Building pressure in gas tank?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

TugOwar · 03-01-2005, 02:52 PM

77 Chevy 1/2 ton 350/th350. All stock save exhaust from manifolds back.

This morning I'm driving to work and it starts cutting out at higher rpm. Got worse and worse until I finally had to stop and the engine died. I found the 3/8 rubber gas hose from the fuel line to the fuel pump was dry rotted and spraying gas.

So I think it must be sucking air and thats why its cutting out. But why is it spraying gas out when the motor is off... I loosened the gas cap and a big rush or air/fumes comes out. Strange but oh well..

Called the wife to come get me, gathered tools etc and replaced the hose. Fired it back up and start for home, it runs good until it heats up and then starts the same cutting out again, like its either loosing fire or starving for gas. I pulled over and loosened the gas cap and again it has pressure built up, I left the cap loose to see if that was the problem but it still cutting out if I try to give it much gas, idles fine though.

I limped it on home, closed the gas cap and let it idle for about 5 minutes and then checked and it has built up pressure in the tank again, wtf??

I don't know if the cutting out and gas tank pressure are related or which is the problem and which is a symptom...

I'm going to replace the fuel filter in the carb and spray the carb with some cleaner and see what happens. In the meantime I would appreciate any ideas you guys might have. This has me stumped.

BTW, I can't find any other gas leaks or shorted wires and the fuel pump is only a couple months old.

Jonboy · 03-01-2005, 04:51 PM

it's possible the vent line may be clogged. That's where I would start.

*1FaastC10* · 03-01-2005, 06:27 PM

change your gas cap. they're vented specifically for this purpose. either you've got a non-vented cap, or your vent is bad.

NeCrOmAnCeR · 03-01-2005, 08:17 PM

Correct me if I'm wrong, but that truck should have come with a evap canister which would prevent pressure build up. I agree with 1FastC10 about the vented cap, but unless the evap can has been removed and the corresponding hose plugged, this should not happen. Does your fuel pump have a return line? May also want to check the pump volume/pressure to make sure it is not bad (even though it is new)

03-01-2005, 02:52 PM	#1
TugOwar Registered User Join Date: Sep 2004 Location: Pleasanton, TX Posts: 1,723	Building pressure in gas tank?? 77 Chevy 1/2 ton 350/th350. All stock save exhaust from manifolds back. This morning I'm driving to work and it starts cutting out at higher rpm. Got worse and worse until I finally had to stop and the engine died. I found the 3/8 rubber gas hose from the fuel line to the fuel pump was dry rotted and spraying gas. So I think it must be sucking air and thats why its cutting out. But why is it spraying gas out when the motor is off... I loosened the gas cap and a big rush or air/fumes comes out. Strange but oh well.. Called the wife to come get me, gathered tools etc and replaced the hose. Fired it back up and start for home, it runs good until it heats up and then starts the same cutting out again, like its either loosing fire or starving for gas. I pulled over and loosened the gas cap and again it has pressure built up, I left the cap loose to see if that was the problem but it still cutting out if I try to give it much gas, idles fine though. I limped it on home, closed the gas cap and let it idle for about 5 minutes and then checked and it has built up pressure in the tank again, wtf?? I don't know if the cutting out and gas tank pressure are related or which is the problem and which is a symptom... I'm going to replace the fuel filter in the carb and spray the carb with some cleaner and see what happens. In the meantime I would appreciate any ideas you guys might have. This has me stumped. BTW, I can't find any other gas leaks or shorted wires and the fuel pump is only a couple months old.

03-01-2005, 04:51 PM	#2
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	it's possible the vent line may be clogged. That's where I would start. __________________ 1974 Jimmy- 5.3/4L80e/NP241

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03-01-2005, 06:27 PM	#3
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,399	change your gas cap. they're vented specifically for this purpose. either you've got a non-vented cap, or your vent is bad.

03-01-2005, 08:17 PM	#4
NeCrOmAnCeR Registered User Join Date: Feb 2004 Location: Hodgenville, Ky Posts: 735	Correct me if I'm wrong, but that truck should have come with a evap canister which would prevent pressure build up. I agree with 1FastC10 about the vented cap, but unless the evap can has been removed and the corresponding hose plugged, this should not happen. Does your fuel pump have a return line? May also want to check the pump volume/pressure to make sure it is not bad (even though it is new)



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