JaNusSolSumnus

I was trying to cycle my fuel pump to clean the lines out in preperation for fuel filter replacement and pump replacement. However I couldnt get the pump to cycle for one reason or another.

I have the ECU and all internal wiring hooked up. the only variable is I removed the motor and anything that would connect to it is just hanging out. Is it possible that the chassis needs to see the fuel sensor in the secondary rail before it will actuate the pump?

Thanks,
~Kris

mad_7tist

no. if the pump is not running when you jump the diag box you have a dead /disconnected battery, blown fuse etc..

JaNusSolSumnus

Well the battery connection was loose but I tightened it and was getting adequate power inside the car. This was with a fully charged 51R 'yellowtop'. What possible fuses could be blown? I checked the ones under the hood but saw nothing popped.

The two methods I tried to run the pump were, once just priming it with the key ON and then another with the key ON and using a jumper wire in the fuel pump relay socket. Neither seemed to be sending power to the pump, I had someone with their ear to the pump and it was silent. I removed the access panel and varified that the pump was indeed connected still. Not really sure what I should check next.

Thanks,
~Kris

saxyman990

Did you try jumping the FP to GND terminals in the diagnostics box (with the ignition "ON")? That's the FSM method for jumping/priming the fuel pump.

JaNusSolSumnus

Nope, which pins in the diag box are for the FP and GND?

~Kris

saxyman990

The ones labeled F/P and GND

If you no longer have the cover on your diagnostics box to show you which pin is which, then look on page F-96 of your FSM. It'll show you exactly which terminals to jump.

-Rob

JaNusSolSumnus

I couldnt remember if it had a sticker on the cover or not so I guess that answers that. If not I have the 94' FSM in PDF form on my PC.

Thanks,
~Kris

TailHappy

I just went through something similar. Fuel pump wasn't starting up on key on.

According to the wiring diagrams, you SHOULD be able to jumper F/P and GND and the fuel pump should start up, bypassing the fuel pressure resistor, even if the ECU isn't connected. However, that wasn't the case for me. No matter what I tried, I couldn't get the fuel pump to start up using the jumper. Ultimately I replaced the PFC, and then it would start up with the key on, and the diagnostic box would also cause it to run continuously. So the key switch and the ECU can cause your pump not to work.

Also to check are the fuses under the hood, but also the ones under the dash. I had one blown under the dash (engine, I think). Then there's a circuit relay under the hood that can cause your pump not to work. There's another relay that bypasses the fuel pressure resistor, but that one shouldn't matter since you'll get current regardless of it's state.

There's a good drawing of the system in the FSM. It's a surprisingly simple system.