Truck starts hard, runs for a few minutes then shuts off?

JPARTINGTON

MEMBER
1998 CHEVROLET SILVERADO
5.7L
V8
4WD
AUTOMATIC
190,000 MILES

I recently replaced the fuel pump due to low fuel pressure and after the pump replacement truck didn’t seem to run any better. I think the pressure still seems a bit low. It’s about 56-58 with the key turned on. I can get truck to start and the fuel pressure at idle is about 55. Then after a few minutes the pressure drops to 40-45 and shuts off. I’m wondering if the fuel pump that I recently got is bad. I also did a leak down test, I hooked up gauge and started truck. I shut it off and looked at the gauge and it did not drop. So that means no leaks, correct? Any help would be greatly appreciated.
Thank you

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,772 POSTS

Hi,

The pressure is slightly low. It should be between 60 and 66 PSI with the key on and the engine off. See pic 1.

The idea that it drops but doesn't stop sounds like there is some kind of restriction. Did you replace the fuel filter? Was the sock at the bottom of the pump clean and in good condition?

Yes, to your question. If the pressure doesn't drop, there are no leaks.

When the engine stalls, does it start right back up? Also, when the fuel pressure drops, does it go right back up when you turn the key off and back on?

Let me know.

Joe

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Tuesday, November 22nd, 2022 AT 9:14 PM

JPARTINGTON

MEMBER
2 POSTS

I replaced the fuel pump because it had failed about a year ago and the fuel filter was replaced then. When it failed again just recently, I did not replace the filter, I thought it was new enough. After stalling it does not start right back up. When I cycle the key, it seems that the pump stops working for a bit because I get zero pressure on the gauge. Then after a bit it starts again. Almost like it’s overheating.

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Wednesday, November 23rd, 2022 AT 6:00 AM

JACOBANDNICKOLAS

MECHANIC
109,772 POSTS

Hi,

Have you checked the fuel pump relay? If there is no pressure and you need to wait, it may have failed.

The relay is in the under-hood fuse box. See pic below

Also, I need you to check something for me. When it stalls and you have to wait for it to start, see if it will start if you use starting fluid. If it does and then stalls, we can confirm a fuel issue. If there is no change, check to see if there is spark to the plugs.

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

I'm suggesting this because if there is no ignition, the fuel pump is shut down to prevent flooding. If there is no spark, you'll have no ignition or fuel. If that is the case, we may have a loss of spark.

If you have a live data scan tool, when cranking the engine (no start condition) see if there is an RPM signal on the scanner.

Let me know.

Joe

See pic below.

Image (Click to make bigger)