I have Mercedes 500 SEL, 1985. Car has many repairs done . Now another problem where I need some advices. Recently the engine died while I was driving. Attempts to restart were unsuccessful. The fuel pump isn't working. However it runs if jumped from the battery. Fuel pump relay works too. I found something unusual: When I just connect the negative battery terminal, I heard a click of fuel pump relay (pump is not engaged by this), keys aren't in an ignition lock at this moment. Same can be observed when the fuel pump is connected to fuel pump relay by separate jump wires (I try to exclude the chance of short fuse in the fuel pump wiring). Can be this problem related to an ignition lock? Can somebody give any advice please?.