Fuel Pump does not shut off

[tnichols]

Can someone offer me any advise on fixing a problem I am having with my 1987 Pontiac Grand Am?

When I turn my car off, often you can still hear the fuel pump running. Then when I come out the next day to start the car, I find my battery is dead.

I replaced the Fuel Pump Relay, but it had no effect. Not sure what to check or replace next. Ignition Switch?

The car has about 180,000 miles on the odometer and is equiped with the 2.5 liter Ironduke 4 cylinder engine, with the automatic transmission.

Thanks,

Tom in Pennyslvania :( :???:

[Colin]

Since you replaced the relay , the ignition switch is the next likely culprit . It could be sticking in the on position , try disconnecting the connector at the switch and see if the pump shuts off .

[tnichols]

Hi Colin, Thanks for the information. Any idea where the ignition switch is located? Or how to get to it? The ignition switch might be the problem. When the pump won't stop, I just turn on and off the ignition (without starting the car) until the pump stops.

Tom...

[rixGAphx]

Originally posted by tnichols
Can someone offer me any advise on fixing a problem I am having with my 1987 Pontiac Grand Am? Disconnect the battery, leave the keys in the ignition, and abandon in a bad part of town??





:D :D

Like Colin said ^^^.

Temporarily, just diconnect the NEG (ground) battery cable each night.
PITA, I know.

A new ignition switch is about $40, and they frequently go bad.

[tnichols]

Originally posted by rixGAphx
Disconnect the battery, leave the keys in the ignition, and abandon in a bad part of town??



Very funny! I guess the car is getting a little old, but for the most part, it runs pretty good. I have added a Grand Prix to the fleet, but my Grand Am is the one with the trail hitch on it and I use it all the time.

I wonder if a bad ignition switch would shut everything else off and leave the fuel pump on?

[rixGAphx]

Originally posted by tnichols
I wonder if a bad ignition switch would shut everything else off and leave the fuel pump on? Yes.

The more-common problem with the GA is the fuel pump fails to work when all else does.

With a multitester you can do some cicuitry exploration and see what else might be 'on' (even if it's not doing anything).
But it seems to me you've eliminated the relay as the problem, and more importantly, your current 'disablement' method is continual farting with the ignition switch.

Since:
* this switch-fiddling apparently solves the problem, and
* the ignition switches frequently fail, and
* the car is 2 decades old, then:
Removing/checking/replacing this switch is the next logical step.

[ALMB~Nova]

i thought when the fuel pump reaches the desired line pressure, it shuts off. kinda like the pre start. or am i mis-understanding?

[HeyDace]

The PCM kicks the fuel pump on by grounding the relay for 2 seconds to prime the rail. When the PCM senses a start/run it grounds the relay full time.
What sounds like is happening is you have a short to ground in the circuit from the PCM to the relay...or the PCM quad driver for the relay is bad or short to battery voltage (switched voltage) after the relay to the pump.

...Kinda hard to diagnose over the internet though.

[rixGAphx]

Originally posted by ALMB~Nova
i thought when the fuel pump reaches the desired line pressure, it shuts off. kinda like the pre start. or am i mis-understanding? That's the way most diaphragm-type pumps work.
These are the type used in low-pressure applications for carburetors (5-8 psi, just enough to fill the float bowl).
British sports cars were equipped with these at the factory, and Mallory and Holley make them for aftermarket use on big american iron.

The vane-type pumps used on most modern fuel injected cars produce the high pressure (typically 30-45 psi for non-racing applications) necessary for the injectors to squirt enough fuel in a short time (milliseconds).
But they run (spin) continuously, and the excess fuel (not used by the injectors) goes back to the tank via the return line from the fuel rail.
The fuel pressure regulator is an automatic pressure-release valve at the return line. It keeps the pressure at the injectors high enough for operation, yet 'bleeds' off the excess pressure and volume into the return line.

[tnichols]

Yes, normally, I can hear the pump go on for about 2 seconds, after I turn the key on, but before I start the engine. After the engine is running, I can't hear anything except my noisey engine. People come up to me as ask "How I like my diesel?". I just tell them "fine". But it is a very noisey engine.

The fuel pump relay plugs into a 4 connector plug. So you are saying it is controled by grounding a wire? So I should test for gound, instead of positive? There is no schmetic on the relay. So I guess its either a short problem or the ignition switch.

Thanks,

[tnichols]

I pulled the fuel pump relay and the pump keeps on going. Where is this sucker getting power from? I took it to the shop and of course it does not stay running while there. So they could not find anything wrong with the car.

It only seems to do it after a 30 minute drive. Today on the way to work, it would not shut off. So I pulled the fuel pump relay and the fuel pump kept running.

[SE2000]

The ignition switch is behind the key. Not knowing that would indicate not a lot of tech. knowledge. So with that and the lack of oil pressure, you might want to buy a trailer hitch for one of your other cars.

[tenspeed]

Originally posted by tnichols
I pulled the fuel pump relay and the pump keeps on going. Where is this sucker getting power from?

Good question. Maybe you are checking the wrong relay. How about installing a toggle switch in the wire that feeds the pump? When you turn the car off, turn the switch off. Just make sure you find the right wire.

I had the same sort of thing on my '96 Achieva for the DRL's. They would turn on sometimes when the car was off. I was pulling the overload in the fuse panel but that was a hassle, so I put a fuse and switch in place of it.

[tnichols]

I am pretty sure I am pulling the right relay. When the car is working properly and you turn the key on, you can hear the fuel pump start up for about 3 seconds. With the relay pulled, you can not hear the fuel pump during that startup time. So it looks to me that the fuel pump power is comming from two sources. Either one can power the pump. I don't have a wiring diagram, so I don't know for sure.

Originally posted by tenspeed
Good question. Maybe you are checking the wrong relay. How about installing a toggle switch in the wire that feeds the pump? When you turn the car off, turn the switch off. Just make sure you find the right wire.

I had the same sort of thing on my '96 Achieva for the DRL's. They would turn on sometimes when the car was off. I was pulling the overload in the fuse panel but that was a hassle, so I put a fuse and switch in place of it.

[Rockfan1815]

now you do have a wiring diagram. Hope this helps.

It looks like the fuel pressure/ oil pressure switch would cause it to stay on. From the diagram it looks to be a normally open switch so maybe somehow it is closing when shutting the car off. I could be wrong though.

[tnichols]

Thank you! Thank you! Thank you!

I now it all makes sence. I think both my problems (fuel pump running/low oil pressure) might all be caused by a faulty fuel pump/oil pressure switch/sender.

Originally posted by Rockfan1815
now you do have a wiring diagram. Hope this helps.

It looks like the fuel pressure/ oil pressure switch would cause it to stay on. From the diagram it looks to be a normally open switch so maybe somehow it is closing when shutting the car off. I could be wrong though.

[HeyDace]

Originally posted by Rockfan1815
now you do have a wiring diagram. Hope this helps.

It looks like the fuel pressure/ oil pressure switch would cause it to stay on. From the diagram it looks to be a normally open switch so maybe somehow it is closing when shutting the car off. I could be wrong though.

May be sticking closed or there is an intermittent short to ground after the relay or OP switch.

[tnichols]

Problem fixed.. Actually two problems fixed... Both the low oil presure and the fuel pump not shutting off were both controled from the same oil pressure sender NAPA (OP6677)... $34.28 (inc tax) and a few hours work. Man, is it ever tight in there. Got my arm stuck for a few minutes. Though I was going to have to call the fire department. But the car lives on.

Thank you all for your help!:) :) :)