2500 express Van fuel problems, 305 vortec

Working on a 2002, 2500 express van with a 305. The van ran good at times then had trouble running at highway speed. The owner installed a Advance auto fuel pump, the trouble continued (pump 1),. He brought it in to be repaired, we installed a new converter because the original had been removed for some reason. The only code present after the converter was replaced is a random missfire. We checked the fuel pressure and found the van running @ ~55 psi and starting at around 57 psi. We then convinced the customer to let us install a AC Delco pump from the dealer at my cost of $323, he agreed and the pump was installed (pump 2). We checked the fuel pressure with the new factory pump and it wasn't much better than the Advance store pump it ran at about 57 psi. Well the customer needed the truck so off it went eventhough the pressure was low, it ran for ~5 weeks before the custome had to start beating on the fuel tank to get the pump to run. In the mean time the customer lost the dealer supplied receipt, now the dealer guys I've done bussines with for 30+ years won't replace the bad pump, they expect me to buy an new one. Customer doesn't understand, me either for that matter. We ended up with another airtex pump from Oriley's at an adithional cost of $201 (pump 3) once it was installed checked the fuel pressure it was 57/59 psi, we dead headed the pump the pressure went to almost 90psi. Next we decided to replace the fuel pressure regulator and while we're at it the van got an intake gasket. When we checked the fuel pressure after the new regulator was installed we had 62psi. I thought I was finally going to be satisfied, but that wasn't to be, as soon as the pump cuts off now the pressure falls off to 30psi within seconds and to zero in 5 minutes. It didn't do this with the old regulator so we removed the upper plenum so we could see the spyder, there were no external fuel leaks, we dead headed the pump again by installing a 3/8th pipe plug in the return line, the pressure will go to right at 90 psi and stays ~ 85 psi after the pump has been cut off. This van has become a PITA. We are planning to put some vaccum on the regulator tommorrow just to se if we can make it seal, if it doesn't I can only think the new regulator is faulty. Anybody got any suggestions? :banghead:

did you pull the injector nozzles out of the lower plenum to see if fuel ran out of them or just look at the spider itself. may have a stuck injector poppet? did you look at the missfire counter? where there any cylinders that missed more than others? I've had stuck injectors throw a random cylinder missfire code but when you looked at the misfire counter you could tell which cylinder was missing most.

We pulled all of the nozzels out and they were dry, We didn't look at the missfire counter, we're trying to get the fuel pressure where it ought to be, I think then the missfire won't be present, I hope. I'm tempted to purchase the van and burn it. Not really, I don't want any labor pay for this one I just want to see what it takes to FIX it.

i just did some reading on what info you gave us, but man i gotta go back to work. if you have no leaks and you are plugging off the fuel return line out of the back of the spider the problem has to be in the fuel pump. either a bad pressure hose or pump check valve. just for clarity where did you plug the return line at?

We took the return connection line apart right where the bellhousing and motor connect, to my supprise a standard 1/4" pipe plug screwed right in and bottomed out to seal the loop, no leak here either. I've had other suggestions that its the pump also but I don't see how considering the pressure stays up with the return plugged. I'm leaning toward the new regulator having some type problem, before changing it, the pressure didn't fall but it wasn't high enough either. Does that make sence? I'm off to some more of my hair out on this one, I'll check the forum later and post the findings, I'd sure like to finish this thing up today. Thanks for the help.

one other thing we are now working with the upper plenum removed and all of the nozzles exposed, with the fuel line connected so if I need to check anything else to do with the spyder now is the time. Thanks

What you describe may be a new bad fuel pressure regulator.
Key on engine prime up you should see 65-66 lbs of pressure with a slow leak down.
62 may even be the wrong application regulator.
Older system with 55/62 lbs spec.
I would replace the regulator with a dealer oem or a known good aftermarket with the right specs.

Full pressure on a good fuel pump should be 100-105 lbs of pressure.
Airtex fuel pumps have a lot of come backs and problem.
Best to stay with the AC-Delco/Delphi fuel pump.
Carquest dropped Airtex pump for that reason.
O'Riley's Knows it to but still sell them.
Pin them down on how many go bad.
O'Riley's can usually get the Delphi pumps for 25$ more on special order.
And always check for good voltage and ground to fuel pump.
The fuel pump plug and wiring in is a weak spot.

Also on the express vans the wiring plug in to pump on the transmission crossmember is a known problem.
I have had to wire around a lot of them.

Sounds like you already know but here is.
Guide lines for testing fuel pump pressure.

Always recheck check pressure after running truck a half hr.
And check voltage and ground to pump.
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.
A good pump on you modal should hit 96-105 lbs of direct pressure.
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 and fuel pressure testing guide line.
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.

Thanks MT-2500, I'd hoped you'd see the thread and chime in with J-mech. My customer is still upset with GM for not warrenting the AC pump that failed and choose to stay with the Airtex. Here is what has happened today. We fooled around with the first replacement regulator some and didn't like the 62 psi start pressure we had, so back to O-reily's for another regulator only they didn't have another one so we ended up at Advance auto. (GM dealer didn't have it in stock either) We installed the Advance regulator and had a good 65psi pressure before cranking, the pressure would bleed off to around 54 psi when the ignition was cut off, I didn't like it but ran out of options. We put it all back together as the upper plenum was still off. I installed a new Water pump while the intake gaskets were being installed and managed to turn the motor some while the Distributor was out so that killed an hour retiming the dist., we got the motor fired and set the cam retard (set dist. phase). We drove the truck with the fuel pressure gauge hooked up for ~30 minutes, riding down the road @ 45 mph it has 57-58 psi fuel pressure, when the motor is loaded the pressure runs 61-65 psi. this might not be exactly correct but Damn I'm sick of this thing and I'm going to have him try it for a while. At least now with the 65 psi pressure it cranks immediatly. When this Airtex pump fails I'll put another AC delco in it and start over. The AC delco pump has no more warrenty than the Airtex, wonder why, this was the first replacement pump from GM I've seen bad. Any more suggestions? Thanks

The dealer should have warranted it.

Very few Ac delco pumps go bad.

One problem is the wiring and wiring plug to them.
Low voltage or bad ground or lose connections.
Also the wiring plug kit with the airtex pumps should have wires soldered good.
Pitch the butt splice connectors that come with them.

In my opinion the wiring to the pumps is to light to start with.

Another thing to check is the fuel filter after run it a few days.
Sometimes when a pump goes out it leaves a lot of black stuff in tank that can stop up up a new filter fast.

If any more problems with it find another dealer or a good parts place and get a AC-Delco pump and fuel presure regulator.
Good luck with it.

The van is gone and the owner is satisfied with how the engine is running. He had one concern that I noticed also when driving it , now every so often it slams into overdrive or either converter lockup, I couldn't tell which. Could there be a wiring issue that can be common to the fuel pump and transmission. I guess I'll have him carry it to my transmission man next for analysis. It still doesn't have any codes though and thats a good thing far as I'm concerned. Thanks for the help.

You are welcome.

Hard to say on the wiring as both have seperate problems.
But bad voltage someplace or bad ground could make them both act up.

When the transmission is acting up get it checked out good.
Good Luck