1982 GMC C3500 Fuel pumps

DEFIANTADP

MEMBER
1982 GMC C3500
V8
2WD
AUTOMATIC
85,000 MILES

Ok here is a problem I am having working on my 82 GMC 1 ton dually w/ 454 carb.

I have replaced the fuel pump because as it was turning over I was getting no fuel to the carb.

After replacing it I had the same problem.

I thought the fuel pump just dried up as the truck has sat for over a year not being started or driven.

Well we had a fuel tank switch over valve go out on my brothers truck and thought maybe it was that even though I could hear it switching over so I replaced it and still no fuel to the carb while its trying to start.

I took the fuel line off the carb and placed it in a 20oz. Plastic soda bottle to watch it if it started pumping so far NOTHING! So I siffened gas from the truck useing the fuel inlet that gos into the fuel pump and it is free and clear and flows gas freely. Have I told you how bad todays gas tastes! Give me the good stuff with some lead in it! LOL

the lines are on the correct fittings on the pump as the one with the threaded fitting gos to the carb and the 3/8 hose fitting that says IN is from the fuel tank. And the 1/4 inch hose is the vent.

I took another 20 oz bottle and fitted it to make it a small fuel pump to get the truck running and maybe long enough to get the pump going fast enough to start pumping gas still nothing!

the fuel pump is a air tex 40963 and looks to be the same one required by all the parts store on line auto zone and Oriellys and advance auto parts. I would'nt think I got 2 bad pumps unless there is a bad batch but that is unlikely. And yes the the fuel pump push rod is in the thing too as I had to fish it out and put a dab of grease on it to keep it up out of the way while I slide the pump in the thing.

I dont want to go electric I dont enough $$$$$$$ to get a good one and I just need to get this going to sell.

any one got ANY IDEAS?

5 Replies

RASMATAZ

MECHANIC
75,992 POSTS

What do you have a Carb or a TBI?

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Thursday, September 10th, 2009 AT 8:35 PM

DEFIANTADP

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6 POSTS

Like I stated in the message carb. Not TBI

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Friday, September 11th, 2009 AT 1:09 AM

RASMATAZ

MECHANIC
75,992 POSTS

You'll be surprise how many people calls the TBI a Carb-

Why don't you check the fuel pressure with a fuel pressure gauge designed for your fuel system and get back with the readings and also check for injection pulses.

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Friday, September 11th, 2009 AT 6:19 AM

DEFIANTADP

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6 POSTS

While cranking the engine and the fuel ine off at the carb there is no pressure that I can feel with my thumb over the end of the line. There is also no pressure at the pump and there is no vacumn at the pump inlet side doing the same test cranking the enigne and simply putting a thumb over the end of the line or fittings. It acts like the cam lobe or the fuel pump rod is not there but it is and has nearly a inch of stroke. It must be another bad pump is all I can think of. Air tex must have had a bad batch or something.

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Friday, September 11th, 2009 AT 9:06 AM

DEFIANTADP

MEMBER
6 POSTS

MY fuel pump problem is fixed !
After installing 4 Air tex part number 40963 fuel pumps It took a fuel pump off my older chevy truck a 1971 with a big block chevy also. And installed it on my 82 GMC dually with the BBC 454. The only difference in them is the 40963 has a vent line that gos back to the tank. Air Tex must have a very large amount of these with a internal valve problem because it wont pull enough vacumn to pull gas from the tank. This tells me there must be a internal leak in them. I tested the pumps at the store and while they have some vacumn they don't have enough or do they push the full to the carb. So If you run into this problem cap off the vent line to the tank and install a regular fuel pump with only one line in and one line out to the carb and your troubles will be gone!