I admit, having grown up on carburetters, (or were they carburetors?) I’m a little lost on fuel injection systems.
This pickup was towed to me yesterday, dead as a mackrel. It had been sitting for about a year after the owner gave up trying to make it run. I tried to charge the expensive Optima battery. It would not take a charge, so I replaced it. When I tried to start it, it would run for a moment and die repeatedly. I thought it might be out of gas although the gauge said it was full. About a quart later I figured out the gauge was right. So I grabbed my fuel pressure tester, only to find that the pin in the center of the connector that is supposed to depress the valve core in the Schrader valve was missing. No problem, I just removed the valve core from the fitting and screwed the knurled fitting on. I turned the key and got a substantial reading of 58 PSIg. I let some fuel out of the pressure tester, and checked it a second time. Sure enough 58 PSIg again. So I tried to start the engine. It started right up, and continued to run at Idle for several minutes. I put the core back into the valve, and started it again. Since is was pushing 7:00, and I still had another project to finish up, I left the truck until this morning. Just like yesterday, it would start and run for half a second or so repeatedly. I tried simply depressing the Shrader valve core to see if purging a little air was the answer, but it made no difference. I did not press it for long as I didn’t want a big mess. The tester has a hose to drain fuel into a cup. So I removed the Schrader valve core and hooked up the fuel pressure tester and went through the same drill as yesterday. It started right up, and idled for several minutes. So I got gutsy and drove it four miles around the section. It ran perfectly. It has been sitting for an hour, and I just started it again. I know it’s not fixed, as I’m sure it will not start in the morning. I can’t very well send it home with my fuel pressure tester.
I do not see any leaks anywhere, or smell fuel except when I vent it on purpose. The engine is a 5.7L Vortec V-8. The truck is an early 2000 model, produced in July of '99. It looks more like a '99. Apparently there were some changes in both engine and body that year.
Do any of you have any ideas as to why it is acting this way? Leprechauns and demonic possession have been largely ruled out.
When in doubt try sea fome or heet, could be the gas is bad after a year. Though not recommended I have gotten engines to continue running with starter fluid in my holster, starts to die, hit it with fluid, keep it running and after 20 minutes and multiple shots of ether maybe the gremlins go away.
Of course drain the gas change the filter and try fresh gas would be another alternative
Key piece of info: its been sitting a year. Drop the gas tank and empty it out thoroughly. Check for rust, varnish, etc. The new ethanol gasses are really bad after sitting. Fresh gas should fix your problem Id say.
Except for three things, I would agree.
It quit starting when the gas was still fresh a year ago.
Once I got it to run, it ran well. No pinging or roughness.
The gas smells fine.
Of course there is also the fact that it has a 34 gallon tank. There’s over $100 worth of gas in there. I’d hate to condemn the gas without being sure.
don’t worry about the $100 gas. eliminate that as a possibility.
you can always reuse that gas in something else or even put it back in after you chase the gremlins
It started up perfectly this morning. I think I’ll drive it for a couple of days and see if maybe it just had air in the system from sitting around too long. Can that happen?
The owner said he already replaced the fuel and air filters when it wouldn’t start.
I still think you’ve got a fuel pressure problem. It’s just that in the process of measuring it, you change something, and that temporarily fixes the problem. My guess is the fuel pump check valve is on the fritz and allowing fuel from the fuel rail to leak back into the tank. If you do what you do to get it running perfectly, then leave the pressure gauge attached and turn the engine off, does the pressure remain steady through the night?
One other thing that is easy to check, most fuel injection systems have a fuel pressure regulator, usually on the end of the fuel rail. There’s a vacuum hose connected to the regulator. Remove that hose, does any fuel come out or is the inside of the hose wet with fuel? If so the fuel pressure regulator diaphragm has sprung a leak.
Edit: One other thing, since that pressure testing port is defective (since you have to remove the valve core), have you tried replacing it with a new one?
I’ve driven it about 100 miles now, and it has not failed to start and run well, even in the morning chill. I’m beginning to think that the fuel rail was full of air or bad gas which I purged with the pressure tester, almost by accident. Does that make any sense?
The tester port was not defective. It’s my tester that’s defective.
It doesn’t make sense to me
I think you’ve been lucky the past few days
I agree with George. it sounds like you’ve got an (intermittent) fuel pressure problem
To see if the fuel is leaking back into the tank due to a bad check valve you could leave the pressure gauge hooked up and monitor the pressure in the line while the vehicle is parked for the night. Along with a possible fuel issue the trouble could be with the ignition. It almost sounds like something is shutting down the fuel delivery system. The trouble could be electrically related, in the ignition system possibly. Whenever you suspect a fuel problem an easy way to see if that is true is to spray a small amount of starter fluid into the air intake. If the motor fires up you know what area to check, along with if it still doesn’t fire up.
You have pretty well proven the old gas is still okay. If the fuel filter hasn’t been changed already I suggest you do that. If the trouble shows up again make sure the pump is getting power to it. You wouldn’t want to replace the pump and then find out the real trouble is due to a faulty pump relay or something like that. Keep us posted on this MG.
Sorry I didn’t update earlier. I know we all like it when OPs update us.
The truck continues to run well, but it has had a couple of glitches that needed to be figured out. The new battery continued to run down over night. I discovered that the button on the door that actuated the door locks was sticking in the lock position, sometimes. That apparently continued to feed 12 volts to the door lock actuator. I hit it with some silicone spray lube. The truck has been fine since, except that the owner has to remove a fuse that makes the a beeper beep, or the battery will run down too. The continual beep quits as soon as the engine starts. It doesn’t seem to be the switch for the dome light as it goes out when the door is closed, and it will beep with the seat belt fastened before the engine starts. The fuse also runs the brake and directional lights. I wondered if it had to to with the electric trailer brake switch, but don’t know how to check it. I suggested the owner take it to an electrical specialist, which I am not. He is willing to pull the fuse every time he parks, rather than spend the money. He said he took it on a 600 mile one day round trip last month, towing his trailer that the brakes worked on. Life goes on.
The trouble might be with the switch for the ignition key. If disconnecting the connector going to it stops the problem then you know for sure it is the cause of the trouble.