I am having problems with my late 80's 300E. Here goes: The car will be running fine, then I will turn the car off at some point during the day. Then when I try to start the car soon after turning it off, the engine will turn over but not start. Then after the car sits for some unspecified time, it will start again as though nothing is wrong. Less than two weeks ago when this happened my mechanic replaced a rather costly fuel pump relay to try and fix the problem....it did not work because the car did the same thing yesterday and would not start till this morning! When the car is running, it performs just fine.. Please give me your advice, thanks so much!!!

Had the same problem on my car. It turns out that the fuel regulator was bad. Have that checked out. Good luck!

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89 300CE
91 Supercharged Miata
99 E320 Wagon

Also do a search on "OVP" or Overvoltage Protection Relay...a faulty one is known to have caused "hot start" problems (i.e., hard to start when engine is warm)...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

I'll sell you my new OVP relay for half the cost if you think that's it (didn't use it after testing). Obviously, it wasn't the problem on my car (fuel pressure regulator).

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89 300CE
91 Supercharged Miata
99 E320 Wagon