fuel pump

[pete380]

I have an 85 380sl that starts and immediately shuts off. I know the fule pump is ok (jumped pins 7&8) and I replaced the fuel pump relay. I believe there is still a wiring problem to the relay. What keeps the relay engaged? Any ideas what to check? Thanks

[whunter]

You need to know.

The initial "starting" fuel pump power is 10 seconds.

Then the signal from the crankshaft position sensor -

which passes through the OVP (Over Voltage Protection relay) -

going to the fuel pump relay = telling it the engine is running.

If it does not see this signal = no power to the fuel pump.

Mercedes-Benz Driveability
Evaluating Electronic Engine Controls
by Steve Brotherton, Import Specialist
Published in: ImportCar∞, February 2001

OVP relay, Over Voltage Protection Links
OVP relay, Over Voltage Protection Links - PeachParts Mercedes ShopForum


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[pete380]

My tach has stopped working at the same time. Is there any connecton between the two problems? Thanks for your help

[abiby]

Originally Posted by pete380

My tach has stopped working at the same time. Is there any connecton between the two problems? Thanks for your help

IIRC, the tach signal is also what tells the fuel pump relay that the engine is running and that it should continue to pump fuel. ergo... no signal, no fuel.