Fuel Pump

[sphillips]

I have a 2000 Z71, 5.7. About 4 months ago I had to replace the fuel pump. Worked great until a month ago, now when I turn the ignition on, I can't hear the pump run and the first start of the day takes a little longer than usual. All starts after that are normal, pump still doesn't come on, but starts immediately. No service lites or codes.

Any thoughts?

Thanks,

Steve

 

[sphillips]

Surely someone has a thought on this issue

 

[samotahoe]

defective pump. the pressure is going back to the tank on cold soak. there is a check valve on the pump that's saposed to stop that. so hence defective pump. you will need to make sure everything was replaced like the screen and stuff

 

[sphillips]

defective pump. the pressure is going back to the tank on cold soak. there is a check valve on the pump that's saposed to stop that. so hence defective pump. you will need to make sure everything was replaced like the screen and stuff

Thx Samotahoe. Pump was a complete assembly including qty sender. Even if the check valve is faulty, shouldn't I hear the pump run when I turn the ignition switch on?

Thx

 

[rockenthebowtie]

A good way to find out if it is a defective check valve is to cycle the ignition a couple of times before cranking that will build up pressure in the fuel line I also wouldn't trust a non gm factory fuel pump.. you may also need to check the fuel pressure regulator.. its mounted on the driver side of the fuel injector rail with a vaccum line connected to it.. a quick way is disconnect the vacuum line with vehicle on or off either way and if gasoline is pressent thats your extended crank concern.. hope that helps

 

[sphillips]

A good way to find out if it is a defective check valve is to cycle the ignition a couple of times before cranking that will build up pressure in the fuel line I also wouldn't trust a non gm factory fuel pump.. you may also need to check the fuel pressure regulator.. its mounted on the driver side of the fuel injector rail with a vaccum line connected to it.. a quick way is disconnect the vacuum line with vehicle on or off either way and if gasoline is pressent thats your extended crank concern.. hope that helps

I have a 5.7l, and according to my book, the fuel pressure regulator is under the upper intake manifold, so I will have to pull it. Does this sound right?

Thx

 

[rockenthebowtie]

It must be an early model 2000 meaning it still has the 99 engine and the CPI fuel injection system so yea the FPR on a 5.7 is under the upper intake... chances are you need the fuel injectors that came with a integrated fuel pressure regulator.. you need a fuel pressure gauge to test that one if you have access to a fuel pressure gauge I can let you know how to test it

 

[sphillips]

It must be an early model 2000 meaning it still has the 99 engine and the CPI fuel injection system so yea the FPR on a 5.7 is under the upper intake... chances are you need the fuel injectors that came with a integrated fuel pressure regulator.. you need a fuel pressure gauge to test that one if you have access to a fuel pressure gauge I can let you know how to test it

I've got several test gages in my aircraft mx shop, so should be able to rig something up.And yes it is the OBS with the 5.7l

Thx,

Steve

 

[rockenthebowtie]

Ok do you know where the test port shrader valve is.. thats where you need to hook up your fuel pressure gauge.. its on the fuel rail on the driver side behind the upper intake manifold next to the distributor... hook up your pressure gauge then craw under the truck... right under the driver seat area... now dont look under the driver seat you have to craw under the truck and locate the fuel supply line and the fuel return line.. for the most part the lines are metal but right there in that area you should see where they go from metal lines to rubber lines... your going to need some pinch off pliers.. 2 to be exact.i dont suugest it but if you dont have any you can use vise grips. the return line is the smaller of the 2... pinch that one off first cycle the ignition a couple of times and verify there are no fuel leaks at the fuel pressure gauge shrader fitting if none are present cycle the ignition one more time do not start the vehicle after the ignition cycle craw quickly under the truck and pinch off the fuel supply line leaving the return line also pinched off then your going to monitor the fuel pressure if your pressure drops the fuel pressure regulator is leaking.. if it doesn't after a few minutes. Meaning if it seems to be holding pretty good remove the pliers off the fuel supply fuel line only then look at the gauge if it drops pretty quickly then its going to be the check valve in the fuel pump.. hope it not to confusing and it helps let me know what your findings are.. good luck and may the force be with you lol

 

[sphillips]

Ok do you know where the test port shrader valve is.. thats where you need to hook up your fuel pressure gauge.. its on the fuel rail on the driver side behind the upper intake manifold next to the distributor... hook up your pressure gauge then craw under the truck... right under the driver seat area... now dont look under the driver seat you have to craw under the truck and locate the fuel supply line and the fuel return line.. for the most part the lines are metal but right there in that area you should see where they go from metal lines to rubber lines... your going to need some pinch off pliers.. 2 to be exact.i dont suugest it but if you dont have any you can use vise grips. the return line is the smaller of the 2... pinch that one off first cycle the ignition a couple of times and verify there are no fuel leaks at the fuel pressure gauge shrader fitting if none are present cycle the ignition one more time do not start the vehicle after the ignition cycle craw quickly under the truck and pinch off the fuel supply line leaving the return line also pinched off then your going to monitor the fuel pressure if your pressure drops the fuel pressure regulator is leaking.. if it doesn't after a few minutes. Meaning if it seems to be holding pretty good remove the pliers off the fuel supply fuel line only then look at the gauge if it drops pretty quickly then its going to be the check valve in the fuel pump.. hope it not to confusing and it helps let me know what your findings are.. good luck and may the force be with you lol

Thanks I'll try that test. Is there a specific pressure I should see on the gage?

 

[rockenthebowtie]

55-60 psi

 

[sphillips]

55-60 psi

Thanks, I'm a little late getting back into this issue, been very busy. Pressure is about 58psi. Assuming the Delphi pump I installed about 9 months ago is still good, it seems that if the problem was in fuel pressure regulator, each start would take the same amount of extended time, but it doesn't. After the first start of the day, the rest are pretty normal, starts immediately. So, if it could be the check valve in the pump allowing after sitting for the fuel to flow back into the tank, is that something I can fix., is it accessible. Hate to buy a new pump if I dont have to.

thanks for any help,

Steve

 

[lovemytaho]

defective pump. the pressure is going back to the tank on cold soak. there is a check valve on the pump that's saposed to stop that. so hence defective pump. you will need to make sure everything was replaced like the screen and stuff

HI Sir I have 02 Tahoe 70000 mile 5.3 No service engine light works great but as soon I rebuilt my transmission I went got my truck from shop now not working I check fuel press ok but as soon I start the engine slowly the gage comes down and shut off the engine but when I bleed the gas from the press gage the pressure goes up and truck works ok please can you help?