BluFBdy

iTrader: (1)

This just started happening out of nowhere, and its random when i drive my car for more than 5 mins and shut it off my fuel pump will run constantly until it kills my battery (yeah found that out the hard way) Im used to the pump priming momentarily when i shut it off so i just walked away and didnt think about it but now its an issue, ive been just pulling the FP fuse, its not worrying me too terribly much because Ive got a 350 TPI and a T56 waiting to drop in the car but in the mean time its still my DD....and id still like to know wtf is going on lol

any ideas?

Carlos773

iTrader: (3)

Relay maybe?

Zepher

iTrader: (1)

stuck relay, bad ECM, or the oil pressure switch is stuck, I am leaning towards the oil pressure switch.

To isolate either one (if your car doesn't have the pressure sender and switch in one, which is a 3 wire unit above the oil filter), you can unplug the fuel pump relay, start the car and drive and then turn the car off and see if the pump continues to run.

Unplug the oil pressure switch and just run on the relay if the pump continued to run using the above method.

Just had a thought, you could have dirt in the oil pressure adapter causing pressure to stay in the switch when the car is turned off.

BluFBdy

iTrader: (1)

I'm thinkin its the opsu also

camaronewbie

Behind the battery, tucked in the fenderwell, there is a fuse in a weatherpack - remove that fuse. This is the power connection for the OPSU fuel/pump circuit - if the car still starts, runs, etc with that fuse out, then you know the OPSU is bad.

It 'thinks' it senses oil pressure when there is none - same thing happned to me years ago. The OPSU is about $40 these days - but you can just leave the fuse out - won't affect anything UNLESS the fuel pump relay goes bad, then you'll need to replace that fuse in order for the pump to run until you can get a new relay.

wrenchmonkey

Without the oil pressure sending unit, the pump will only prime for a few seconds at key on.

Really the easiest way to tell if it's the OPSU, is to unplug the OPSU while the pump is running (engine off), and see if the pump turns off.

If it turns off, replace the sending unit.

If it doesn't turn off, take a look at the fuel pump relay. It may be stuck. if all else fails, it might be the ECM, but that would be my last guess.

Zepher

iTrader: (1)

It's not the OPSU. That is the sender for the gauge oil pressure.
It is an oil pressure switch.

I see OPSU used in many posts when they are referring to the switch, which will confuse people when they go to the parts store to buy a replacement.

BluFBdy

iTrader: (1)

Ill give that a shot thannks guys

wrenchmonkey

Good point Zepher. I used a switch out of a Blazer, which combines the two into a single unit... I guess I assumed it was the same for F-bodies as well.

BluFBdy

iTrader: (1)

Looks like a relay I can't get the damn thing off though its like superglued on I've got a spare somewhere I just gotta find it

Zepher

iTrader: (1)

It is for the later models, can't remember when the changeover was made though.

BluFBdy

iTrader: (1)

I believe I've got the changed over version

wrenchmonkey

2 wires, or 3?

BluFBdy

iTrader: (1)

3

wrenchmonkey

So did the relay fix it?

BluFBdy

iTrader: (1)

Unfortunately no, I unplugged the relay while it was priming, with no luck so I reached down and pulled the oil pressure connector and it stopped, its out of whack so I bought a new one, haven't installed it cuz I've got a 350 waitin to go in and its gonna end up on there in a few days anyway so I don't wanna mess with it, ill just keep pulling the fuse and call it my ghetto anti theft lol all the accdessories and sensors that can swap over wiill be moved everything from that sensor to the starter is goin on , yay for budget builds lol