anyway to test a fuel pump - The 1947 - Present Chevrolet & GMC Truck Message Board Network

*vegaschevy* · 09-30-2009, 10:25 PM

how do i know my fuel pump is actually bad? anyway to test it?

Just curious

**lolife99** · 09-30-2009, 10:30 PM

Is this a new pump or an old one?
They are cheap,... I'd just replace it.

*vegaschevy* · 09-30-2009, 10:43 PM

Quote:

Originally Posted by lolife99

Is this a new pump or an old one?
They are cheap,... I'd just replace it.

am doing that, still would like to test it. Why not? no need to throw a part at an engine.

Is also like to go form a 3 line to a 2 line. Im guessing the return line is like a vapor line. pros and cons to doing that?

**Boog** · 09-30-2009, 10:54 PM

You can buy a fuel pressure test kit and plumb it in between the pump and carb and you'll know what it's putting out. They usually run less than $25 i think.

*vegaschevy* · 09-30-2009, 11:00 PM

Quote:

Originally Posted by Boog

You can buy a fuel pressure test kit and plumb it in between the pump and carb and you'll know what it's putting out. They usually run less than $25 i think.

thats not worth it../ HAHAHA

so anyone know what I can do as far as going from a 3 line to a 2 line fuel pump? the third line can it remain open?

mclairmo · 10-01-2009, 12:44 AM

Pull off the hose or hard line coming from the pump and insert into a glass jar and turn over the engine to verify if it is pumping fuel. You can go to the two line pump or plug third line. I believe it's just a return line.

*vegaschevy* · 10-01-2009, 12:48 AM

Quote:

Originally Posted by mclairmo

Pull off the hose or hard line coming from the pump and insert into a glass jar and turn over the engine to verify if it is pumping fuel. You can go to the two line pump or plug third line. I believe it's just a return line.

so if i go to a two line fuel pump i can just cap off the return line to the tank?

mclairmo · 10-01-2009, 01:01 AM

Yes, that's my understanding.

jojo · 10-01-2009, 01:16 AM

Yes you can just cap it.

The return line on my pick up was never connected either at the pump or the tank as long as I've had the truck. (basically there's an unused hard line strapped to the fuel supply line.)

I just put in a new pump but didn't realize it was 3 lines until I got it home. So I installed it anyways and capped off the return outlet.

cdowns · 10-01-2009, 06:27 AM

take off line to carb put in jar turn over engine for 15seconds the pump should pump about one pint

that's what it says in the factory service manuals which by the way are a great invstment on any vehicle

mclairmo · 10-01-2009, 05:16 PM

Quote:

Originally Posted by cdowns

take off line to carb put in jar turn over engine for 15seconds the pump should pump about one pint

that's what it says in the factory service manuals which by the way are a great invstment on any vehicle

That awesome info to know.

lofly'a · 10-01-2009, 11:42 PM

to answer your original question on how to test a mechanical fuel pump, go to a parts store and pick up a mechanical fuel pump tester/vacuum gauge. a good one will come with instructions on the procedure to test. to find out what your engine requires from the fuel pump you'll need the service manual specs for your engine (if your engine has been modified i don't have a clue as far as a reference, i'd guess by the carb specs.). i have all the Chilton and Motor Service manuals from the late 1950's til about 1980 courtesy of my dad so i had all the books growing up. a mechanical fuel pump is a simple lever type diaphram pump whose performance is measured by the mechanical stroke, diameter, and travel of that diaphragm, and it's performance is based on how much vacuum pressure it can produce. the one i have is made by Lisle and i bought it at Advanced auto parts. PM me is you need more info

09-30-2009, 10:25 PM	#1
vegaschevy Account Suspended Join Date: May 2009 Location: las vegas nv Posts: 1,493	anyway to test a fuel pump how do i know my fuel pump is actually bad? anyway to test it? Just curious

09-30-2009, 10:30 PM	#2
lolife99 67-72 parts collector,… Join Date: Nov 2002 Location: Mid-MO Posts: 22,691	Re: anyway to test a fuel pump Is this a new pump or an old one? They are cheap,... I'd just replace it. __________________ Keith Convert to disc brakes. http://67-72chevytrucks.com/vboard/s...d.php?t=444823

09-30-2009, 10:54 PM	#4
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,109	Re: anyway to test a fuel pump You can buy a fuel pressure test kit and plumb it in between the pump and carb and you'll know what it's putting out. They usually run less than $25 i think. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

10-01-2009, 12:44 AM	#6
mclairmo Registered User Join Date: Jan 2006 Location: Take Off Posts: 1,908	Re: anyway to test a fuel pump Pull off the hose or hard line coming from the pump and insert into a glass jar and turn over the engine to verify if it is pumping fuel. You can go to the two line pump or plug third line. I believe it's just a return line.

10-01-2009, 01:01 AM	#8
mclairmo Registered User Join Date: Jan 2006 Location: Take Off Posts: 1,908	Re: anyway to test a fuel pump Yes, that's my understanding.

10-01-2009, 01:16 AM	#9
jojo printing is my trade Join Date: May 2009 Location: San Antonio, Texas Posts: 349	Re: anyway to test a fuel pump Yes you can just cap it. The return line on my pick up was never connected either at the pump or the tank as long as I've had the truck. (basically there's an unused hard line strapped to the fuel supply line.) I just put in a new pump but didn't realize it was 3 lines until I got it home. So I installed it anyways and capped off the return outlet. __________________ Jojo's '70 stepside build thread: http://67-72chevytrucks.com/vboard/s...d.php?t=344184

10-01-2009, 06:27 AM	#10
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: anyway to test a fuel pump take off line to carb put in jar turn over engine for 15seconds the pump should pump about one pint that's what it says in the factory service manuals which by the way are a great invstment on any vehicle __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

10-01-2009, 11:42 PM	#12
lofly'a Registered User Join Date: May 2000 Location: Alexandria, LA 71301 Posts: 1,451	Re: anyway to test a fuel pump to answer your original question on how to test a mechanical fuel pump, go to a parts store and pick up a mechanical fuel pump tester/vacuum gauge. a good one will come with instructions on the procedure to test. to find out what your engine requires from the fuel pump you'll need the service manual specs for your engine (if your engine has been modified i don't have a clue as far as a reference, i'd guess by the carb specs.). i have all the Chilton and Motor Service manuals from the late 1950's til about 1980 courtesy of my dad so i had all the books growing up. a mechanical fuel pump is a simple lever type diaphram pump whose performance is measured by the mechanical stroke, diameter, and travel of that diaphragm, and it's performance is based on how much vacuum pressure it can produce. the one i have is made by Lisle and i bought it at Advanced auto parts. PM me is you need more info __________________ -02 avalanche (daily driver) -66 gto ragtop 389/400 (garage queen, hand-me-down from dad) -72 Tribute Trans Am (6.0LS/T56 6-speed) in progress -2003 YUKON (Wife's) -71 gmc swb fleet (current project, gonna shave everything, bags, stuff w/ 20's, gen III powertrain) -48 3100 SWB - 12/31/23 LONG TERM Project Last edited by lofly'a; 10-02-2009 at 08:30 PM.



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