i have a 1996 gmc sub
my wife was driving it up the driveway and it started spiting,sputting like it was running out
of gas. so i went to look at it when i did i trun the key on i could not hear the fuel pump
running so i took replaced fuelpump,fuel relay fuel filter,sending unit.wireing harness.
the fuel pump still will not run.
what else will cause the pump not to run?
The fuel pump test connector is a RED pigtail, single wire connector. It may be taped into the engine bay wiring harness. Find that connector an apply battery power. You should hear the fuel pump run.
Testing the fuel pump relay, you should find battery voltage (approximately 12 to 14 volts DC) in two of the relay sockets.
The fuel pump test connector is a RED pigtail, single wire connector. It may be taped into the engine bay wiring harness. Find that connector an apply battery power. You should hear the fuel pump run.
Testing the fuel pump relay, you should find battery voltage (approximately 12 to 14 volts DC) in two of the relay sockets.
Let us know.
i did as you said hook batt to red pig tail. i got nothing.
i just fuel pump out for 4th time hook it to batt it ran.
i did as you said hook batt to red pig tail. i got nothing.
i just fuel pump out for 4th time hook it to batt it ran.
If you applied power (with relay installed) but got nothing from the pump while installed, but did get the pump to run once removed, you should check the harness and connections from the tank forward. Close visual inspection of the relay sockets (in the fuse block) and all connector halves at the tank is crucial.
You could also check for power at the pigtail for voltage when ignition is turned on.
If able to get to fuel pump connector,
Look for voltage with ground as a reference, and then check for ground using a known good hot for reference.
This will tell if you are losing the hot or the ground. See if you get 12 volts to fuel pump connector.
You could also check for power at the pigtail for voltage when ignition is turned on.
If able to get to fuel pump connector,
Look for voltage with ground as a reference, and then check for ground using a known good hot for reference.
This will tell if you are losing the hot or the ground. See if you get 12 volts to fuel pump connector.
heres what i did. i checked volts at pump only getting about 8volts on one wire.
then i took where the wires come out from relay center check them nothing.
then i pulled relay out checked socket where relay pluged in at i got 12.45volts on one wire
others nothing. it act like the power is not coming out from under the hood and going to pump.
There won't be battery voltage at the RED pigtail with the ignition on. If there was already power there with the key on, why would that test connector require power to test the circuit?
The Vehicle Contorl Module (VCM) controls the relay (see the right side of the relay) thru terminals 85 and 86. The Orange wire in ternimal 87 is Hot at all times. When the key is turned to RUN or START, the relay coil energizes and then closes the switch, connecting 87 to 30 and feeds power from there to the fuel pump on the Grey wire. The relay has to be installed and it has to operate properly.
If you suspect the relay might be the fault, you can either substitute another relay into the fuel pump socket or if you can determine which terminals there are, with a suitable jumper, jump 87 directly to 30 (Orange to Grey).
If the pump doesn't run from either of these tests, trace the Grey wire until you find the open circuit.
Ah, I see, the way I would have added the pigtail, would be connect to A3 instead of B2, this way you could feed Power directly to fuel pump, AND could be used as a test point for testing(Relay energized, and Power Present).
Another thing I don't like about their drawing is, if ignition happened to be On, Feeding power to Jumper would not make it to fuel Pump. A Mechanic should know better, but the average person doing the test, might test with ignition On, Connecting to A3 would not have that Problem.
Linear Mode
