560SEL Fuel Pump Operations
 

Hey everyone,

I have a quick question, my buddy has a 560SEL.

When you turn the key, normally (on my m103 & m116) you hear the fuel pump kick on and then off in short order.

On his m117 the fuel pump kicks on and continues to run. Is this normal operation?

Or is something wrong, if so any ideas as to what?

Problem solved.

PO ran a wire from the engine bay direct to the fuel pumps themselves.

Looks like one of them went bad and took out part of the connection to the fuel pump relay (all melted) and he decided to bypass it.

Your PO isn't as clever as he thinks.... Doing that causes a couple of things; firstly, the high RPM fuel cut-out is now bypassed, making it possible to rev above redline. Secondly, it puts more wear on the pumps.

If you hadn't discovered that little hack, my first guess would have been that your fuel accumulator was shot and your fuel system was never getting fully up to pressure.

I'd happy to report that once we repaired the damaged, the pumps operated as they normally should and the car started fine. Aside from some vacuum leaks and subsequent stalling issues.

Presumably, he didnt realize he toasted the fuel pump relay's one pin (i believe it was pin 6 (30-opens for one second to prime system))..and just wired them to the ignition.