2000 Jimmy stalls on highway

[mcstar 58]

I have a 2000 GMC Jimmy 4x4 (4.3) with 79,000 miles. Original owner.
I drive it on some weekends on a 5 hour (300miles) drive one way. Several times, only on the way back (halfway) the car stalls, I coast to the side and it starts right up, some times it will do it again 1/2 hour later. It has not done this on the way up (so far).
last month i did three trips and nothing happened. Then last time it did it again (on the way down!) 3 times with the last one near my home at a light it stalled but took a few minutes before it started back up. You can drive all day around town and it runs great.
I have noticed that when it is cold it has not happened, but when it has happened it is 60 or warmer?
Anyone have any ideas or suggestions or solutions? Thanks

[tempfixit]

How much gas is in the tank when this happens?

Have you checked the battery cable connections for corrision or looseness?

Does check engine light come on?

Have you checked for any codes?

You may want to attach a fuel pressure tester to windshield wiper or mirror and watch what your fuel pressure does when this happens.

[mcstar 58]

About 1/2 tank full.
No codes present. No check engine light.
Will check battery cable tomorrow.

[mcstar 58]

Update: I decided to take a chance and drove it upstate this weekend!
I left friday night (it was cold out) and no problems all the way.
Sunday i drove down, left it was 32 degrees and arrived it was 53 degrees and it ran fine all the way! (average 19mpg) This time it did not happen .
Can it be affected by the outside temp?... or just a coincidence?

[GunsOfNavarone]

Stalling on the highway at high speeds and then restarting, and also stalling at stop signs is often a sign of a bad ignition switch. In my 1997 Bravada I have relaced the ignition switch twice for the above problem, and the fuel pump once. Both the ignition switch and fuel pump can cause the stalling at highway speeds, but the stop sign stalling when combined with highway speed stalling has always been the ignition switch.

[mcstar 58]

I have made 2 trips (since posting) and it has not stalled...BUT.... last night before shutting it down i heard a buzzing sound....... and as i rolled up the door glass and held the power window button down (after glass was up) the sound got louder. Everytime i hit the switch the volt gauge dropped a few notches (with interior light on) , then back up to 14 when i let go of switch. Noise is comming from feul tank area (pump?)
I have noticed recently that the volt gauge sometimes go's down one notch while driving (14.1 to 14.0) so i had alternator checked and they said it was charging good.
This morning it is charging at 14.1 (where it always has been) and no buzzing noise.
Is the pump draining the current or not enough current to pump?
I will invest in a fuel pressure tester later this week and post result's in the mean time any suggestions??

[mcstar 58]

OK I did a pressure test today.....
Cold - turned key on went to 62 then dropped to 54.
Hold's @ 54 does not go down (waited 5 min.)
Drove a little then went on highway.
Driving at 65-70mph, pressure is 54-56.
Back home at idle it is @ 52.
Shut it off, it goes to 58 for a few seconds then down to 54.
It then creeps slowly up to 58 (keys off) and holds there for a while.
I checked it 10-15 min. later and it went down to 40.
I could not find a way to pinch return to check the pump pressure.
Let me know if I should do anything else.
Thanks

[b1lk1]

That pressure is low. You have a definite fuel issue. I will forward you a PM I received from old_master (he deserves all the credit for the info inside it) that will give you a much better overview of what you need to be seeing from your pump and how to test it.

[duke350]

Before you mess with the pump you might want to change the filter. It seems like the pump is ok when cold, but a bit low when warm. The pump is usually the first thing people blame on these things, but it is not always the problem. If the pump is intermitent then you would have a chug chug, like its out of gas, when it stalls. If it is something in the ign it will be as if the key was shut off while driving. I have seen them run with much lower then posted spec. I have also seen them on the low end of spec and not run. Pump should be at 60-66 psi while pump is running and engine is off, like in the prime cycle. After it primes it should drop to 55 psi and hold for 5 minutes. I am not saying you do not have a fuel pump problem, but there has been plenty of people who have been convinced they have a pump problem, bought and installed a brand new delco pump, and still had the exact same problem. If you can, get the gauge taped to the windshield, or where you can see it, and drive it and take note what the pressure does when it stalls or acts up.

[safety dude]

yes check , no change the fuel filter !!!! problum should go away if not iy is probobly the fuel pump i do bleave its in side the fuel tank good luck its worked for me !!!!!!!!!!