Hello!
I've got a 2004 Chevy Tahoe 4WD automatic w/ just over 200k miles. Bought it with a used replacement alternator and new battery installed for a few hundred bucks. I'm mechanically inclined, so I've done some things to diagnose the problem.
The issue I'm having is the truck won't stay running after starting. It's behaving as though the alternator is bad. I have done the following:
1. Tested the battery with a tester and voltmeter. It passed.
2. Tested to make sure PCM was sending signal to alternator. It is.
3. Replaced alternator with a new one mainly for peace of mind.
4. Replaced ground strap going from block to body and the one going from body to underside of the hood (relocated it to easier to reach location
5. Checked the other grounds on the truck for damage, corrosion, etc. A few were a little rusty, but no corrosion or damage from what I can see. I plan to clean them when it's day time.
6. Cleaned cable and ground connection between battery and alternator.
7. Right now I'm charging the battery since it's a bit weak from cranking so much. When I jump the battery with a box or another car, it will run briefly, then cut off soon as I remove the cables.
Hooked up my code reader, but of course that gives me nothing since I had to disconnect the battery a couple times.
Is there something I'm missing? What more can/should I do?
Thanks in advance for any help!
Quentin
Just curious but since you have a voltmeter have you checked voltage coming out of the alternator when running? Also I would check all the fuses in the truck
Yes, I checked that as well as best I could given that the truck wants to shut off shortly after starting. Voltage was low before and after changing the alternator. I checked the fuses, too. I can double check again though. Maybe I missed one.
Ya it’s always possible and better to be sure. In the past it sucks to hear I’ve had more than one bad alternator out of the box and it’s definitely annoying
You know, this type of thing happened to me. My car would start and then inexplicably shut off. Turns out, my fuel pump was failing. The fumes in the line would start the engine, but there was not enough fuel pressure to maintain it. Also, a clogged fuel filter might produce this same thing. If you've tried everything related to the spark the engine needs, look at air and fuel possibilities. Hope this helps!
If it dies after removing power but runs fine with power then fuel wouldn’t really make sense in this case
A car does need power to run. It only needs a little bit to maintain engine operation, but it must have power. If you disconnect the battery and the alternator from an engine, it will not run.
So after fully charging the battery, I gave it another shot. Same thing. I'm less inclined to think the issue is electrical, so at this point I'm moving on to checking the fueling system. Rented a fuel pressure tester and got about 47-48 psi at the service port with the key on engine off. Factory spec is 48-54psi. Gonna double check that the tester isn't leaking.
Since it is cheap, I'm going to change the fuel filter next. From there, I'll retest for fuel pressure and see if it goes up.
If no change, then I'm going to rent a noid light test kid to make sure the fuel injectors are in good working order.
I'm really hoping it isn't the fuel pump, because that job is a pain to do. Ugh
If your only really 1 psi off from spec I still do not think your problem is fuel related by what you described. If your taking away power and it shuts off it should be a power problem with cables connected it stays running then mechanically it sounds fine
Turned out to be a corroded ground wire!