wont start, need direction

[Cityboy]

1996 c2500,  133,xxx miles,  5.7L Vortec
just put in a new Delphi fuel pump, Spectra sending unit, & Wix fuel filter.....still only getting 10-15 psi fuel pressure. 

it will instantly fire up & run with gas poured directly into the throttle body but dies as soon as fuel is consumed. relay has been swapped with another with no change. battery is good.

im thinking the old fuel pump,  sending unit, filter was fine. i REALLY need some direction here folks.

 

[Supreme Pizza]

I would look at the fuel pressure regulator. 

 

 

 

 

[txab]

Did you check voltage at pump

[Cityboy]

no i did not check voltage. should i check both plugs ?(2 prong on pump & 3 prong on frame)

[Supreme Pizza]

https://www.ebay.com/itm/New-Fuel-Pressure-Regulator-PR203-For-Cadillac-Chevrolet-Blazer-S10-GMC-Isuzu/171663875085?fits=Year%3A1996|Model%3AC2500&hash=item27f7f6dc0d%3Ag%3ADaIAAOSwdoNavHXT&_sop=15&_sacat=0&_nkw=1996+c2500+fuel+pressure+regulator&_from=R40&rt=nc

[Supreme Pizza]

Yep, like he said, it could be a voltage issue. That would cause the pump to run slower, and that would effect pressure. I'm not sure what would cause the voltage to drop, but it is theoretically possible. Maybe a bad ground?  If your pump is not working properly, then it will not build pressure. On the other side of the scale, you need "back pressure" to build fuel pressure. Unlike carburetor fueled engines, fuel injected engines have a pressure regulated fuel return line. If your return line is not restricted, you will never build pressure. It would be like trying to build pressure in a balloon that has holes in it. Doesn't matter how much air you push into the balloon, you will never inflate it. Could be supply, could be restriction. Ya just gotta test everything and figure out which one is the problem. Either issue is plausible. 

[Cityboy]

okay, thanks gents. ill be back tomorrow with either more questions or some kind of result.

[Cityboy]

ok,  a quick update.

i only had a little time to check the voltage at the relay fuse. all was good. i used a lil jumper to see if i could hear the pump running. all was good. 

that night my stepson informed me my lights were on. i go out to look and they are on but very dim & wouldnt shut off. hmm, nothing i could do at 11pm except hook up the charger to keep the battery from going to 0.

today after putting the pooch on the run i walk over to the truck and the damn thing fired right up.

so now my focus is going to be on the wiring inside the "under the hood" fuse box. should i be looking at something in particular besides corroded/broken wiring ?

 

[Supreme Pizza]

I would start with checking the connections at the computer, is there any water in there? You might take a look at all the main wiring harness grounds as well. Cleaning your battery connections might be worth doing as well. 

[east3021]

Here is the diagnostic for headlights not turning off on a 98. They have two tables for some reason. When they say “Headlamp and panel dimmer switch” that refers to the headlight switch on the dash. The “headlamp dimmer switch” or “headlamp switch” is the multifunction turn signal/low/high beam stalk. Their terminology stinks.

I’d guess that it’s going to be the same, or pretty close, to a 96. Hope it helps.

“Headlamps stay on...”



“Low beams stay on...”







Connector C266:








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[east3021]

I would start with checking the connections at the computer, is there any water in there? You might take a look at all the main wiring harness grounds as well. Cleaning your battery connections might be worth doing as well. 

I remember someone else having a similar issue. They found corrosion at one of the four VCM connectors, causing an intermittent ground and causing a crank/no start.


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