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Fuel pump or pressure regulator

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78K views 4 replies 3 participants last post by  The STIG  
#1 ·
Hi,

I'm a new guy here. Glad to find a forum for GMC owners!

I do have a question though. My truck is getting hard to start if it sits longer than 10 minuets. Dosen't matter if the engine is cold or warm. When I try to start my truck, I need to turn the key to the run position without starting the engine at least 2 or 3 times to get the engine to start.

I checked the fuel pressure at the fuel rail on the right hand side of the engine (5.3 V-8). I have 50 PSI running. When I turn the key off, the pressure will drop to 15 PSI almost immediately. It takes about another 2 minuets to drop to zero. When trying to start the engine and watching the pressure guage, the first 1 or 2 turns of the key will get the pressure up to 55 PSI. Then the truck will start without any issues. Truck runs fine after the engine starts. No OBD codes. 18 MPG.

I have been told that there is a check valve in the fuel pump to hold the pressure when the key is off. Could this be the problem or the pressure regulator?

Hate to just start changing parts till it starts woking again.

I have changed the fuel filter about 3K miles ago.

Thanks in advance
 
#2 ·
pull the vacuum line off the fuel pressure regulator see if any fuel comes out. (if so replace the regulator)
have you tried turning the key to the run position and letting it sit there for 3seconds or so? (with the key on you should have pressure) if just turning your key to the run position dosent give you any fuel then i would check the ignition or suspect the fuel pump...
 
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#3 ·
Well, got everything working! It was not without drama though...

My job kept me out of town for a week, so I wasn't able to work on my truck or post for a week.

There was no fuel leaking at the regulator so I bought a new fuel pump.

My buddy and I started out this morning and everything seemed to be going fine. Dropped the tank, swapped out the fuel pumps and had the tank back under the truck in about an hour. We then had the bright idea to test the fuel pump before we put the tank back into the truck. This is where our headaches started...

The new pump came with a different plug that we had to install on the wiring harness. 4 wires, 2 for the pump and 2 for the fuel level guage. We put it on, plugged it in, hooked up the fuel lines, turned the key on and nothing happened!

No power to the pump. We triple checked all of our new connections, checked fuses, relays everything we could think of.

We ran temporary separate wires to the new fuel pump from the battery and the pump now worked!

It then occured to us that we probably had a ground issue.

When we dropped the tank, we unbolted the ground strap that is on the fuel filler neck, we didn't see the other wire that came off at the same time. It was a ground wire that comes out of the wire harness and attaches to the bed with the ground strap for the filler neck. As soon as we attached the ground wire the pump started when we turned the key, engine started, good pressure and it held pressure after we turned it off. 30 minuets later we had the tank installed and the truck ready to drive.

This little oversight on the ground wire cost us about 3 hours of poking, scratching our heads and a lot of frustration.

Hopefully our oversight on the ground wire and this little post will help someone else out in the future.

Thanks,

H2Os50
 
#4 ·
haha good story, glad to hear you go it fixed.
 
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#5 ·
H2OS50 said:
Well, got everything working! It was not without drama though...

My job kept me out of town for a week, so I wasn't able to work on my truck or post for a week.

There was no fuel leaking at the regulator so I bought a new fuel pump.

My buddy and I started out this morning and everything seemed to be going fine. Dropped the tank, swapped out the fuel pumps and had the tank back under the truck in about an hour. We then had the bright idea to test the fuel pump before we put the tank back into the truck. This is where our headaches started...

The new pump came with a different plug that we had to install on the wiring harness. 4 wires, 2 for the pump and 2 for the fuel level guage. We put it on, plugged it in, hooked up the fuel lines, turned the key on and nothing happened!

No power to the pump. We triple checked all of our new connections, checked fuses, relays everything we could think of.

We ran temporary separate wires to the new fuel pump from the battery and the pump now worked!

It then occured to us that we probably had a ground issue.

When we dropped the tank, we unbolted the ground strap that is on the fuel filler neck, we didn't see the other wire that came off at the same time. It was a ground wire that comes out of the wire harness and attaches to the bed with the ground strap for the filler neck. As soon as we attached the ground wire the pump started when we turned the key, engine started, good pressure and it held pressure after we turned it off. 30 minuets later we had the tank installed and the truck ready to drive.

This little oversight on the ground wire cost us about 3 hours of poking, scratching our heads and a lot of frustration.

Hopefully our oversight on the ground wire and this little post will help someone else out in the future.

Thanks,

H2Os50
Click to expand...
Sir

Your post was of a GREAT help to me today. I had to change my fuel pump in my 2001 chevy 1500 Z71 due to it's failure. I did just what you and your friend did as far as testing the pump with the tank on the ground before reinstalling it and had the same problem with the pump not working. I started checking fuses finding nothing wrong and was about to run power from the battery to test the pump when I desided to do a google search and found your thread. As soon as I got to the part about the ground wire I knew what I had done wrong and solved the problem. Your post saved me a good hour of messing around and stress on a hot day.

Thanks for posting your story. It was of help to someone, me.

Thanks again. Great forum.
 
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