Question about 1991 Chevrolet C1500

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1991 chey pick up 1500 electric fuel pump

The wiring harness for the fuel pump has three wires to it, how many wires should show voltage when the key is in the on position

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Hello, Only 2 wires show be hot when fuel pump power is supplied. I think that the gray wire is the power side so ck that wire to ground. Also, fuel pump power is supplied from your oil pressure switch and the fuel pump relay only supplies power for a few seconds until the truck is started. Keep in mind that the fuel pump will only run a few seconds by just turning the switch on. If you want the pump to stay on without the motor running , you will have to by-pass the fuel pump relay.
I hope this will help.
CYA, gator241

Posted on Feb 06, 2009

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The ignition module and the pick-up coil/stator located inside of the distributor is what generates the signal that the ECM (Engine Control Module) uses to time and fire the fuel injectors, as well as the signal to run the fuel pump and the dwell signal to fire the ignition coil, and a faulty ignition module can cause any one or all of these systems to malfunction.

There is also the possibility that the ignition coil is faulty and first check to see if full battery voltage is getting to the "Pos" (+) positive side of the ignition coil when the key is in the "Run" position, and also that full battery voltage is getting through the "Pos" (+) or positive side of the ignition coil and over to the distributor and ignition module, dis-connect the wire connector from the ignition coil to the ignition module and if battery voltage is not present at the connector to the ignition module with the key in the "Run" position but it is present at the "Pos" side of the ignition coil, then the ignition coil is faulty.

That does sound like a malfunction with the ignition module inside of the distributor, and you can remove the ignition module and have it tested for free at most auto part stores. If the ignition module does test out alright then the problem could still be in the pick-up coil/stator, (it can be tested using an ohm meter by dis-connecting the wire connector from the pick-up coil/stator and the ohm reading between the two wires from the pick-up coil/stator should be between 500 and 1500 ohm's, and both of the wires from the pick-up coil/stator should show an open loop or an infinite reading between each wire and ground) and if the pick-up coil/stator is found to be faulty then replace the entire distributor, or the distributor will have to be dis-assembled to install a new pick-up coil/stator.

If you do purchase a new ignition module be sure that it does come with a silicone grease or a die-electric compound because it is a heat sink and the ignition module will burn up without it.

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Put new fuel pump now the pump runs but the power wire only has 7 volts of power how much is it suppose to have


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How do you check voltage on the fuel pump on a 2001 Chevy Silverado, was driving engine stalled but regained power drove three more miles and it quit running, I have spark but no fuel. Trying to check out...


Hello Dennis.
When you are checking fuel pump voltage on your pickup when you turn on the key the voltage is only applied to the pump for a couple of seconds unless you go to cranking position.
There are 4 wires leading to the fuel pump on your truck. The gray wire is the 12 volt positive power feed to the fuel pump and the black provides the ground. The orange and purple wires are your fuel gauge wires.
The relay for the fuel pump is in your under hood fuse panel and I believe is marked on the underside of the fuse panel cover. It should click on and off again quickly when you turn the key to "on". Having a helper to cycle the key would be handy while you put your finger on the relay and listen to it. Just because it clicks still doesn't mean it's functional but relay failure on these models is somewhat rare.
I would start by checking for power at the fuel pump harness.
Fuel pump issues are quite common on these model year trucks.
Hope this helps you out.

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