Anybody out there know anything about the fuel pump relay's exact function? Does it have more than one posistion, does it control voltage at all, how does the engine act when it starts to go bad, or does it just puke and quit ? My Haynes manual doesn't discuss it at all! and only has a wiring diagram for Tpi. I,m working on an 88 form. Lo3, auto. Also getting a code 54. thanks

 

fuel pump relay is a on off relay. turn key on the ECM grounds the relay to cut the fuel pump on. relay could fail in the on or off position. it is howerver connected through the oil pump switch which could cause the relay to run all the time(key on or off) or not run at all.

 

Also, the oil pressure sw acts as a fail-safe. If the FP relay is shot, the computer will see oil pressure come up during cranking, then allows the FP to turn on, letting you get to the garage to R n' R the relay.

 

I've read if the fuel pump relay is not working you'll experience a longer starting period b/c you won't have fuel pressure until you crank the engine and oil pressure starts to build.

I also get the impression that the oil pressure switch may also affect the voltage being sent to the fuel pump.

Code 54 (less than 2 volts being seen by the fuel pump)