When your car is "turned off" the electrical connection to the cold start valve has no electricity. Therefore, there's no injection unless that injector leaks a little. The leaking fuel, however, would just reside in the connector hose and not really get to enough cylinders to flood anything.

What is possible--and probable--is that your 6 normal fuel injectors are leaking residual fuel and flooding your engine. Several of the six will have direct access to an open intake valve of your stopped engine.

In normal use the cold start injector gets a short (< 10 sec) signal from the engine computer to function to help with cold starting. The engine computer gets information from a temperature sensor that verifies the engine is indeed cold. It seems quite unlikely that an electrical failure mode would result in continuous action of the cold start injector, but rather the opposite, i.e. no injection at all. But if it does, then the solution is to test the temperature sensor to determine whether it's telling the computer the engine is always cold. Even if it does, all that should happen is a rich running mixture and hardly a mixture so rich as to prevent starting.

You can chase this unlikely solution all you want, but you'll very likely come back to replacing six fuel injectors.

Of course, to verify flooding, try cranking warm engine with the accelerator pedal down about halfway or more.

Finally, with the cold start injector wiring disconnected, you'll move your starting problems to cold starting, too.

__________________
Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles

89 300CE 181K

I have occasional start problems. But it will always start after about 5 seconds of cranking with the accelerator about halfway down.


does your suggestion above mean that I have leaking injector(s)?

Thanks

Somewhere Merc says that 4-5 seconds cranking can be considered normal. If your injectors are 181K miles old, an improvement could probably be noticeable. Replaced ours at ~140K and warm starting improved to close to immediate with no open throttle.

__________________
Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles