Gas tank pressure?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

kc69 · 10-13-2009, 03:52 PM

Trying to get my 68' chevy sb 350 started, and it just cranks over and over. It ran for about a minute or two and then died. I then heard a hissing noise coming from my gas tank lid (pressure). Do you think my fuel pump is out, or could it be a clogged fuel sending unit screen, or something else. oh, and just put in a new fuel filter in the 2 barrel rochester.

**John Fabris** · 10-13-2009, 04:02 PM

Sounds like your tank is plugged. What is happening is as you crank your engine, your fuel pump is pulling fuel out of the tank, creating a vacumn. As your engine runs, the vacumn in tank becomes too great and fuel pump is no longer pulling fuel due to the increase vacumn.

Replace your gas cap with a vented gas cap and it should work. Note to test this, take your gas cap off and then start your engine. I willing to bet that it does not die this time.

cdowns · 10-13-2009, 04:19 PM

you probally have the wrong gascap for that year you should b running a vented cap// as far as starting did you set points plugs etc those things need to b done for a motor to run

kc69 · 10-13-2009, 05:09 PM

faulty sending unit. It showed I had a 1/4 tank of gas, when I was actually bone dry. The gasket around the fuel inlet was torn, so will replace it since I pulled it out. The cranking apparently built up pressure inside the empty gas tank..

10-13-2009, 03:52 PM	#1
kc69 Registered User Join Date: Sep 2009 Location: Kansas city, Mo. Posts: 28	Gas tank pressure?? Trying to get my 68' chevy sb 350 started, and it just cranks over and over. It ran for about a minute or two and then died. I then heard a hissing noise coming from my gas tank lid (pressure). Do you think my fuel pump is out, or could it be a clogged fuel sending unit screen, or something else. oh, and just put in a new fuel filter in the 2 barrel rochester.

10-13-2009, 04:02 PM	#2
John Fabris TOTY 2006 Join Date: Dec 1999 Location: Magalia CA USA Posts: 2,270	Re: Gas tank pressure?? Sounds like your tank is plugged. What is happening is as you crank your engine, your fuel pump is pulling fuel out of the tank, creating a vacumn. As your engine runs, the vacumn in tank becomes too great and fuel pump is no longer pulling fuel due to the increase vacumn. Replace your gas cap with a vented gas cap and it should work. Note to test this, take your gas cap off and then start your engine. I willing to bet that it does not die this time. __________________ John Fabris 67 C10 SWB

10-13-2009, 04:19 PM	#3
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Gas tank pressure?? you probally have the wrong gascap for that year you should b running a vented cap// as far as starting did you set points plugs etc those things need to b done for a motor to run __________________ 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

10-13-2009, 05:09 PM	#4
kc69 Registered User Join Date: Sep 2009 Location: Kansas city, Mo. Posts: 28	Re: Gas tank pressure?? faulty sending unit. It showed I had a 1/4 tank of gas, when I was actually bone dry. The gasket around the fuel inlet was torn, so will replace it since I pulled it out. The cranking apparently built up pressure inside the empty gas tank..

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