Hi guys, some good info for sure! The wiring scenario is a definite possibility in as much as the loom on this engine is most definitely cooked, (I would love to replace it) I have repaired/replaced a fair number of wires on this. I wish MB had a connector kit for these so I could build a new loom. I have found nothing online but one could hope some day☺️. Frank I think your possibility #1 is a good possibility. I have opened the fuel pump relay and the boards look to be in good shape, though without any method to test it I cannot be certain. Stretch as far as I can tell I have no VSS I do have a crank position sensor I cannot recall where the fuel pump relay gets the signal for the auto trans. kickdown perhaps from the CPS. I did get into startekinfo.com really fantastic. I may finally figure out where a wire that was lying in the fenderwell belongs (its a brown with blue stripe wire with a single pin connector) none of the cheesy aftermarket manuals have been of any help. Thanks guys I will look harder at the wiring. I will wiggle the wires while it's running a little harder maybe I can get it to fail on demand.

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Ken

1984 190E project 1 soon to be daily driver.
1993 300E project 2 waiting on engine rebuild

Where would we be without these wonderful projects...

The FPR gets a "run" signal from the ignition controller (EZL). It also inhibits kickdown above a certain RPM to prevent overspeed.

A partial test of the FPR can be done by removing it and bridging circuits #30 and #87 (typically pins 7 & 8) in the socket. The pump will run continuously in this configuration, and the car can be driven to see if the symptom changes. Remember to remove the jumper when thru with the test!!