87bluebird

hi my car is currently an 87 firebird with a 2.8 v6 and auto trans with mpfi. bout 2 weeks ago i went to tops for groceries and when i was putting the grocerys in the car i heard something that sounded like an electric motor kick on in the back over the rear axle. the car had been off for like 20 mins and the only electric i know of in that location is the fuel pump. i just said wtf and ignored it it was only on for like 30 seconds and stopped. then bout a week ago i was cleaning out the back seat, the car had been off since the previous night. and i heard the pump kick on again. again i just ignored it last i got home and shut the car off i wasnt feeling to good so i sat there a min before i got out. after bout 2 mins of being off the fuel pump kicked on again this time it stayed on almost a minute. and i unpluged the car starter to see ifthat had a short and was turning it on but it didnt stop. what else could cause this? any help is greatly appreciated thank you

vetteoz

iTrader: (13)

Oil pressure switch that supplies power direct ( even with key off ) to fuel pump faulty maybe?
Next time it happens disconnect the OP switch and see if pump stops


http://austinthirdgen.org/mkportal/m...ine_wiring.gif

85irocinjected

Are you 100% sure its the fuel pump and not an electric hatch motor? If it is the fuel pump then its either ^^^what he said, your fuel pump switch is faulty or you have a short somewhere on the TAN/WHT wire to/from the pump itself.

The relay is just for priming the system, and the oil pressure switch takes over the power supply to the pump as long as there is pressure.

87bluebird

hatch motor is ripped apart and wires cut to it. so it aint that and were are those 2 switches located so i can test them? i sat in the car for 40 mins todays while waiting to see some one and pump came on 3 times staying on longer each time.

85irocinjected

Back of the block by the distributor.

ZZ3 Z28

I would suspect the oil pressure switch, too. However, shouldn't that fuel pump relay cut power off if the key is not in run position?

Upon further review, now I'm second guessing myself. After looking at my shop manual, when the key is in run, the fuel pump relay activates for 1.5 to 2 seconds to prime the injectors, then turns off. When it receives the references pulses from the distributor the relay activates the fuel pump again. If no ref pulses are received the ECM deactivates the relay shutting down power to the fuel pump.

So how is power getting to the fuel pump if the relay is supposed to cut off power when no ref pulses are being received? Could the relay be bad? Stuck?

87bluebird

what does it look like? anyone got any pics i will try to find it tomorrow morning

vetteoz

iTrader: (13)

Elementry
As I noted above and can be seen in the circuit diagram I linked ( which is why people put links up ! )
the power supply from the OP switch is DIRECT to the pump;
it doesn't go anywhere near the relay
when OP switch is closed ; pump will run unless you disconnect battery

Typical GM Pump circuit

87bluebird

yes i have looked at that link a hundred times today am i blind or is the oil switch not on there? and i think i have an idea were it is but not positive. also just got thinking thats the same part i need to replace cuz i switched from idiot lights to full gauge dash.and it dont send right signal to run gauge could the gauge be messing it up? the gauge dash has been in since i think october tho?

Maverick H1L

iTrader: (8)

These guys have V8's and don't seem to know about the V6...

The OPS is on the oil filter adaptor, the 2-wire one. The other one is for the gauge or switch (you still have a switch for your idiot light cluster which is why the gauge isn't working... LMK if you want my old one, that I should still have if I haven't chucked it, because I don't need it).

Unplug your fuel pump relay first. I'll bet it's dead and is shorting internally (and it's easier to get at with the engine hot). And then check the wires in the connector underneath it to make sure they're not shorting together (insulation melts or some crap and comes off, leaving bare wiring).

vetteoz

iTrader: (13)

87bluebird

yeah i aint too far from leroy pm if you find it and how do ik which relay goes to fuel?


and vetteoz ok i was looking for oil something switch in that diagram.lol

vetteoz

iTrader: (13)

Switch is only operated by oil pressure ,
it is part of fuel pump circuit so in this case you would start at the fuel pump and follow wiring back until you found it.

Maverick H1L

iTrader: (8)

They won't call it the oil pressure switch... That would be for the dash.

It's the fuel pump switch, and, like I said before, it's the 2-wire unit on the oil filter adaptor.

The fuel pump relay should be the one in the middle next to the brake booster (coolant fan on one side and the A/C compressor clutch relay on the other), has fat orange wire and a green wire and a tan wire (tan being the output).

87bluebird

will have to go by the wires cuz i doubt there still in the right spot i replaced the wiring harness and all the relays a year or 2 ago. and i am gonna finally do oil antifreeze and stuff like that in a min. and will look at the wires on the reallys to see if i can find it