my fuel pump quit running i changed relays and nothing happend so i pulled the relay and hooked it up too a switched 12v source. i was trying to drain the carb to rejet it and i pulled the power wire out of the weather pack connector. it stayed running for a long time so i looked at my pressure guage and found it still had 5psi. the pump doesent prime when i put the key on but it seems to come on as soon as the engine kicks over. the ecu has been pulled out and i pulled both of the relays on the drivers side by the brake booster. does the oil pressure sensor kick on the fuel pump even with the relays pulled?

i drained the carb a few weeks ago and when i pulled the power wire the pump shut off so im not really sure whats going on. i dont wanna be driving around and have the engine die on me cause the fuel pump decides to turn off.

91 firebird originally a 305 tbi now a 350 carb with stock pump.

could it be vats related?

 

Yes! The fuel pump will run with the key in your pocket.

Here's the deal:

2 power sources for the fuel pump,

1) power from relay, fed from battery by signal from ECM - this powers the priming of the pump, and ECM signals on/off

2) power from the Oil Pressure Sending Unit (OPSU) - this continuously powers the pump - a direct supply from battery to OPSU to pump.

A bad OPSU can send direct current to the pump, regardless of anything else (except disconnect of battery). My 1992 carbed Camaro did this - took me weeks to trace it - drained my battery every 3-5 days - finally late one night I walked past and heard the pump running, but key was in the house.

If you removed the ECM, you should not have a priming of the pump anymore (I don't). However, I've also found (one time only) that my pump wouldn't run at all without jumping wires on the relay connector directly (orange and brown I believe) - but again this was only once, and after the car sat some weeks without running.

Anyway, try a new OPSU, about $30.

 

I'm having the same issue except my car started bogging down after I heard this. I can't drive at all. The car is running so poorly. I heard the fuel pump on late one night as I was taking out the trash. Car worked fine the next day. But the day after it felt like there was a severe spark issue or fuel issue because of the bogging. Now today the car will hardly idle. Guessing fuel pump going bad?

 

Bad fuel pump doesn't usually give any warning, it just goes. When mine went bad, I was on the highway, 2 hours out of town. Was cruising along, car stumbled, and died. Got it restarted, and got another 5 miles to gas station, where it never revived.

It's possible that the constant drain on the battery has weakened your battery - try charging it. Also, try another battery before starting a fuel pump swap. A constant battery drain like that can kill a battery.

Try anything else before a fuel pump swap! Make sure your relays and OPSU are functioning correctly, you have a fresh battery, you have continuity on all spark plug wires, and spark on each.

 

I believe the battery is fine. It's a few months old. The wires have been changed within a few months. I don't think it's the pump because I just went and started the car and it runs fine til it goes closed. When it's closed it ideas around 500-600 very poorly and then it would return to open loop and run ok for 5-10 seconds at about 1500 then go back to closed and run poorly. So what does that mean?

 

Oh, well open loop/closed loop is a whole new story. I wouldn't have a clue - I yanked all that crap out and went carb.

Start searching/asking about loop stuff.

 

so the relay is only for priming the pump and the ops is the constant power once the engine is running?

the only way i can keep my car running is to put power directly to the brown wire on the relay. its the wire in the middle on the bottom. thats not going to hurt my pump is it?

 

As best as I've been able to tell.

Straight wiring should not hurt the pump - as long as it isn't running all day and night - you'll need to remove the jumper while parked, overnight, etc until you get the problem resolved, or get it jumped to a run-in-hot only wire where it won't get juice unless the key is on.