89 firebird formula 5.7 TPI automatic

can a faulty oil switch (sending unit) what ever you want to call it cause a fuel pump not to prime. im getting code 54 my car will normally start up with a hard crank in the morning (no pump priming) it just takes a minute and you can watch the oil pressure rise and it will start up and run fine after that. once turned off some times it will start back up by doing the samething and sometimes it wont start and wont build pressure im completely lost on what else it could be and dont think it could be the oil switch but was wondering if someone on here knows a little more here is a list of the parts replaced alrady

fuel filter
fuel pump
gas cap
fuel injectors
cap
rotor
plugs
wires
MAF
cleaned IAC
ICM
ECM (used old PROM)
fuel pump relay (multiply)

The inline and fuses under dash are all good. and i can use a wire to jump the poer at the relay and pump wire witch will shoot the fuel pressure right up to 47 PSI and the car will turn right over (does not hold pressure you have to turn it over fairly quickl) no fuel prssure jus cranking the key except when the car will start first thing in the morning like stated above. i have also used a noid light on the ECM wire at the fuel relay and when you turn the key to on position it turn the light on for about to sec. so its wanting to ingauge the pump. and the ground at the relay is good or else the power wire at relay wouldnt beable to engauge the pump at the relay.

Any one have an idea what im missing or maybe had a similar problem i tryed to go into as much detail as possable i took it to a local shop just to pay them 50 bucks for the guy to tell me to just run a toggle switch into the car so i didnt have to pay them what he estimated at around 500 dollars before he thought he could find the problem.

thanks for any help

 

To answer your first question, A bad oil pressure switch should not prevent your pump from priming. The signal from the oil pressure switch is not used for the prime. If the switch was failed open, you could start but not run. If failed closed, your fuel pump would continuously run with the ignition in ON even if the engine was not running.

You say you've changed the relay (a couple times) with no joy, but you can jump the power from the hot wire to the pump power line and get it to work. I would check the ground from the pump relay connector. Without a ground the relay will never close with the signal from the ECM because it can't complete the circuit. On my 91, the ground is BLK/WHT but I know they change them all the time. My other wire colors are ORN - PWR from fuse, GRY - PWR line to pump motor, GRN/WHT - signal from ECM, and RED - Pump prime connector.

 

ok thanks you dont happen to know where it grounds on your car do you

do you know what the 3 are that run to the pump, of course the blck is ground but them their is a pink and a tan oneand do you happen to know where they run i cant find them on my wire scymatic

i believe the tan runs to oil switch and pink to ECM which would mean the pink sould only run for 2 sec when first turn key to on position. my gets constant power when key on and very dim light on the noid light (you would almost mistake it for not coming on if not looking very closely)

 

The Tan should be the sending unit for fuel level. My power wire is Grey. The sending unit is a big varible resitor so the output will depend on the fuel level.

According to the service manual, the ground for the fuel pump is under the driver's seat on the floor rail. The ground for the pump relay is driver side rear of the engine compartment (Near the relay itself). Your pump ground is good or the pump would never run so I would focus on the pump relay ground circuit.

 

Sent you an email.

 

Cn you re send it I don't think I got or or might have accedently deleted it thanks

 

Found it thanks I'll email you back ASAP

 

thanks to Zig we managed to find out the guy before wired the fuel pump connectors wrong so car is fixed and going to be legal next week i hope
thanks everyone for the help

 

Glad I could help. If we could just get the hackers to stop mutilating the wiring harnesses, we would all have a few less headaches...