Pardon me for interrupting a great thread... Shurkey and 1990Z71Swede. Your knowledge is good stuff!
Slow-c1500, have you ever replaced your O-Rings..?
Sometimes at the tank fuel lines, sometimes at the manifold lines, sometimes at the injectors.
Unless you make certain the fuel lines have brand new o-rings everywhere, you can chase this for weeks.
You could have several leaking intermittantly, if they have never been done since 1996.
Especially living in a hot sunny climate.
The ones at the tank could be square, or the fittings loose, when you pull the lines and inspect them.
When I pulled my lines, somebody had used green A/C o-rings and they were all blown out from gas.
You could have the wrong rubber at any sealed connection, performed by somebody who did not know what Nitrile Rubber is and when it is specified.
The flex lines over my transmission were rubbed through my braided lines... not leaking though...
The fuel tank O-ring on the lid of the tank could be cracked too. It's 3"diameter x 1/4" if you have the older style tank or a replacemnt aftermarket installed by somebody else. Unless you know what you have... it's all guess work.
You are not supposed to use gasket sealer on a fuel line o-rings either... but some people do anyways.
It could leak and cause a fire. Sometimes, the guy before you or sun shade auto sales mechanic used gasket sealer somewhere and sold the truck. Especially if you have the 3" o-ring at the tank cap cracked.
Look for a stain on top of the fuel tank from fuel leaking onto it from the lines or around the main tank seal.
My advice is to start here with these parts and then test again:
https://www.oreillyauto.com/shop/b/...omotive-truck-1996-chevrolet-c1500-pickup-rwd
Change all the fuel line seals end to end.
I have had right out of the box brand new auto store fuel pumps with a bad check valve before too.
The small black hose inside the fuel tank to the pump goes rotten or leaks too.
Change everything if you drop the tank. O-rings, main tank seal, fuel hose, fuel pump, strainer.
Now you know everything is good and it will likely last a long while.
$150-$200, a tough day with a full fuel tank and a few friends who do not smoke.
The tank is almost always near full when this happens...
Try to buy a Delphi or ACDelco pump, if you can find one.
Save the old pump for a spare when you find square o-rings and/or a rotten small rubber hose someplace, but change it anyways.
The small rubber hose inside the tank is completely different rubber than regular Gates Barricade 300 PSI TBI or TPI fuel line.
It is rated for submersion in gasoline.
The small hose will rot very fast if you install improper inner tank hoses with the wrong type of rubber hose.
Crumbs from the correct but rotted small line can screw up the pump and check valve, so change it all out.
The pumps don't last long and at least you will know the tank, lines, filter and rear fuel system is 100% new.
Then move upstream to injector seals and FPR diaphram, and restart your testing... if you still need to.
Buy a few extra small o-rings so when you drop or break one, you'll have an extra few on hand.
The injectors leaking cannot be verified unless all the fuel line seals are 100% with the test you are performing, in my hubmle opinion.
Lastly, if you buy a pump from a parts store, verify it is the correct pump pressure before you drop the tank.
Tripple check the numbers on the actual pump match the box and the box matches your engine VIN.
I have performed this repair, on my 1999 4.3 Vortec V-6, at 9PM in a grocery store parking lot with 5 cops watching.
The parts store sold me the BOX with a new 46psi pump and had to do the entire tank drop repair by myself, all over again.
Luckily the parts store was opened to 12PM and I got there at 2 minutes to 12 for the proper pressure fuel pump, when it still would not start, without 60 PSI. The cops gave me an ovation when it started, which was kinda humiliating at 3AM.
The second time, it was easily 1/2 hour faster.
If the suggestions in my post was already verified, please pardon me for missing something guys and girls.
Good Luck!
Slow-c1500, have you ever replaced your O-Rings..?
Sometimes at the tank fuel lines, sometimes at the manifold lines, sometimes at the injectors.
Unless you make certain the fuel lines have brand new o-rings everywhere, you can chase this for weeks.
You could have several leaking intermittantly, if they have never been done since 1996.
Especially living in a hot sunny climate.
The ones at the tank could be square, or the fittings loose, when you pull the lines and inspect them.
When I pulled my lines, somebody had used green A/C o-rings and they were all blown out from gas.
You could have the wrong rubber at any sealed connection, performed by somebody who did not know what Nitrile Rubber is and when it is specified.
The flex lines over my transmission were rubbed through my braided lines... not leaking though...
The fuel tank O-ring on the lid of the tank could be cracked too. It's 3"diameter x 1/4" if you have the older style tank or a replacemnt aftermarket installed by somebody else. Unless you know what you have... it's all guess work.
You are not supposed to use gasket sealer on a fuel line o-rings either... but some people do anyways.
It could leak and cause a fire. Sometimes, the guy before you or sun shade auto sales mechanic used gasket sealer somewhere and sold the truck. Especially if you have the 3" o-ring at the tank cap cracked.
Look for a stain on top of the fuel tank from fuel leaking onto it from the lines or around the main tank seal.
My advice is to start here with these parts and then test again:
https://www.oreillyauto.com/shop/b/...omotive-truck-1996-chevrolet-c1500-pickup-rwd
Change all the fuel line seals end to end.
I have had right out of the box brand new auto store fuel pumps with a bad check valve before too.
The small black hose inside the fuel tank to the pump goes rotten or leaks too.
Change everything if you drop the tank. O-rings, main tank seal, fuel hose, fuel pump, strainer.
Now you know everything is good and it will likely last a long while.
$150-$200, a tough day with a full fuel tank and a few friends who do not smoke.
The tank is almost always near full when this happens...
Try to buy a Delphi or ACDelco pump, if you can find one.
Save the old pump for a spare when you find square o-rings and/or a rotten small rubber hose someplace, but change it anyways.
The small rubber hose inside the tank is completely different rubber than regular Gates Barricade 300 PSI TBI or TPI fuel line.
It is rated for submersion in gasoline.
The small hose will rot very fast if you install improper inner tank hoses with the wrong type of rubber hose.
Crumbs from the correct but rotted small line can screw up the pump and check valve, so change it all out.
The pumps don't last long and at least you will know the tank, lines, filter and rear fuel system is 100% new.
Then move upstream to injector seals and FPR diaphram, and restart your testing... if you still need to.
Buy a few extra small o-rings so when you drop or break one, you'll have an extra few on hand.
The injectors leaking cannot be verified unless all the fuel line seals are 100% with the test you are performing, in my hubmle opinion.
Lastly, if you buy a pump from a parts store, verify it is the correct pump pressure before you drop the tank.
Tripple check the numbers on the actual pump match the box and the box matches your engine VIN.
I have performed this repair, on my 1999 4.3 Vortec V-6, at 9PM in a grocery store parking lot with 5 cops watching.
The parts store sold me the BOX with a new 46psi pump and had to do the entire tank drop repair by myself, all over again.
Luckily the parts store was opened to 12PM and I got there at 2 minutes to 12 for the proper pressure fuel pump, when it still would not start, without 60 PSI. The cops gave me an ovation when it started, which was kinda humiliating at 3AM.
The second time, it was easily 1/2 hour faster.
If the suggestions in my post was already verified, please pardon me for missing something guys and girls.
Good Luck!
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