Gas Disappears Outta Monojet - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**NewBayColony** · 12-20-2025, 10:42 AM

Can't figure this one out. If I drive the truck (72 Chevrolet 292) and park it for an hour, I have to crank and crank until the fuel pump fills the bowl again. Then it starts up. If the bowl is full, it's starts right right up like it's supposed to.
I have rebuilt the carb and I was wondering if I replaced the check ball with the wrong one. I do have an inline fuel filter between the pump and carb. The truck runs fine but it's kind of embarrassing when I go to start it. Thanks in advance.

**kwmech** · 12-20-2025, 01:25 PM

Check the gas cap and see if it is vented. Another thing, is there a paper filter in the carb inlet? If so get the one with the check valve

Just thought of this--- drive it around for awhile then pull over and loosen the gas cap and see if you get a sucking sound. Shouldn't, being a 72 with a cannister, but we'll see

**Rust_never_sleeps** · 12-20-2025, 04:08 PM

Give it a listen and see if fuel is draining into the manifold, I think you'd hear it boiling

If you suspect it's draining back, you could squirt some dye(or ATF?) in the bowl and see if you get color in your inline filter

**NewBayColony** · 12-20-2025, 08:26 PM

Quote:

Originally Posted by kwmech

Check the gas cap and see if it is vented. Another thing, is there a paper filter in the carb inlet? If so get the one with the check valve

Just thought of this--- drive it around for awhile then pull over and loosen the gas cap and see if you get a sucking sound. Shouldn't, being a 72 with a cannister, but we'll see

I should have mentioned that it's a 3/4 ton so I have no emission systems, no cannister.

**NewBayColony** · 12-20-2025, 08:27 PM

Quote:

Originally Posted by Rust_never_sleeps

Give it a listen and see if fuel is draining into the manifold, I think you'd hear it boiling

If you suspect it's draining back, you could squirt some dye(or ATF?) in the bowl and see if you get color in your inline filter

I like the die idea. Thanks.

12-20-2025, 10:42 AM	#1
NewBayColony Senior Member Join Date: Mar 2017 Location: Northbridge,MA Posts: 515	Gas Disappears Outta Monojet Can't figure this one out. If I drive the truck (72 Chevrolet 292) and park it for an hour, I have to crank and crank until the fuel pump fills the bowl again. Then it starts up. If the bowl is full, it's starts right right up like it's supposed to. I have rebuilt the carb and I was wondering if I replaced the check ball with the wrong one. I do have an inline fuel filter between the pump and carb. The truck runs fine but it's kind of embarrassing when I go to start it. Thanks in advance. __________________ 72 C20 292 3OTT 77 GMC 2500 4x4 Longstepper 350 4sp 50 3100 ex Airforce/Town of Mendon fire truck 72 GMC 1500 2wd short stepside 250 4sp 78 GMC 2500 4x Longstepper 292 4sp 54 6400 Chevy 5 window 4 sp 2sp vac rear end Shell oil truck/dump truck (Norman)

12-20-2025, 01:25 PM	#2
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,941	Re: Gas Disappears Outta Monojet Check the gas cap and see if it is vented. Another thing, is there a paper filter in the carb inlet? If so get the one with the check valve Just thought of this--- drive it around for awhile then pull over and loosen the gas cap and see if you get a sucking sound. Shouldn't, being a 72 with a cannister, but we'll see Last edited by kwmech; 12-20-2025 at 01:37 PM.

12-20-2025, 04:08 PM	#3
Rust_never_sleeps Senior Member Join Date: Jun 2022 Location: San Ramon,CA Posts: 1,070	Re: Gas Disappears Outta Monojet Give it a listen and see if fuel is draining into the manifold, I think you'd hear it boiling If you suspect it's draining back, you could squirt some dye(or ATF?) in the bowl and see if you get color in your inline filter __________________ 1970 C10 Custom longbed 350/350 “Carburetors are forgiving, timing is not” — Thunderhead289

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