reigelser did pass the time by typing:
> To start the car I have to crank it once for a short time. Even If I crank
> longer it won't start. Then I turn the ignition off completely and start
> again and runs immediately. There was no service done prior to the Check
> engine light coming on. The wiper voltage seems very smooth and stable. I
> haven't measured the supply voltage while having the engine running yet.
> Everything else seems to run good: idle speed, kick down response. So would
> you recommend an engine cleaning first (engine compartment wasn't cleaned in
> a loooong time) and then a rework of the connectors?
> Thanks for all of your advice.

What your describing may be a fuel delivery problem caused by either
the pressure regulator or check valve failing. Try this;

Turn the key on, but don't crank.
Turn the key off, wait a sec
Turn the key on, wait for the fuel pump to stop buzzing
Then try starting the engine.

If the engine fires up your problem is fuel pressure leaking
down. Diagnosing that further is slightly complicated but a cheap
fuel pressure gauge screwed into the fuel rail will indicate a leak
if it drops more than 5psi in an hour. The rail should hold pressure
for more than a day.

--
DougW