elvis1985

i have recently bought a 1982 pontiac firebird (knight rider replica) with the 305 engine (5.o liter engine on crossfire injection) but i am having trouble with the injectors. i cant seem to get any fuel to spray out of the injectors into the engine. We have replaced the fuel pump and filter, checked the fuses and had a test light on the electrical connectors on the injectors (which flashes when trying to start car). we are a little stuck on what else it could be and i dont really know much about these sort of cars. thanks for your help.

bakes85

maybe the injectors them selves are bad

transam85dudeman

oil pressure sensor. replace it or check for shorts in the wire leading to it. It prevents the fuel pump from pumping with/o a signal of good oil pressure. tune your tps afterwards and time the engine. since this is youre first car with 80's technology, i advise you to pick a manual 20 bucks at autozone. its a 100% worth it. AND it has the wiring diagrams that everybody kills for

elvis1985

ok thanks guys, i give them ago and hopefully it will work. tried all the other stuff

ploegi

No it doesn't. The oil pressure sensor is backup power in the event of relay failure. That's it. It is NOT a low pressure shutdown safety thing. Never has been.

Gumby

The oil switch will kill the engine if you drop below 7psi

The switch doesn't turn on till you reach 7psi also.

Why on mine the relay is not used.

It may take a crank or two to get enough oil psi to trip the switch, but the pump doens't start until it reaches 7psi, which is a good thing, having oil psi before an engine fires. Why mine is clocking over 220,000 miles and still runs strong. Cold start up is hard on parts, unless you build oil psi first.

ploegi

I disagree. If you look at the wiring diagram, (as it comes stock from the factory......) The oil pressure switch is connected to supply side, AFTER the relay. It cannot break the circuit. Only supply power.

Gumby

If the switch can turn on and power my FP and it only works when you have oil psi, then no oil psi means no power to FP......

It would defi logic though I have never lost oil PSI while running to test.

I suggest you try it to prove your point.

ploegi

Look at the wiring diagram. Circuit 340 (12v going TO the OPS).

Circuit 120 Gray wire, power TO the fuel pump, fed FROM the relay.

Wire from pin C on the OPS goes to a junction in circuit 120. The grey wire can get power from the relay, OR the OPS. (or both....)

I would also point out, that if the fuel pump couldn't run without at least 7 PSI oil pressure, it wouldn't prime when you first turned the key on either.

The OPS is backup power for the Fuel Pump. That's it. For a test, find an unmodified car, and unplug the OPS. The car will start right up, and run just fine. Plug the OPS back in, and unplug the relay. The car will crank until oil pressure comes up, and then start and run fine. Unplug both, and it won't start at all.

Now, unless you can show me a wiring diagram that gives the OPS the ability to BREAK the fuel pump circuit...... I stand by my assessment.

Gumby

I was just commenting on that it does act like a switch, cause my relay system has never work, my pump will not prime when I turn the key on. I must crank it over up to 3 times when really cold out to get enough oil psi to trip that switch. Then my pump primes and it fires.

Now I did replace relays and junk but it has never worked.
Then I didn't care as its a good idea to build oil psi before you start.

But its whats turns my pump on, so it should be able to turn it off but have no plans to test that.

ploegi

You are correct. If the relay is NOT supplying power, (failed relay) when your oil pressure drops YOUR engine (with a FP relay that doesn't do its job...) will quit. (well, at least very shortly after pressure drops, there will be some residual pressure in the lines...) But, in the stock configuration, with everything working as it should, even if oil pressure goes to zero, the relay will STILL be providing power to the fuel pump, and you will smoke your motor. The ECM doesn't care about oil pressure at all, as long as it sees the engine turning, it will send power to the fuel pump via the relay.