95Astro--Intermittent Stalling, Pressure Regulator

:banghead: 1995 Astro AWD
4.3L "W"
165,000 miles
NO STORED CODES

The engine began stalling and dying about three weeks ago. When it first died, it started immediately and ran fine for a week and a half. Then, it started stalling more often but would still start right back up. Three days ago it died and wouldn't start for over 12 hours. When the ignition was turned on, the fuel pressure would jump to 64 psi and hold, but the engine wouldn't start. There was plenty of spark at the plugs, and while checking for spark, the engine started. I almost made it home when the van died again, but this time when it died, the fuel pressure dropped to 0 psi. After a few attempts, it started but died again in my driveway while ideling, and the fuel pressure held at 58 psi.

The van would start immediately after dying with out turning the ignition off, and the fuel pressure continued to hold at 58 psi. Most of the times the engine died, I would leave the key on and test the TPS (back-probing the dark-blue wire produced a smooth increase and decrease in voltage from 1.0v to 4.8v, every time). The reason I keep testing the TPS is that I posted on 2-15-2007 with an intermittent stalling nightmare. 666319

This afternoon, every few times the engine would die, the fuel pressure drops to 0 psi, but slowly builds to about 40 psi after 15 minutes, and would climb another 2-4 psi over the next 10 minutes. Only two or three times during the last few days would I detected a gas odor in the engine compartment.

Last fall I replaced the injector unit because the fuel-pressure regulator took a dump, but I didn't replace the nut kit because there didn't appear to be leaks. I suspect the regulator, but the odor of fuel make me wonder: could a leaking nut kit cause an intermittent stalling problem? Is there anything else I should test before replacing the injector unit?

Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Tape a fuel pressure gauge to outside of windshield.
Check engine running on the road fuel pressure for 15 to 20 minutes driving.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Full pressure should be 75 lbs or more.
Your specs engine running specs should have 55/61 fuel pressure.
Cold start should be 60lbs 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 around 58 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.
Also if fuel pressure is dropping when engine stalls check for 12 volt power feed to fuel pump.
MT

* Whether cold or hot, it starts easily, except for the 12 hour period that it wouldn't start.
* Cold start pressure is 64 psi.
* Running pressure is 58 psi.
* The pressure guage has remained connected the past three days.
* While running, the pressure is 58 psi cruising, up to 64 psi accelerating.
* 8 out of 10 shut offs, the pressure holds above 58 psi, but for the other 2, pressure drops to 0 psi, then slowly increases.
* Cold start pressure while return is blocked exceeds 75 psi.
* Usually when stalling, the pressure does NOT drop, and there is 12 volts to the pump.

Please, read all of my first post to this thread. Sometimes before stalling, the engine surges for a few seconds, and the pressure fluctuates between 58 and 62 psi; usually, pressure remains above 58 psi after the engine stalls, but rarely, it drops to 0 psi. Even when the pressure dropped to 0 psi, the engine would start right back up.

The fuel pressure sounds good.
Check for lose of spark or injector pulse whe it stals or quites.
Good luck MT

No lose of spark.
How do I check injector pulse?

The injector unit was replaced 4 1/2 months ago.

sounds like injector prolem if your smelling gas and so not getting enough gas...

The fuel odor only occured a couple of times out of over 30 stalls, and it still makes me wonder about possible leaks in the fuel lines within the upper intake. By the way, why are they called a nut kit?:dunno:

Also, since the fuel pressure occasionally drops to 0 psi, I am concerned that there might be a problem with the fuel-pressure regulator.

FYI: I also replaced the fuel filter and purged the fuel-supply line--just for the fun of it. The tank is full and is never below 1/4 tank. The oil pressure stays about 45-50 psi. The engine stalls while idling, accelerating, cruising, and occasionally while decelerating; although, there had been times while cruising that the engine started to stall but resumed running when I let off the gas pedal.

A scanner or a noid light.

Is there anything other than the fuel-injector unit that I should consider testing?