So wife went to drive the car today and it wouldn't start. CEL came on and I'm getting code 54... "Fuel Pump Circuit Low Voltage". Wheres the fuel pump relay on a 91 305 TPI? I found this thread https://www.thirdgen.org/forums/v6/1...code-54-a.html but its for a 2.8. Is that the same? I'm assuming it's different because the wiring doesn't match

For ***** and giggle I tried swapping the one that he mentions is the fuel pump relay (left most by the break booster) with the one beside it, but that didn't solve the issue either. The wiring he mentions (Tan/white, black/white, green/white,) doesn't match any of the three relays.

When I turn the key to on without starting, I don't hear the fuel pump.. So I'm guessing its either the pump or the relay? Anything else it could be?

 

So I tested the relay itself, jumped the fuel pump and it turned on, jumped the back up oil pump it turned on, checked power at green white when key turns on, it has 12 volts….


Only thing I haven’t done is check pressure at fuel rails. Have to find my fuel pressure gauge. But figured if pump is running, only reason it wouldn’t have pressure at rails is if it’s leaking. And if it’s it’s leaking I’d likely notice that.

Anything else I’m missing?

 

Engine running what’s the voltage at E13 of the ecm ?

 

Engine was running fine with a bit of a hard start. But since CEL came on it hasn’t.

it has nearly 12 volts at the green white wire and then dropped after a few seconds which if I understand correctly, is what supposed to happen. I think it was 11.7 volts highest on the voltmeter.

I have a fuel pressure gauge coming today to test that.

 

So fwiw, I tested fuel pressure today and it seemed fine pre start up and fine at idle. Put it all back together and it started up fine and drove well. Code is gone.

Not sure what the issue was. Going to keep an eye on it and see if it reappears. Might be some mild corrosion or something on a connection somewhere.

Thanks for replying.

 

Problem solved ? If it happens again might check fp feedback voltage at ecm if low look for a splice in the harness near the ops. It could have corrosion.

 

Yeah hasn't happened since putting it all back together.. Everything looked clean so We'll see if it reappears.

 

Sometimes it’s a poor connection so pulling things apart and putting back together can solve issues.