Anyone have a wiring diagram for the fuel pump? I just got this truck is a 91 with a 5.7 and it has a bunch of wiring issues.. first the pump is not getting power. Relay is good and when I put power to the pump it turns on... Is there a inline fuse that I am missing? I also cannot find any "fuel pump fuse" im just lost in the sauce... any help will be appreciated..
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
Fuel Issues
- Thread starter Slim220
- Start date
JPOutfitters
1/2 ton status
check the ground from the tank to the frame..........where are you supplying power directly to the pump? Are you powering from the test wire under the hood on the firewall?
I did not know there was a test wire under the hood...where is it?! lolI am running a wire from the (+) erminal to a lil section in the middle of the truck along the frame rail... Btw its only my second chevy my firs was a pos 91 s-10 with the 2.5 in it.
JPOutfitters
1/2 ton status
JPOutfitters
1/2 ton status
See the female connector hanging down from the black box? Make a jumper wire to go to the + battery terminal.........and then check if the pump is pumping!
JPOutfitters
1/2 ton status
I believe there's a relay under that cover.......
Dude you are the man!!! I was wondering what that was for.. I have had it for 2 weeks now and have been going through a bunch of wiring problems.. I only paid $550 with a freshened 5.7 with like 20 miles on it 
JPOutfitters
1/2 ton status
Just a good starting point!! When my fuel pump went out a couple years ago it would pump but not at enough fuel pressure.....a fellow offroader showed me that and we were able to test the pressure by removing the fuel filter and putting in a gauge that he had.
JPOutfitters
1/2 ton status
then you my friend are having the same problem I was.........the pump isn't pumping enough pressure! Time to replace that pump in the tank!!!! Remove the fuel filter at the frame rail and use that test wire to pump what fuel you can into some fuel cans to empty it. Then drop the tank and replace that pump.
You may have just popped the pump off the line in the tank........cross your fingers!!! It could be running and pumping right back into the tank. Otherwise you just replace the pump.........the pump isn't that expensive in it's self.
You may have just popped the pump off the line in the tank........cross your fingers!!! It could be running and pumping right back into the tank. Otherwise you just replace the pump.........the pump isn't that expensive in it's self.
JPOutfitters
1/2 ton status
make sure you blow off the top of the tank really good with some air or high pressure water before you remove that ring........you don't want dirt falling into the tank!
JPOutfitters
1/2 ton status
that test wire just bypasses the relay.......you may have a bad relay!
No "inline" fuses I know of,there is one in the fuse box for the fuel pump though--but I've seen about 100 EFI trucks that had corroded plugs and connectors at the fuel pump ,or the wires turned gangrene long the length of the frame somewhere,delivering only a few volts,instead of the full twelve needed for proper fuel pump performance..most new pumps come with new plugs for the power wires and most of the time the whole wire should be replaced..its a common dilema o GM's..
Chances are your pump is dying too though,usually just fixing the wiring dont help,its already too late--low voltage ruins pump mptors and the pumps usually are tired when they have close too or over 100K miles on them...
Chances are your pump is dying too though,usually just fixing the wiring dont help,its already too late--low voltage ruins pump mptors and the pumps usually are tired when they have close too or over 100K miles on them...
If you are turning the key to 'ON' and then crawling under the truck to check for voltage, you won't find any. Why? Cause when you turn the key to 'ON' power is fed to the pump for 3 seconds and then stopped. Unless there is a crank signal from the ignition module there will be no more voltage fed to the pump. This is to prevent the pump from running constantly while the engine is off.
Have someone in the truck turn the key to on while you are under to check for voltage. Or use a test light and hang the light where you can see it while reaching in the truck to turn the key. It should light up for like 3 seconds or so and then turn off. If it does, you are getting voltage back there. Now crank the engine and make sure the light comes on while cranking.
Have someone in the truck turn the key to on while you are under to check for voltage. Or use a test light and hang the light where you can see it while reaching in the truck to turn the key. It should light up for like 3 seconds or so and then turn off. If it does, you are getting voltage back there. Now crank the engine and make sure the light comes on while cranking.
JPOutfitters
1/2 ton status
I'm telling you that you need a new pump..........
I'm telling you that you need a new pump..........
x2
but, he's insisting that there is no voltage back there. I was just trying to make sure he's looking at the right time.
JPOutfitters
1/2 ton status
I thought I showed him there is voltage to the pump by showing him the test wire under the hood!
