Carberator losing prime

Sam Barrett · November 2nd, 2009, 08:19 PM

If left setting over 3 days, I must prime the carberator to start the engine. It is a 1972 350 with a Quarajet.

Is this most likely a check valve in the fuel pump or in the carberator itself?

Erinyes · November 2nd, 2009, 10:27 PM

Are you certain there is no fuel in the bowl?

First thing I'd look at is the accelerator pump seal. If there is fuel in the bowl, but moving the throttle does not produce a twin squirt of fuel, it can be quite difficult to fire it up if it's been sitting any length of time.

An easy way to test it with the engine running is to let it idle, then use a screwdriver or something to depress the rod directly, without moving the throttle. The engine should die.

If it does not, rebuild it - kit and float, unless it is brass with no leaks.

zed · November 3rd, 2009, 05:52 AM

Common problem with Qjets.Fuel slowly leaks thru the cast plugs in the float chamber. Some coat them with epoxy when rebuilding to stop the leaking.

Olds64 · November 3rd, 2009, 06:36 AM

Zed is correct. You can coat the jet plugs on the bottom of the fuel bowl with epoxy to prevent them from leaking. This is a common problem with Q-jets.

Erinyes · November 3rd, 2009, 04:00 PM

Leaking plugs is a common problem, true, but checking the accelerator pump takes about ten seconds. It's still the first place I'd look. If the pump is shot, rebuilding is needed anyway, at which point coating the plugs is a no-brainer.

I'm still curious as to whether Sam has definitively determined the bowl is empty.

Sam Barrett · November 3rd, 2009, 08:25 PM

Yes the bowl is empty. So I must have a leak in the bowl. I am going to rebuild and I will let you all know the reults. Also, I am going to replace the fuel pump as well.

I just found out that the check valve for the fuel pump is in the fuel filter.

Olds64 · November 4th, 2009, 07:00 AM

Well, since you need to disassemble the carburetor to coat the bottom of the fuel bowl with epoxy you might as well rebuild it while you are at it.

Sam Barrett · November 4th, 2009, 07:46 AM

I have the rebuild kit and JB quick weld on my work bench.

Thanks for all of the help.

November 2nd, 2009, 08:19 PM	#1 (permalink)
Sam Barrett Nordic Blue 442 Join Date: Feb 2008 Location: Bronson, Florida Posts: 18	Carberator losing prime If left setting over 3 days, I must prime the carberator to start the engine. It is a 1972 350 with a Quarajet. Is this most likely a check valve in the fuel pump or in the carberator itself? __________________ Nordic Blue 442

November 2nd, 2009, 10:27 PM	#2 (permalink)
Erinyes Registered User Join Date: Aug 2009 Posts: 29	Are you certain there is no fuel in the bowl? First thing I'd look at is the accelerator pump seal. If there is fuel in the bowl, but moving the throttle does not produce a twin squirt of fuel, it can be quite difficult to fire it up if it's been sitting any length of time. An easy way to test it with the engine running is to let it idle, then use a screwdriver or something to depress the rod directly, without moving the throttle. The engine should die. If it does not, rebuild it - kit and float, unless it is brass with no leaks. __________________ Top executives at Blackwater Worldwide authorized secret payments of about $1 million to Iraqi officials that were intended to silence their criticism and buy their support after a September 2007 episode in which Blackwater security guards fatally shot 17 Iraqi civilians in Baghdad -- look over there! ACORN!!! "The amount of money that ACORN has received in the past 20 years altogether is roughly equal to what the taxpayer paid to Halliburton each day during the war in Iraq."

November 3rd, 2009, 06:36 AM	#4 (permalink)
Olds64 Landyacht Club President Join Date: Jul 2007 Location: Lawton, OK Posts: 4,286	Zed is correct. You can coat the jet plugs on the bottom of the fuel bowl with epoxy to prevent them from leaking. This is a common problem with Q-jets. __________________ Ferris, my father loves this car more than life itself... Apparently, you don't understand! Ferris, he never drives it! He just rubs it with a diaper! Cameron Frye Ferris Bueller's Day Off 1986

November 3rd, 2009, 04:00 PM	#5 (permalink)
Erinyes Registered User Join Date: Aug 2009 Posts: 29	Leaking plugs is a common problem, true, but checking the accelerator pump takes about ten seconds. It's still the first place I'd look. If the pump is shot, rebuilding is needed anyway, at which point coating the plugs is a no-brainer. I'm still curious as to whether Sam has definitively determined the bowl is empty. __________________ Top executives at Blackwater Worldwide authorized secret payments of about $1 million to Iraqi officials that were intended to silence their criticism and buy their support after a September 2007 episode in which Blackwater security guards fatally shot 17 Iraqi civilians in Baghdad -- look over there! ACORN!!! "The amount of money that ACORN has received in the past 20 years altogether is roughly equal to what the taxpayer paid to Halliburton each day during the war in Iraq."

November 3rd, 2009, 08:25 PM	#6 (permalink)
Sam Barrett Nordic Blue 442 Join Date: Feb 2008 Location: Bronson, Florida Posts: 18	Yes the bowl is empty. So I must have a leak in the bowl. I am going to rebuild and I will let you all know the reults. Also, I am going to replace the fuel pump as well. I just found out that the check valve for the fuel pump is in the fuel filter. __________________ Nordic Blue 442

November 3rd, 2009, 05:52 AM	#3 (permalink)
zed Registered User Join Date: Oct 2008 Location: Saskatchewan Prairies Baby! Posts: 142	Common problem with Qjets.Fuel slowly leaks thru the cast plugs in the float chamber. Some coat them with epoxy when rebuilding to stop the leaking.

November 4th, 2009, 07:00 AM	#7 (permalink)
Olds64 Landyacht Club President Join Date: Jul 2007 Location: Lawton, OK Posts: 4,286	Well, since you need to disassemble the carburetor to coat the bottom of the fuel bowl with epoxy you might as well rebuild it while you are at it. __________________ Ferris, my father loves this car more than life itself... Apparently, you don't understand! Ferris, he never drives it! He just rubs it with a diaper! Cameron Frye Ferris Bueller's Day Off 1986

November 4th, 2009, 07:46 AM	#8 (permalink)
Sam Barrett Nordic Blue 442 Join Date: Feb 2008 Location: Bronson, Florida Posts: 18	I have the rebuild kit and JB quick weld on my work bench. Thanks for all of the help. __________________ Nordic Blue 442

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