No voltage to fuel pump?

[GN138]

I am in the process of moving and do not have my GM manuals. I think I've checked every fuse and they are all good. What would cause there to be no voltage at the fuel pump? This is with the stock wiring.....

Car has been driving awesome. Last Thursday I went to start it, let it warm up and just before I went to drive to work it died and won't start.

Also, I have a hotwire setup I got from Caspers but the stock exhaust melted a part of it when it rusted and came loose, so I have been using the stock wiring. Anyone have the instructions for the hotwire setup?

Thanks,

 

[GN138]

Actually, we have 8 volts to the stock FP wiring at the gas tank. We have 12 volts going to the hotwire relay at the gas tank but no voltage coming out of the relay. Still doesn't explain why the stock wiring won't work? I have a Walbro 340 that is loud and I can't hear it running/ priming at all. Is 8 volts not enough?

 

[salvageV6]

Is the 8 volts with or without the hot wire relay attached to the circuit while you are measuring it?

If it's on the stock wiring alone without the relay hooked up most likely it's not enough and not providing enough current to lock the hot wire relay on providing voltage out to the pump.

I'd look at the factory fuel pump relay first you should be at 11-12 volts out of it on the gray wire at the relay, key on test and the voltage will only last 2 seconds if the car isn't running or cranking and building fuel pressure assuming the factory wiring is still in place on the oil pressure switch.

 

[GN138]

I haven't been using the hotwire for awhile because it got messed up...so, let's stick to the stock fuel system.

I tested voltage at the back of the car and it was 8 volts, but I think I had the key on for awhile. I don't hear the FP running at all. I even depressed the schrader valve to release what fuel pressure was in there and it wasn't much. After that, the pump didn't run.

I'll have to go out and see if the voltage is different when I have the voltmeter hooked up and then turn the key on.

Where is the stock FP relay?

Thanks!!

 

[GN138]

Ok, so, with the key off there is no voltage to the FP. When I turn the key on, the voltmeter goes to 7 volts for a milisec and then right to 8 volts.

We found the FP relay but how do we test?

Does this sound like I need to replace the relay?

Thanks,

 

[GN138]

Ok, 12 volts going to the relay and we're only getting 8 at the fuel pump. Is it the relay?

I checked for the infamous hanging brown wire by the driver's side header and it's not grounded out.

 

[Sal Lubrano]

I am not sure about this but I think the low oil pressure sender has something to do with power getting to the fuel pump. Might be worth checking out. Good luck.

 

[ESP Products]

The brown wire is actually Gray, regardless. The wire to the oil pressure switch is there to keep the fuel pump running as long as there is oil pressure. A safeguard while the engine is running. If you have 12 volts into the relay and 8 volt right out of the relay, then it may be the relay. It's cheap enough to change it out and at least have a spare. More than likely you have corrosion in your 12 volt wire to the pump. Best solution is a hot wire kit, they are about $35 +/-. Remember your harness 20+ years old.

Hope this helps you.

 

[FastTurb]

HI check the connector in the trunk of the car, driver side deep in the back corner. very possibly either the ground or the hot lead (or both) is making a poor connection through the plastic connector. I've jumpered around the connector with solid wire soldered in. good luck

 

[vicious6]

Do not mean to hi-jack this thread but I am having some of the same problems here. My car also has a Hotwire kit (that I did not install), a very noisy Walbro 340 and no more than about 8 volts to the factory three wire plug at the back of the car. If I unhook the Hotwire kit (the wire from the alt.), my pump will not come on with only the factory wiring hooked up. I just replaced the pump and it is new. While I had it out I checked all the connections on the sender for continuity and the all checked good. What is even more strange is the fact that I drove the car the other day after installing the new pump and all. Car runs good until you tip into the throttle and it starts sputtering before any amount of boost comes in. I have a fuel rail gauge on the car. It reads approx. 35 lbs when the pump primes before it cranks, only about 20 when the car is running with the line on.

Any ideas?