1998 Pontiac Formula V8 5.7 L engine stalls, no power to DLC, PO441

I got a call feom the owner of the above vehicle. According to him, this has sat for about 12 years and decided to get it running again. He threw in a new fuel pump, fuel filter, drained fuel and put in fresh fuel, nw plugs, changed oil, oil filter, air filter. It run fine until the alternator seized and he put in a new alternator. However, the car started stalling.

I made a visual and notice some pest intrusion as evidenced by leaves and what not in the engine compartment. But since he says it run fine prior to changing alternator, I assumed that all wires are ok, with the PCM doing its job. I checked for:

1. fuel pressure, zero reading. checked integrity of fuel pump by disconnecting fp regulator and gas was squirting out of the housing. so i figured it was a bad regulator. fit in a new one and still stalls, with still no fuel pressure build up in the gauge.
2. checked tps and no glitches on open, close and snap of throttle;
3. tested the IAC and checked resistance of the pair of coil wires and they read 47.9 ohms and 48 ohms, i believe well within the 3 ohm difference. i still have to check the wiring integrity.

Any suggestions or perhaps encounters with the same symptons? thanks.

I would start by correcting the fuel pressure issue (as long as you're confident in your gauge). I haven't worked on one of those cars in a while, but I seem to remember that getting the tank out to change a pump was a pretty involved job. Sounds like he's been all up in there and now there's no fuel pressure.
Maybe the pump ground is poor or the pump itself is wired incorrectly, or maybe he did a great job and there's a different problem with the fuel system.

EDIT:. The post didn't address the no power to the dlc issue you listed in the title and I spaced on it by the time i finished reading, lol.
There's no power on pin 16, but it's not a no com since you pulled a p0441?

I'm with Noah, chase the fuel pressure issue. Maybe give it some carb cleaner and see if you can keep it running that way? Just to make sure you're on the right path.

I looked at the power distribution diagram, and didn't see much tying the alternator and fuel pump circuits together. Pulling the tank is indeed a challenge, but there is a body connector near the tank (on the underside of the car, right next to the ABS harness connector) that you can test at before going that far. It's C405 in the diagram below.

Thank you Tyler and Noah...
car has pressure now though reading only about 25 psi and surprisingly the car is responding well to acceleration, from idle to WOT and even at snap...(wondering if this is its normal pressure). I check power and ground underneath the car coming from relay, and harness connector, and had intermittent voltage supply. There was a two wire component underneath that that I cleaned and tapped, at the same time I tried to pich return hose going to fuel tank with the hope of increasing fuel pressure. When I started engine , it immedietely fired and idled flawlessly. My question is this: pinching the return hose help increase fuel pressure? Was the 2 wire component I was tapping some sort of a cut0ff switch /inertia switch? I wl try to take a picture of the underbody and post it.

I didnt look up the spec but i would have to say port injections usually run about mid 40's. I'm surprised it runs on 25, at least without coding or hesitating. There isnt anything on a gm car like that in between the fuel pump and the relay, like a ford. no power to the dlc could be a cig lighter fuse, and I wouldnt sweat that at this juncture.

Hi Tyler and Noah ...
Im attaching a picture of the component I was tapping on. Just wondering if you know what this is...

Fuel pressure Ok though hovering between 25-30 psi, and no more DTC PO441. This a FIX btw.

Thanks again, Robert.

p.s. Im unable to upload jpg file...

That'd be the EVAP vent valve. That and the P0441 might have been related? Tough to say.

30 PSI still sounds low, but it's tough to argue with results. :silly: Like Sterline80 said, I'd honestly surprised this starts and runs. No offense meant, but do you trust your gauge?

Pinching the return line SHOULDN'T produce a noticeable change in pressure, since 30 PSI isn't higher than the regulator set pressure. If pinching the return generates a bump in pressure, that'd suggest the regulator is leaking.

yes...the gauge is working fine...I checked my car with it and it read 57 psi.

would the vent valve then prohibit a fuel pressure build up?

robert.lesaca wrote: yes...the gauge is working fine...I checked my car with it and it read 57 psi.

OK gotcha! Not trying to insult your gauge. :silly:

would the vent valve then prohibit a fuel pressure build up?

Negative. If it were stuck closed, that might caused the tank to get sucked in... Stuck open would just piss off the EVAP monitor.