Question about 1989 Pontiac 6000
Hi- I have a 1989 Pontiac 6000 LE station wagon with a 2.8L V6 with multi port fuel injection. Recently the car died while driving. When I attempt to restart, the engine starts, but instantly dies. Every once in awhile I can get it to run very roughly for a few seconds and then it dies.
There was a trouble code stored (code 45 for rich exhaust) but it's possible it could have been stored a long time ago, long before this current problem.
Eventually I started doing basic troubleshooting for spark and fuel delivery. A spark tester indicated that I had good spark on all cylinders and so I started looking at fuel issues. I connected a fuel pressure gauge to the Schraeder valve on the fuel rail and turned the ignition on to energize the fuel pump. The pressure went right up to proper specs (46 psi), but as soon as the pump stopped running after the 2 second period that ignition on energizes it for, the pressure rapidly dropped down to about 24 psi.
I have a factory shop manual with troubleshooting trees that explains how you can isolate the problem by connecting some special fuel line adapters with shut-offs to the pressure and return lines. I was able to obtain these and did some further testing. In the first step, you energize the fuel pump and then shut off the pressure line before the pressure has a chance to drop. If the pressure then holds, the manual says that this is an indication of a bad check valve in the fuel pump or a leaking coupling hose or pulsator at the fuel pump. If the pressure still doesn't hold the manual indicates that you either have a leaking injector or fuel pressure regulator and tells you a further test to do shutting off the return line to isolate which of those two issues is causing the problem.
When I did the first test (shutting off the pressure line after energizing the pump) the pressure held so this appeared to indicate that my problem was with the pump or it's coupling hose and not with an injector or the fuel pressure regulator. I don't believe that this system has a pulsator.
So I was basically all set to pull the fuel tank and check these things out, but as this is a fairly big job (I've dropped it before for other problems and this time I'd just filled it up with gas to make it even more of a hassle), I started going over in my mind again exactly what the troubleshooting I had done was telling me as I didn't want to drop the tank if the fuel pump wasn't actually the problem.
I started questioning this because although I lose pressure when the pump isn't running, when it is running the pressure is up to specs so I would think that the car should run OK. If the check valve or some other internal leak is causing the pressure to drop only when the fuel pump is not running then this would seem to cause hard starting or increased starting times, but not keep the engine from running OK as long as the fuel pump was running.
To further diagnose things I tried to see if I could get the engine running even briefly to check the fuel pressure while running. I was able to do this once for maybe 5-10 seconds, albeit very roughly, before it died again. The pressure held at just over 40 psi as long as it was running. As soon as the engine stopped, it dropped down again to 24 psi. I can hear what I assume is the fuel pump relay making a click at the exact same time that the pressure begins to drop. This always happens whenever I do the pressure test by just energizing the fuel pump with the engine off as well.
So at any rate, I'm a little hesitant to drop the fuel tank at this point. Shutting off the fuel pressure line appears to hold pressure which is supposedly telling me that I definitely have a problem with or in the vicinity of the fuel pump, but it doesn't seem like it should cause the car to basically not run. There are no signs of any external leakage in the pressure lines anywhere from the fuel tank to the engine including the fuel filter. The fact that the pressure pretty much holds after turning the shut-off closed on the pressure line also supposedly eliminates a leaking fuel injector or pressure regulator as well, so I'm in a bit of a quandry as to what to do next and as I mentioned, a bit hesitant to drop the fuel tank if the problem turns out to be elsewhere even though my tests seem to indicate a fuel pump issue.
I might also mention that to further eliminate the likelihood of a leaking fuel injector, I pulled all six spark plugs, energizing the fuel pump a few times prior to pulling each one and didn't seem to find any sign of raw fuel on the plugs. I also pulled the vacuum hose off the pressure regulator to check for fuel. Apparently there would likely be fuel in that line if the regulator diaphragm were leaking. Again no sign of fuel. But again, I did this testing just as a backup as the fuel rail held pressure when I shutoff the pressure line with the fitting on the adapter hose immediately after pressurizing the system and before the pressure started to drop.
Any advice that you could give me on this issue would be greatly appreciated.
WoW...There is an intelligent person out there!!! Most posts say "My car...its broke" Looks like you have really done some comprehensive testing. As you observed though, The problem you revealed may have more in common with a delay in starting. My first thought is that though you have pressure etc. Have you tested the fuel for contamination? Water (from condensation etc) can give you similar problems.You mentioned that you just filled the tank I wonder with what? Also how good is the spark, and is it firing when it should? Though I'm inclined to think less of that idea.
Posted on Jun 18, 2009
Does your engine have an oil pressure switch? Sometimes these go bad. It is a sending unit which sends a signal to the ECM to allow the fuel pump to remain on. It is for both engine protection and safety in the event of a crash.
However, when the sender goes bad, the pressure built in the initial cranking, which is around 2 seconds when you turn the key on is used up quickly. The engine starts but then immediately dies when the pressure goes away and the ECM thinks there is no oil pressure. Try replacing the sender or bypassing it by consulting an electrical schematic.
Posted on Aug 21, 2009
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Posted on Jan 02, 2017
Hello this is a feature to stop the engine and exhaust system from filling up with gas when spark is lost! years ago fuel would be delivered as usual and you Eng and converter would be full of gas real hazard back then!!!!now they built into computer when spark fails fuel automatically shuts off safety feature??? or not? so i would start to test coil this is a good place to start and if you have engine light on plug in OBD 2 scan tool to retreve the fault hope this helps you out and if you do not have a proper spark tester tool i would invest in one most auto parts stores usually carry them!!! $15-$30 dollars usually.John
Posted on Feb 15, 2009
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