Hello, I recently picked up a 1986 Pontiac Firebird V6. The fuel pump didn't prime, and after replacing the pump as well as the filter and injectors, the fuel system worked. The car started and idled fine for about 2 days before it went dead. The fuel pump wouldn't prime, and there was no pressure. After much diagnosing, I replaced the fuel pump relay, but it didn't start right away. After a little bit of trying, the pump primed and the car started again. I swapped the new relay with the old relay, to determine whether that was the cause, but the pump still primed with the old relay. After a couple days of starting, I was driving down the road when it sputtered out and died. The fuel pump no longer primes and I had to tow it home. I am at a loss of what the issue could be, since it seems to have a mind of its own. Would love some advice or things to diagnose/test. Thanks!

 

It's possible that you have rust in your fuel tank and the inline fuel filter under the car is plugged.

This is the filter I used ,but there are other brands.

 

Accidental reply

 

Thank you for the response and pictures. Would this cause the fuel pump to randomly "go out" like its been doing? With the key turned to the "on" position, there isn't even 1psi of fuel pressure. I assume that even if the fuel filter was clogged, there would at least be a little bit of pressure?

 

When you turn your key on listen for the fuel pump to run. You may have to have someone else turn the key and place your ear next to the open gas cap.
If you can hear the pump start when the key is turned, you may have a plugged fuel filter.
If you don't hear anything when the key is first turned on, then you likely have an electrical issue.

 

the pump does not make any audible noise. This was the case previously, before it randomly started to work again. This is why it so confusing for me, as I can't seem to hunt down what's causing this issue. I've replaced the relay, checked fuses, replaced ECU, etc. Any diagnostics or tests I can try to help track down the issue?

 

Sounds like a loose wire or bad connection somewhere.

 

I agree with Aaron a loose wire or bad connection is the likely issue unless your fuel pump is intermittent.
This is the wiring diagram of your fuel pump circuit.

In this diagram it starts at the 20A inline fuse and can travel through two separate paths. On the car it has to go from the battery through the key switch first.
1 path goes through the fuel pump switch which is actually an oil pressure switch that closes on about 6 psi of oil pressure and the 2nd path goes through the fuel pump relay.

Method one would be to introduce 12 VDC at the oil pressure switch terminal A and see if the fuel pump starts? Yes and the problem is between the oil pressure switch and the battery, NO and a bad connection or fuel pump issue is happening.
The oil pressure switch is located at the oil filter and this picture shows the oil filter and cap removed from the oil pressure switch.



Method two
Start testing one path at a time when the fuel pump wont start, key on to see where you are losing the voltage.
One thing to remember is that the pump only runs for about 6 seconds when you turn the key to the on or run position and then the ECM drops it out because normally by then the engine is running and the oil pressure switch and ECM keeps it on. This is a safety feature so the fuel pump relay de-energizes if the main motor stops.

 

power, ground, and all the plugs inbetween the battery and the grounding bolt..
youll have to diagnose all of them.

I bet you have an issue with the wiring. To me, id run new wires and never look back..
rememeber these cars are getting old enough to where the wiring is going bad