I have an E39 530 DSE with a starting prob and its become very expensive now having had a new crank sensor ,new cam sensor and a new fuel pump the fuel pump being the one under the near side seat, the car will not start sometimes no matter what you try , go back a few hours later and there is a good chance it will run like there was nothing wrong.
the last thing to be replaced was the fuel pump and all seemed well for 2 weeks , got in the car this morning and once again the same damn problem is back ,there was a light frost this morning and I noted that no pre heater warning showed up, although it very rarely does, is this a clue !.when the engin is running it is perfect with no miss fires or lack of power.
I spoke to a BMW technician and was told that even without the pre heater circuit running the car should start with a little effort . is this true ! could it be a fuel pump relay , if so where will I find it,or could it be the lift pump in the tank.Any help would be so appreciated. Chris