QuestionMy 1978 280ce (entirely euro spec) Mercedes is very hard to start when warm. Very well maintained (new wires OEM cap, injectors, check valve). Recently tested fuel system apparently: 28 psi cold control pressure and warm control pressure; line control pressure dropped to 0 psi in 15 minutes, blocked check valve dropped to 0 psi in 15 minutes. Thus the new injectors (new seals not installed though) and check valve recently installed, which slightly improved the cold start time. I've owned the car since 1990 and stored it each winter. For the first few years it started up immediately each spring. All of a sudden one year it was a little harder to start, then gradually over years got a little worse. The last couple of years the engine has been really shaky on the cold start and the colder it has been the harder it has been to start, but, when it catches and smooths out its perfect. Except; very recently it has become very difficult to start when warm or hot. My most recent experience has been that I went for a short drive, got the engine warm then shut the car off for about 20 minutes. I turn the ignition key and the engine cranks well and fast for a 7 - 10 second period - which is as long as I let it go, then I stop for a few seconds, try again, a third time then it shudders a bit and gradually catches similar to the cold start. Runs great after. What's up, WUp Reg, accumulator?
thnx my man
AnswerKjet symtoms are tough to diagnose by email! Every part is interelated!
BUT
Sounds like you may have a control pressure regualtor issue or fuel pump check valve issue.
Cold pressure seems high ( 21 for that car) , warm should be around 48-49 and rest pressure should be around 41 and should not drop below 20 in 15-20 minutes.
here are other reasons for hard hot start
-loss of rest pressure - most of the time this is a defective fuel pump check valve
-air flow sensor not adjusted
-sticking or binding control plunger
-leaking injectors
-leaking cold start injector
-shorted thermotime switch
