1996 GMC K1500 Pickup Starting Problem

Is this an s10? If it is, check the wiring harness on the driver's-side of firewall under cowl. Sometimes it gets disconnected about 1/8'', then it won't start...cheers

bad fuel pump or fuel pressure regulator.

Have you sprayed fuel/starting fluid into the engine to see if it starts? You can have fuel pressure but no injector fuel delivery, we call this "pulse"

have you checked for spark with vehicle off take a plug out leave it in plug wire but remove it from engine have another person turn key you should see spark from plug on valve cover hold plug close to valve cover dont hold plug hold wire part of it if you dont have spark replace coil pack or distribrator did you bleed fuel line to get air out also before you do this try replaceing fuel pump relay fuse its under hood in the fuse box it might be blown but since you said its getting fuel to rail thats not it but since you said starting fluid starts it its got to do with the fuel because its not fire because it started up so its in the fuel part replace fuel pump relay its easy to do its under hood its marked on the inside cover which one it is did yous bleed the fuel lines if not its also easy on your fuel rail underhood have another turn key but not start truck as they turn key you open bleeder screw then close screw have them turn key off have them do this a few times until you have a steady stream of fuel good luck if this helps give me a good rating if you need any more info just write me back

When you turn the ingnition switch to start can you hear the fuel pump humming?

Hello. There may be a couple of issues here. First of all, how do you know that the car is low on gas and not almost out of gas? If you are using the fuel gage as your only source of information, I know that many older pickup gages are way off. I have one friend who runs out of gas when his gage gets to 1/2 tank. That all said, it sounds like your fuel pump is going south!

even though parts are new they also come with defects so it sounds as if when you turn the key you hear it working and other times not at all hmmm connections are tight ? could be faulty fuel pump or relay .

Couple of things, when you turn the ignition key to the run position, you should here the fuel pump "hummmm" for roughly 2 to 5 seconds.
If you can not here the pump run, check the fuel pump fuse under the hood.
If that is OK, find the fuel pump relay in the same fuse box and swap it with another relay that looks just like it and try to start.

Also, there is a fuel pump prime wire located up near the brake master cylinder or firewall area. It is a single gray wire with a RED connector on it. If you jumper battery voltage to that wire, you can run the pump.
Good luck, let me know.
Regards,

The theft light issue is a good observation. Have you replaced the key tumbler or an ignition component lately? Has there been a lightning storm close very recently?

What the flashing security light is indicating is an attempt to relearn the key you are using.
Turn the key to run position, allow light to flash for 10 minutes, when light stops flashing turn ignition to OFF position for 5 seconds, turn ignition to run position and start over. Do this for 3 consecutive cycles, the the theft system will relearn the key cylinder code and store it once again.
Try that first before you go any further.
Let me know what you find.
Regards,

Take off your gas cap and have someone stand there with thier ear at the hole, (no smoking), turn the key to on just before start and they should hear the fuel pump humming. if they dont then try to start. if it doesnt start turn key off and at that instant the pump should be heard again. What i think is happening is your pump is not energizing . Its supposed to energize when turning your key on and off. This can be caused by a bad fuel pump or pump relay switch. Hope this helps. please rate me