1997 Pontiac Sunfire fuel injector problems

Car was running fine, then developed a small leak from the o-ring on the #3 cylinder fuel injector. Replaced it with a new o-ring, put it back together, and turned the key to activate the fuel pump, and there was no leaks. When we tried to start the car however, the engine turned over only about 1/4 turn and then locked up. Thinking it mightve thrown a rod or something similar, we pulled all 4 spark plugs, which came out fine. So we spun the engine over with a rachet only to be greeted with 4 cylinders full to the top with gas emptying themselves out the spark plug holes. We disconnected the battery and kept spinning the engine over with the rachet, the cylinders kept filling back up until it had pumped probably close to 2 gallons of gas out the engine. We cleaned up all the gas and reconnected the battery, and primed the fuel pump again, only to have it do the same thing. However, if I disconnect the battery right after priming the pump, it still fills each cylinder back up 4-5+ times. Im stumped here since I could understand maybe installing the #3 injector back on wrong and filling up that particular cylinder, but its filling up all 4, and the other 3 injectors werent even touched. I did some research and found out that leaky injectors are a common problem on this car, but everyone else seemed to only have 1 injector filling up the cylinder, not all 4 filling up all 4 cylinders. Their fixes also seem to be hit-and-miss, sometimes new o-rings fix the problem, somtimes a new injector, and I even read of having to go through several brand new injectors before the problem stopped. With injectors at 200$ apiece, replacing all 4 several times is not an option. Any suggestions??

You need to look at the fuel pressure regulator. If the regulator diaphram has a leak, each time you run the fuel pump it’s going to fill the cylinders with gasoline.


I ran across a BMW that was towed in from another shop,injectors constantly on. It turned out the previous mechanic pinched the F.I. loom between the head and valve cover after doing a valve adjustment (yes it was in valve adjustment days)

Thanks guys, Ill take a look at both things tomorrow. Is there any way all 4 injectors could get stuck open, even with the battery disconnected, and having only touched one?

I agree with the fuel pressure regulator diagnosis.
If this turns out not to be the case another possibililty could something wrong with the electronics causing the ECM to maintain a constant ground on the injectors whenever the key is in the run position.

A constant ground would keep the injector pintles retracted all of the time and this would allow a constant spray of gasoline.

When you get this problem resolved you must change the oil and filter. Gasoline diluted engine oil is very hard on crankshaft bearings, piston rings, etc.

A constant ground/ECM fault makes sense but this is happening with the battery disconnected. That part is whats really got me stumped.

And yes, we do have a new filter and case of oil waiting.

I think we will pick up a new set of o-rings tomorrow just to eliminate that. Is there any gaskets or o-rings on the regulator that we need when we remove it to check it?

. . . . . . . . . . . . . .FUEL INJECTORS FLOODING ENGINE
The fuel injectors’ ground-side wires are being inadvertently grounded before they get to the engine computer (PCM), or, they are being grounded inside the PCM at the wrong time. This accidental grounding turns the fuel injectors ON, and keeps them ON (spraying fuel) as long the battery is connected, and will really flood the engine.
The short to ground has to be found and repaired. To check the wires for grounding: Disconnect the battery, and disconnect the PCM electrical connector(s). Use a digital multimeter to check the pins on the PCM, through the PCM. If any PCM F.I. pin to ground shows very low ohms, that’s a problem within the PCM. The PCM will, then, have to repaired, or replaced.
Check the wires from the PCM connector to the fuel injectors for grounding. If any are grounding, visually examine the wiring from the fuel injectors to the PCM for damage, and shorting, to ground.
Here is the wiring diagrams: Fig.7 http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?chapterTitle=Wiring+Diagrams&partName=Chassis+Electrical&pageId=0900c1528003cfdd&partId=0900c1528003cf0b
Enlarge the image, and enlarge again. Use your pc View, and go to Zoom In 6 times. If you can’t go to the page, you may have to register at www.autozone.com. to get in.

Your question on fuel flow after the battery is disconnected: When electrical power is removed from the fuel pump, the fuel pressure is still in the lines. The fuel pressure is there until it bleeds off through an internally leaking fuel pressure regulator, leaking fuel injectors, or fuel pump. O’ring seals will do nothing for this problem.

You don’t need to remove the regulator to check it. Just remove the vacuum hose from the regulator, and if gas leaks out of this connection the regulator is leaking and requires replacement.


Well we ended up taking the #3 injector back off, and it turns out the lower o-ring somehow disappered between taking it off and reinstalling it. Bought another o-ring kit and put it all back together again, changed the oil, and it fired right up and runs great. Thanks again for all the help!!

That’s great that the engine flooding (and from your description, what a flood!) has stopped. You may have, inadvertently, done something which shorted the fuel injector wires to ground. Anyway, if the flooding happens again, let us know.