Van wont start when hot

[brivy1900]

I have been chasing this for months. The dealer has no clue. My van, once it is hot wont start. If I turn it off then try to crank it over, it wont start. If I let it cool down about 30 mins, it will start. I have put a new coil, ICM, Cap, rotor and all that is fine and I checked even when van wont fire. The fuel pressure is 54-58. I have had conflicting stories on what the pressure should be. Would heat have an effect on the fuel pump and pressure? The van has quit on me once when i was driving for an hour and it was good and hot. It started to ideal really rough and then quit. I tried to crank it and it would fire then either. On one occasion I got it to start again, but then it started running really rough in about 10 minutes and started to choke it self out if I gave it any gas, it eventually killed. I have also noticed my fuel guage bouncing or vibrating in an erratic way.

Any suggestion or ideas?? PLEASE HELP ME... I HAVE HAD THIS TO SO MANY PEOPLE AND EVERYONE SEEMS CLUELESS.

1998 G1500
5.7L

[toddman67]

Fuel pressure should be 60+ psi and the irratic fuel gauge/ engine quits, sounds like you have a bad ground issue at the tank. Running the fuel tank low will cause these pumps to run hot and eventual failure as well.

[DFBonnett]

Often a failing ignition module will exhibit such symptoms when hot. You might want to get it tested.

[lemail5]

Sounds like a fuel pump issue...if it's the 5.7 liter VORTEC engine....you have to have a good 60psi or better fuel pump for initial startup. Delco\Delphi only...also, try adding a little fuel to the air intake when if fails to start again.

[MT-2500]

What year and what van and what engine and code?

Needs to be tested when it does it.
Any codes?
A good repair shop should be able to spot it.
Check around Ask around
Word of mouth.
Family friends coworkers neighbors business people and delivery people.
Mailmen and parcel delivery people get around and notice a lot of stuff.
Even a good parts house knows what shops are good and not good.
Chamber of commerce and better business bureau and city hall.
If you find a good referral to a repair shop go look them over and talk to them.
Look for a clean looking busy place with nice people running it.
Ask a few questions and ask about their qualifications and training.
Not all places have trained tech/mechanics.
If they do not find a place that does.
Even all dealers do not have all trained techs/mechanics.



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.

[brivy1900]

I put in a new pump, runs much better. I have noticed on a few occasions when I had to kick it down it would sputter or choke out for a second and then catch up. I have driven the van cross country and it worked pretty good. I did have to actually give the van gas with the pedal a couple of times to get it started. I onoy had to apply a tiny pedal pressure. any ideas. Is there a sensor that regulates that. (IAC) ?

[MT-2500]

We need fuel pressure test.
Post back your resdings.

[brivy1900]

Fuel pressure is 65lbs. still having the bogging out issue as though it is choking itself out. Could a VCM that is corroded or appears to have moisture in it cause this issue. I have replace now the pump, fuel filter, ignition module, coil, plugs, wires, and dist cap and rotor. The van is not shutting down now when it gets hot, but now its seems to want to choke out if I hit the accelerator. ????????????????????????? ANY INPUT WOULD BE GREATLY APPRECIATED

[MT-2500]

Originally Posted by brivy1900

Fuel pressure is 65lbs. still having the bogging out issue as though it is choking itself out. Could a VCM that is corroded or appears to have moisture in it cause this issue. I have replace now the pump, fuel filter, ignition module, coil, plugs, wires, and dist cap and rotor. The van is not shutting down now when it gets hot, but now its seems to want to choke out if I hit the accelerator. ????????????????????????? ANY INPUT WOULD BE GREATLY APPRECIATED

You need to run the complet fuel pressure test again and post back pressure readings.
Also get the engine hot and check fuel pressure on the road when it bogs down.
Any engine codes?
What is the engine vacuum at adle and at 2 K RPM?

[Schrade]

Static and dynamic fuel pressure tests, hot, AND cold.

Static - motor off, fuel lines primed, note pressure, AND note pressure-let off time (post how long before it goes to 0). If it goes down too fast, you have leaking injectors, or a ruptured diaphragm in the fuel pressure regulator. Both will affect hot start.

Check the vacuum line to the fuel pressure regulator for a ruptured FPR diaphragm - smell the vac hose for a STRONG gas smell.

Dynamic pressure - gauge on pressure valve, motor on. Note continuous idle pressure, WITH vac hose OFF of FPR. Then put vac hose on, note pressure, then pull the throttle linkage, and note if pressure INCREASES. This is acceleration enrichment - response to increase vacuum, even tho' more fuel is pullin' from the line.

Write results, and post back on this...

[Fecklar]

I had the exact same issue with my Express van. 1998 2500 with a 5.0 litre engine. It was bogging down the same way. Mine ended up being the VCM. It was corroded as well. It is located in a very bad spot. Runs great now...