tempermental E30 fuel pump

[bmtrblu]

Having trouble with a 1988 325iC, all stock. Cannot get it to start. No signal to fuel pump. I have spark, but no signal to run fuel pump. Replaced: crankshaft position sensor, fuel pump relay, DME relay, Ignition harness, main engine ground, swapped ECU with same result. I can jump the Fuel relay and make the fuel pump run, but cannot start. When fuel pump is jumped and running, it is moving fuel. Any ideas???

[AwakenNoMore]

I had a short in my fuel pump connector on my car when I got it. Same symptoms. Never hurts to check.

[jlevie]

If the pump will run and rail pressure is normal with the relay jumpered, the problem would seem to be that the relay isn't engaging. Check to see if power is present at the relay coil when the ignition is switched on. Then check to see if the DME grounds the coil when the engine is cranking/running. One, or perhaps both, of those will be missing.

Since the DME has been changed with no change, the cause of a missing coil power/ground will probably be the engine harness.

[bmtrblu]

I'm going to start with the harness this holiday week. Any ideas how to tackle this, where to start, etc?
I'm guessing I will start by peeling back the outer insulation and start following everything along. From there...?

[vpilarrt]

I'm guessing I will start by peeling back the outer insulation and start following everything along.

Before you do that check to see if any of the wires are bad by checking the resistance with a volt-ohm meter from one end to the other. You may have to use a jumper wire for the long runs (like the connector at the pump to the relay).

[mpowerful]

Also check obc code relay under drivers dash. Check power to coil. If no power check back through c101 then under dash to ignition switch. Check fuel pressure. The fuel pump relay is switched by the main relay. Just stream of thought things to check hahaha.