1999 Express 2500 intermittent problem

[Hardwood Goat]

I recently purchased a van from an auto auction in Mn.173,000 4.3,4L80E, Drove the van back home to kansas and had a come and go problem along the way. Van ran great for about an hour than I could only give it an inch of pedal? Then cured and was normal,pulled into a toll booth to get my ticket and stood on it leaving the booth and the problem was back. So far fuel filter has been replaced, maf removed and cleaned with CRC. Starts and runs fine, in between fill ups on the trip it seemed that the rest helped but the problem reappeared later on, gas gauge needle vibrated quite a bit also but is accurate, HELP!!

[Hardwood Goat]

Little help? Bad fuel pump wouldnt work 100% then have symptoms as described? Read a similar thread that suggested replacing the maf.

[MT-2500]

Originally Posted by Hardwood Goat

I recently purchased a van from an auto auction in Mn.173,000 4.3,4L80E, Drove the van back home to kansas and had a come and go problem along the way. Van ran great for about an hour than I could only give it an inch of pedal? Then cured and was normal,pulled into a toll booth to get my ticket and stood on it leaving the booth and the problem was back. So far fuel filter has been replaced, maf removed and cleaned with CRC. Starts and runs fine, in between fill ups on the trip it seemed that the rest helped but the problem reappeared later on, gas gauge needle vibrated quite a bit also but is accurate, HELP!!

Confirm good fuel pressure when it acts up.


The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

[Hardwood Goat]

Maf was the problem. $50 from the junkyard and its cured!! Had a 240sx that had a similar issue but took awhile for it to register. I started to think about how the maf is heated after shutoff....and had an idea.

[MT-2500]

Originally Posted by Hardwood Goat

Maf was the problem. $50 from the junkyard and its cured!! Had a 240sx that had a similar issue but took awhile for it to register. I started to think about how the maf is heated after shutoff....and had an idea.

Thanks for posting back how it went.
Good luck