bruce lamoureux

iTrader: (1)

I have a 1991 firebird with a tbi carb thing .the car stopped running ok I moved it to the garage .started by dropping the gas tank because I didn't here the pump kick on , so before I put everything back together I plugged the harness from the tank into the plug above the rear end and turned the key to run and couldnt hear the pump kick on so I unplugged it turned the switch to run and checked it with a meter and nothing on the gray wire . ok then I went up to the battery and checked the fuse there ,then the relay on firewall , then checked the fuse block under drivers side dash every checked out good ,so I thought it was the ECM put new one in and moved the prom to the new one also ,and still nothing at the pump . I even changed the oil switch thing above the filter . what am I missing?

redneckjoe

gonna have to keep tracing the wire down.
http://austinthirdgen.org/mkportal/m...ine_wiring.gif

Drew

iTrader: (58)

There's a short test pigtail coming off the fuel pump relay, by the brake booster on the firewall. I want to say it's a red wire. If you run a jumper wire from that red wire to the positive battery terminal, the pump should run. If it doesn't, the wiring, pump, sending unit, or relay could be bad. If it runs, you might still have a faulty relay, or a problem with the wiring upstream of the relay. But doing that simple test bypasses about half of the system, eliminating a pile of possibilities.

tealman92

Swap the relay with the fan relay and see if you get power. If you do then replace the relay

bruce lamoureux

iTrader: (1)

I have replaced the fuel pump relay and I have 12v there, and have 12v at the fuse under the dash . where does the gray wire come from that goes back to the fuel pump?

redneckjoe

the gray wire comes from the oil pressure switch and the relay. the relay will have 12 volts on the red or orange, but you need power to the gray obviously. the relay gets turned on by the ignition switch. i doubt you have a short, or it would blow a fuse? gonna have to keep probing the wire. i' start at the back, fuel pump connector, connection behind rear seats, then i think it runs under the drivers door sill?

bruce lamoureux

iTrader: (1)

the orange wire at the relay has 12v so I should have 12v oil pressure switch . so I need 12v coming from the ignition switch to give me power to my gray wire at the relay ?

redneckjoe

watch this video around 45 seconds. the guy gives some clear explanations of how the fuelpump circuit works with diagrams.

in a pinch, or as possibly anti-theft, you could run a power wire with fuse, to a toggle switch, then to the gray wire at pump. (oh man, i'm gonna catch flak for this one, lol.)

bruce lamoureux

iTrader: (1)

thank for the video , I have replaced the oil pressure switch , so I need to check if I have power to the wires going to the switch

bruce lamoureux

iTrader: (1)

could someone point me in the right direction to get a wirring diagram of a1991 firebird formula .all the ones I find have different relay wiring colors ,they don't match my car.

Tuned Performance

iTrader: (92)

http://chevythunder.com/1228746_ecm_198992_tbi.htm
http://www.austinthirdgen.org/index.php?pid=19
http://www.gearhead-efi.com/Fuel-Inj...Information-61

bruce lamoureux

iTrader: (1)

thanks for the info.it will help ,happy new year!!!!!

BigBlockNBK

I was trying to run the fuel pump to empty it of bad gas and it worked for a little while but then I lost the power at the fuel pump relay, no blown fuses. I then went straight to the battery and that worked for a couple times then stopped. I dont think Im empty yet though.

BigBlockNBK

Found it, there is a fuse under the hood next to the battery

Tuned Performance

iTrader: (92)

Correct that also powers the ecm