90 grand am le 2.5 stalls

mavisky · #1 09-28-2003, 07:17 PM

i have a 1991 grand am le with the 2.5 in it and 41,000 original miles. today as i was driving to my dad's house it just cut out on me. after calling him to come and get me and waiting around 10 minutes or so it started right back up again. we made it about 4 miles or so when it did it again. stalled, sat for 10 minutes then started right back up again. it did it one more time before we finally got it back home. we already put a can of dry gas in the tank since i had just filled it up the other night but that was after it stalled for the second time. obviously that wasn't the problem as it stalled again on the way home.

i'm thinking that its the fuel pump relay or the ecu, or possibly the fuel pump itself. while it was running you could hear a faint whine from the fuel pump (i'd already pulled the rear seat to see if i could access it w/o dropping the entire fuel tank). i also noticed that if i shut the car off on my own instead of it stalling, when restarting it i could hear it prime the fuel line with the pump quickly when i turned the key to the "ON" position. when the car had stalled and i tried to restart it i never once got the fuel pump to prime. this leads me to believe that the relay might be at fault. of course the starter will engage and the engine will crank over all day long but it won't fire.

on the other hand i noticed that my engine temps were slightly higher than normal and that as soon as i let off the gas and got on the brakes for a corner i could clearly notice the water temp dropping.

i know the air filter is a little dirty but that shouldn't be it. i just replaced the alternator and battery and the car is fully topped off with oil. i'm about certain its one of 4 things. either the fuel pump itself, the fuel pump relay, the engine computer, or the ignition coil (i don't think it uses a distributor since the spark plug wires run underneath the intake manifold).

i'm interested to see what you guys have to say about this and i'd appreciate the help in at least finding out how to get to the ecu or the fuel pump relay since those are the only two items i can't easily trace down since i can't seem to find the haynes manual anywhere.

mavisky · #2 09-28-2003, 09:53 PM

anybody here??

seriously how many people are on this forum?? i'm used to forums of 10,000+, guess this one isn't that big.

GMMerlin · #3 09-29-2003, 06:30 AM

First thing we have to do is determine what is missing...fuel or spark.
When the car cuts off again, pull off a plug wire and spin over the engine..do you see or hear spark jumping?
Next pull off the air cleaner and watch the injector when you spin the engine over...does gas spray out of the injector?
Determining what is missing will help lead you to the root cause of the problem before you spend money on parts to try and fix it.

mavisky · #4 09-29-2003, 09:37 AM

i keep forgetting that on this car i can actually see the fuel. only had it a month. the annoying part though is that i have to go drive it around until it stalls before i can repeat the problem. otherwise as soon as i hit the key it just starts plain as day.

mavisky · #5 10-11-2003, 06:26 PM

okay big day for the P.O.S. went out and picked up a new fuel pump relay which proved to be useless. after the car stalls there is no fuel whatsoever to the fuel injector. i can't tell if the fuel injector just isn't spraying when the key is turned to start or if its trying to but there's no fuel in the lines. seems more like the first than the second. we pulled the relay out of the harness and checked for power. we had power to 86 and 30 and a good ground on 87, but when we turned the car to on (after it had stalled out) we weren't getting any signal to either of the other two terminals 85 and 87a. i might have 87 and 87a confused right now though, but regardless its acting like it doesn't want to prime the fuel pump and of course it won't start.

any help would be appreciated as the car will probably be taken to a shop after this as the only problems i can think of would be in the wiring harness itself of possibly the ecu.

Trixcomp · #6 10-15-2003, 10:25 PM

hmmm, do u have any error codes u can read. yeah it sounds like a computer problem. or some sort of electrical device between the ecu and the fuel pump relay. ecu replacement would probally cover the most ground. but u could consider tracing wires and such. Sometimes. heat, or vibrations can disengage broken wires causeing power failure. you could check yoru service manual for wire diagrams. good luck to u.

GMMerlin · #7 10-16-2003, 06:18 AM

Jumper the pink/black wire to the gray wire with a 10 amp fused jumper. If the engine starts and stays running, than you have eliminated the fuel pump or the ECM.
Look at the oil pressure switch. It controls the fuel pump after the 2 second prime from the ECM and while the engine is running.

RABarrett · #8 10-16-2003, 09:24 AM

I don't know where some people get their information. The fuel pump runs from two sources, the oil pressure switch and the fuel pump relay, driven by the ECM. If one fails, the other should not permit the engine to starve for fuel since, when the engine is running, it should have oil pressure. It should also have an rpm signal that the ECM uses to operate the pump. That would require two problems to starve the engine for fuel. I suspect the ignition module, which controls the spark. I have seen these units fail frequently enough to advise replacement, but again, not without a thorough check out. These units are expensive, and if you push the tech, he will guess, for which he cannot be held responsible. There are several other possible sources for the dying, all of which require checking out before replacement. Ray

GMMerlin · #9 10-16-2003, 01:27 PM

I don't know where some people get their information.

Quote:

Originally Posted by GMMerlin

Jumper the pink/black wire to the gray wire with a 10 amp fused jumper. If the engine starts and stays running, than you have eliminated the fuel pump or the ECM.
Look at the oil pressure switch. It controls the fuel pump after the 2 second prime from the ECM and while the engine is running.

You are right about that...it doesn't even make sense to me and I wrote it.

Lets back up a little bit and start over.
With the key on, you should have 12v on the pink/blk wire at the relay. If you remove the relay and jumper the pink/blk wire to the gray wire with a 10 amp fused jumper you should hear the pump run.
When the engine wont start, remove the connector at the top of the injector. Using a test light, carefully probe between the to wire terminals and have someone spin the engine over...the light should blink.
At the same time remove 1 plug wire from a plug and lay it close to the engine as you can...when the engine spins over does spark jump out of the boot?

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