I have a starting problems when sun shines and weather gets warm after the car has been standing still for a period. In cold weather it starts immediately (which is most often the case here in Denmark).
I belive it is the well known problem of the fuel system loosing pressure, causing gas vapours in the system. I have replaced both output valves of the fuel pumps and the fuel pressure regulator but without succes.
I believe the problem must then be one of the fuel injectors leaking a little bit.
Is there a way to identify which of the injectors it might be?
I am assuming it is the W140 body... so 1992+ model year. You are right about the injectors are leaking. Take the spark plug out and see which one is most fouled up... that would the be cylinder where that injector is the problem.... too much fuel.
I had a very similar problem with my '97 E320. Perfect cold start but a bit of delay on hot starts - hot start within about 2 hours of shut down. I found stepping on the gas even a small amount allowed the motor to start more quickly.
The cause was a leaking (#6) injector. I found it by removing the spark plugs after the engine was cold. #6 was wet with fuel, the others were dry, as they should be. The motor was perfect after the one injector was replaced. Incidently, the problem started at only 18K miles when the car was three years old but was diagnosed and repaired at about 38K miles after ten years!
Yes it is W140 body (but year 1991.. they started one year earlier in Europe).
I waited until the morning. All plugs seemed dry and all with the same (little) amount of coating. I tried to see on piston tops too, and they were also dry. I tried to wait an hour while frequently spinning the fuel pumps (but without starting). Still all dry.
That would indicate, that injectors are OK. Or are there some other means to check it deeper?
Dr. Chino suggest wiring harness. Yes, they were bad some 2 years ago, and I replaced the bad sections of the wires (soldered and insulated with heat shrink tubes) at that time. Still there may be something, and I may have to look in that direction again.
When i starts (when problem is present), it chokes somewhat in the first 5-10 seconds or so, as if it has to get rid of the gas vapour, and then it runs fine. Also it starts well when stopped for only few hours. The problem occurs only when it has been stopped for several hours while sun shines on the hood.
So I lean more towards a fuel system problem.
To my knowledge, once the fuel pumps have build up pressure, there is only 3 ways, the pressure can escape: Output valves of the pumps (have been replaced), pressure regulator (has been replaced) and injectors. Plus, of course, leakage in the piping (no visible signs and no smell). Am I missing something here?
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