try all the coaxing, pumping, etc you want, it just won't start. Accumulator was replaced to no avail. I'm hoping the intake leak will cure the problem. I never had it until recently.