i recently installed a new fuel pump, it worked, then i had to replace the tumbler and starter, the car sat for about a month and after i did that i cranked over the motor but no fuel pressure, all fuses good, fuel pump relay is new, but not getting any power, ran 12v straight to pump and pump kicked on. pulled the computer out. and written on the computer is 1990 caprice 5.7 chp car. i have a 88 iroc. i checked the orange wire all the way back to the computer and no volts there....im assuming that this is the bad computer or does power come from a different leg of the harness?

 

Orange wire at pump relay doesn't go to the computer
The computer operates the relay which supplies power on the orange wire from the batt through the relay
to the pump
In any case the stock oil pressure switch will ( should ) run the pump as soon as you crank the engine over
( your OP switch is working isn't it ? ) .This a backup to run the pump should the relay fail.
So if it the pump doesn't run when engine is cranked likely you have blown the fuse on the feed wire which
supplies both the relay and the OP switch

Should have 12V on the org wire at relay ( and OP switch ) all the time with the key off

 

Does you car have the VATS key? (the key with the black
pellet on the shank)

If it does and you installed a incorrect key/ignition cylinder
the anti-theft system activates and shuts off the electric fuel
pump.

Just a thought......................

 

my orange wire doesnt have voltage on or off, no power at all to that orange wire to the relay. and i dont believe it was, but i cant remember off hand, the old key is still stuck in the old tumbler

 

VATS shuts off the injectors and starter only; fuel pump will continue to work

 

Start here
https://www.thirdgen.org/forums/elec...e-problem.html
https://www.thirdgen.org/forums/elec...line-fuse.html
https://www.thirdgen.org/forums/elec...t-battery.html

If you replace the inline fuse and it keeps blowing
Read

https://www.thirdgen.org/forums/elec...eeds-help.html

 

awesome!! ill check all that tomarrow

 

ok quick question, just to be 100% i did find a fuse behind my fender that was blown, replaced it and had power to my fuel relay, but still nothing to the pump, took the connection off my oil pressure switch and jumped it and bam, fuel pump on, even with key on off position, so bad OP sensor right?

 

You know the pump only runs through the relay for 2 sec when the key is turned on , then relay shuts off until
the engine is cranked over?

Switch not sensor
OP switch should close and power the pump with cranking oil pressure (4 psi + )
Disconnect the relay , crank engine over ,pump should run. If it doesn't consider the OP switch faulty.