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ase_master327, Shop Owner
Category: Chevy
Satisfied Customers: 5288
Experience:  +15 years experience with Chevrolet. Bumper to bumper diagnosis & repair.
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88 chevy: wiring harness..under hood..fuel pump..relay and fues is ok

Resolved Question:

i have a 88 chevy 1500 with 64-67 327 I changed the wiring harness( it had many wires cut) under hood and in the dash, when i installed the used harness the fuel pump isnt working( installed a new one and relay and fues is ok (it doesent seem to be getting power to it) what else can i check or do to solve this problem
Submitted: 8 years ago.
Category: Chevy
Customer: replied 8 years ago.

1988 Chevrolet 1500 64-67 327

Already Tried:
replaced wiring harness under hood and dash( orginaly woulnt start no power to starter also replaced starter switch and nutural safety switch and will start when i put gas in engine fuel pump worked b/4 wiring harness went on now doesnt work (put a new pump on and checked it so i know it works) seems to be wiring problem again also put new relay on and fues is good what else can i check.. it has aprox 7.5 volts going into the fuel pump plug
Expert:  ase_master327 replied 8 years ago.


Hello, and thank you for choosing Just Answer!


With 7.5 DCV, you might look for loose connections or a low battery.. Loose connections get hot.


The easiest way I know to help you is to show you the wiring diagram for it. and you can go from there. Because with wires cut, and yu changing the harness and all... there is just no telling what all you got going on in there.


If you know the pump is not getting power, then here is the diagram:



Another thing... If the engine is now carbureted, you will need to install a fuel pressure regulator on the system, because the carburetor is only designed to have 7PSI fuel pressure, and the pump puts out close to 2 times that, and could cause problems with the float...


ase_master327 and other Chevy Specialists are ready to help you
Customer: replied 8 years ago.
hi. it has a fuel presswre regulator on the system should the fuel pump be getting 12v and can this electric pump be wired with a switch directly safetly also all the cut wiring has been replaced and all works except fuel pump, should I unhook harness at fire wall and rehook it maybe some of the stock sealer has gotten between the conection??? also the battery is new but seems to be defected I had a charger hooked to it and charging at the time i checked it
Expert:  ase_master327 replied 8 years ago.


I gave you the wiring diagram of the system.. Just find out where the 12 volts drops to 7 volts, and you have found the problem.