To diagnose a fuel pump issue, you should consult the owner's manual or a wiring diagram specific to your 1987 560SEL. A problem could be:
* A fuse in the main fuse box: This box is usually located under the hood, but the specific fuse related to the fuel pump circuit might not be explicitly labeled "fuel pump." You'll need the wiring diagram to identify the relevant fuse.
* A relay: The fuel pump is often controlled by a relay, which itself might be part of a larger relay panel. A faulty relay could prevent the pump from operating even if the fuses are good.
* A faulty fuel pump relay itself: This is a common point of failure.
* Wiring problems: Damaged wiring between the fuse/relay and the fuel pump.
* The fuel pump itself: The pump could simply be worn out.
In short: You need the wiring diagram to pinpoint the relevant fuses and relays. Without it, randomly checking fuses is unlikely to be successful. A repair manual specific to your vehicle is the best resource.
