I have a 1991 Mercedes 190E (gasoline, not diesel), and while it's still a reliable car, it has a strange problem with starting the engine that left most people I asked puzzled (including mechanics), so I'm posting the situation here hoping that someone might have experienced something similar.
If I try to start the engine after not using the car for at least a day, or if I start it up within a few minutes of stopping it (e.g. dropping a friend off or waiting for a train to pass), it's all fine.
However, if I try to start it within a a few hours (but less than a day) of stopping it (typical scenario: leaving it in a parking lot when going shopping, to the cinema etc.), I hear the starter "buzzing" and all, but the engine fails to start up. It usually takes many-many tries, to actually get it started. I've found that it helps if I step on the accelerator pedal while turning the ignition key, but even then it takes a few minutes (and a few key-turns) to get it running. While it never actually left me in the parking lot, I'm very afraid of this scenario so I'm using it less and less for shopping. I've tried taking it to a mechanic of course, but they haven't found anything.
Has anyone experienced or heard of anything similar? If so, what was the solution?
It might be worth noting that while the battery has been replaced quite recently, so it should be reliable, we routinely use a nonstandard "master switch" to cut the car's circuit from it, to make sure it doesn't drain unexpectedly. I don't know if this is relevant to the issue.
(Sorry for my limited mechanical vocabulary, I rarely talk / write or even read about cars honestly.)