I've got a ground short to the connector pin that is supposed to turn the fuel pump relay on. Pin 85. No kidding. Anybody got a clue?

Recently replaced:
OVP
Crankshaft position sensor (CPS)

I can make the car run by jumpering the fuel pump directly. The fuel pump relay works.

Engine wiring harness anyone?

 

Correction to my previous post. No ground short, just using a schematic for an older vehicle. However the fuel pump relay is not getting a signal to run. I've traced the problem back to the ecu. It's not sending a signal to energize the relay. The car runs fine with the relay jumpered-no codes, nothing.

My next step is to replace the OVP again. After that I'll present it to my mechanic along with my credit card.

 

Always check your assumptions. I assumed the relay was working since it "Clicked" when I tested it. After checking everything possible I re-assembled everything....And IT STARTED. Tried it again and it wouldn't start. Turns out the relay was working intermittently.

This car does not have a fuel pump cut-off switch like the fords. Mercedes solved this problem by having the ecu monitor the MAF. If the car doesn't start within two seconds then the fuel pump relay is switched off. My mistake was assuming the relay was enabled when the key was on. The system was working correctly but the relay was intermittent.

Another clue was that the car was surging at idle for the few weeks leading up to the final failure. As I slowed to a stop the engine rpm would slow down and then pick back up. Very weird.

Thinking about it this is actually a better set-up than the inertial fuel cut-off switch on the Fords. If you have an accident in a ford the engine stops running immediately. In a mercedes you still might have a chance to control the vehicle after a collision. Just a tad bit safer.