jGARZA

Hey guys! Im new to the forum, hope someone can point me in the right direction before i spend thousands of dollars and hours doing it wrong

I have a 96 gmc sierra, all stock running gear, 350 auto 2wd. I bought this truck last week from a good friend & coworker. I live about 40 miles from where I picked it up. I drove it home and parked on the curb, truck ran great! I came out the next morning & that's where my problems began. The truck would fire when I put the ignition in the start mode then die in 3-5 seconds once in run mode. It showed a 1/4 tank of fuel on the gauge but to be certain I added 2-3 gallons & nothing changed. I Changed out the inline filter on the chassi & also cranked the motor with the line disconnect on the"out" side of the filter to make sure fuel was pumping through, it was. I pulled the air intake & could make the motor run by pouring fuel into the intake. I ended up draining the battery doing all this testing. I came out a couple days later & hooked it up to my neighbors truck & with it in the driveway (on a slight incline) it would not fire unless I poured fuel into it unlike the first day it would start but not run. I played with the ignition while pouring fuel into it, holding the key between start & run but no change, pretty pointless at this point since fuel wasnt even getting to the motor it seemed. The first day I listened for the fuel pump & could hear it working with the key on but only for a couple seconds then it turned off (pretty normal) I assumed. The next time I messed with it I forgot to listen for it but since the truck wouldn't even start I'm guessing the pump finally died? battery is out and on the trickle charger until i get some good advice.

First question. What's the best way to test the fuel pump w/o pulling the tank?

2. If its possibly the ignition can I test that w/o pulling it out?

3. Is there any sensors or relays that can cause this I.e. smog/emmisions or fuel relays

4. Is there anyway to see if fuel is reaching the motor somewhere on or around the upper intake manifold?

5. If the pump is the culprit is it a good idea to grab a pump from the wrecking yard?

6. Are the autozone fuel pumps good enough?
7. If I have to put a new pump in should I drop the tank or pull the bed? Its a step side.

I'm not a mechanic so if I'm forgetting a question or a step or two please let me know. All help is greatly appreciated. This is my first ride so I'm eager to learn & excited to drive it!

jGARZA

wow 60 people viewed my post and no one can help me? is it because i posted in the wrong section? does GMC have there own forum? i thought GMC and Chevy were identical other than a few minor differences.

OLD WRENCH

No you didnt post in the wrong section. Its obvious from your description you are not getting fuel.You need to check the fuel pressure. Just because it pumps some doesnt tell you much. If the pressure isnt up to what it should be it wont work. Removing the bed seems to be the preferred method to change a pump.Vehicles of today require special tools to diagnose,and if you dont have them you are guessing.

Jdog07

The fuel pump will run for a few seconds to prime the system. If you turn the key off and turn it on again in a few minutes it may not come back on because the system is still primed. You should be able to get a pressure tester from an auto parts store or you can try another way.

Disconnect the fuel line running to your throttle body and have some one turn the key on. Fuel should spurt from the line. If it is the pump it will only trickle out. You'll be able tell the the difference. either lots of pressure or not

jGARZA

Alright thx guys, ill check it out & let you know.

davecoleman7

These guys are right, i have a 96 silverado with the vortec 350, it requires 65 psi for it to run. go to autozone or its equivalent and buy a cheap fuel pressure test guage. (about $20.00), and a repair manual. every vehicle is different, so you will have to investigate a little to determine what your fuel pressure should be. there should be a test port on your fuel line before it goes into your engine (right side)