Pressure building up in my gas tank - Chevelle Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 10 (permalink) Old Dec 8th, 01, 1:08 PM Thread Starter
 
Join Date: Jul 1999
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Hi. I have owned my 1968 el camino for over 14 years. Through all the 14 years I have owned it, I've had some kinda pressure building up in the gas tank. I want to get this problem fixed but just don't know what to do. I bought a new gas cap a few weeks back and that didn't do a thing. Even sometimes when I'm driving, I can smell a very strong feums and then when I stop my el camino turn off the engine and go and open the gas cap, a LOT of air releases. But shortly the pressure will just builds up again. Anyone know a solution to fixing this problem? I would appreciate any suggestions that I could do to resolve this. Thanks!
Michael

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Michael Minery
Orange, California
1968 Malibu El Camino
<A HREF="http://www.angelfire.com/ca/mineryhomepage/1968elcamino.html" TARGET=_blank>My 1968 El
Camino page</A>
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post #2 of 10 (permalink) Old Dec 8th, 01, 5:05 PM
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Do you have a charcoal cannister? These will fail occasionally and produce that strong fuel odor you're smelling. When the charcoal breaks up and the cannister becomes saturated with fuel, it prevents proper tank ventilation.
Also, I believe you can get both vented and unvented gas caps. You need to determine which one you need and make sure you have the right one. I think vented caps are used with fuel systems that have no vapor cannister.
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post #3 of 10 (permalink) Old Dec 8th, 01, 6:46 PM Thread Starter
 
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Ok, thanks for the reply. I have no canister on my 68 el camino. In fact I don't think it even came with one from the factory? I'll look into the vented gas caps. Thanks
<BLOCKQUOTE>quote:</font><HR>Originally posted by Randy Mosier:
Do you have a charcoal cannister? These will fail occasionally and produce that strong fuel odor you're smelling. When the charcoal breaks up and the cannister becomes saturated with fuel, it prevents proper tank ventilation.
Also, I believe you can get both vented and unvented gas caps. You need to determine which one you need and make sure you have the right one. I think vented caps are used with fuel systems that have no vapor cannister.
<HR></BLOCKQUOTE>



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Michael Minery
Orange, California
1968 Malibu El Camino
<A HREF="http://www.angelfire.com/ca/mineryhomepage/1968elcamino.html" TARGET=_blank>My 1968 El
Camino page</A>
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post #4 of 10 (permalink) Old Dec 8th, 01, 8:06 PM
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Chris
 
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I'm not sure, but if 68 El Camino gas tanks are the same as 68 chevelle tanks, then look at the top front passenger side of the tank. On mine there were I think 2 vent hoses. One had a sort of filter thing on the end. Make sure that air can get through the vent lines, that should be where the pressure gets relieved. In the past, I've drilled a small hole in the gas cap the let off the pressure. I'm not sure if this is a good idea though!

chris
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post #5 of 10 (permalink) Old Dec 20th, 01, 10:19 AM
 
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My '68, has got two 8" flexible lines coming out of the top passenger side of the tank for venting. Yours should have the same and they may be deliberately blocked because if they're not routed just right or if they're old and brittle they will leak gas especially if you're driving hard. If you open these up you will eliminate the need for a vented cap.
The reason you have this problem is because as your fuel pump removes fuel from the tank, it has to be replaced with air, if it can't then it creates a vacuum which is what you hear when you loosen the cap.
Try checking for the hoses and go from there.
Let me know how this works out for you.
MIKE CRAWFORD is offline  
post #6 of 10 (permalink) Old Dec 20th, 01, 1:14 PM
 
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Just wanted to add to Mike's comments-

In some cases, the vaporization of the fuel outpaces the amount being drawn off by the fuel pump. Heat is a major factor as anyone who has left a closed gas can in a hot garage can attest to. And I noticed Micheal is from sunny CA...you lucky dog!

Either way, you need to address the venting issue with your fuel tank...
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post #7 of 10 (permalink) Old Dec 26th, 01, 12:31 AM
 
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I have the same problem on my 70 elcamino i posted it yesterday my vent hose was blocked off with a screw i removed it now gas comes out the vent hose??
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post #8 of 10 (permalink) Old Dec 26th, 01, 12:38 AM Thread Starter
 
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<BLOCKQUOTE>quote:</font><HR>Originally posted by Joester:
I have the same problem on my 70 elcamino i posted it yesterday my vent hose was blocked off with a screw i removed it now gas comes out the vent hose??<HR></BLOCKQUOTE>

There is no vent hose on my 68 el camino. I got underneith it the other day looked really hard as saw nothing. If there is a vent it would have to be in the top middle of the tank and I can't see in that area.

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Michael Minery
Orange, California
1968 Malibu El Camino
<A HREF="http://www.angelfire.com/ca/mineryhomepage/1968elcamino.html" TARGET=_blank>My 1968 El
Camino page</A>
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post #9 of 10 (permalink) Old Dec 26th, 01, 6:32 PM
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I have posted "My solution" to this before but nobody has said if I was correct or if I'm retarded. I drilled a tiny hole in my unvented cap in my 67 Cutlass, solved the air release noises when I open the cap. Would love to find a vented cap for this application but nobody seems to have one. Anyone know of any sources for a vented cap?
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post #10 of 10 (permalink) Old Dec 26th, 01, 6:56 PM Thread Starter
 
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I will do this but just haven't got around do doing it yet. When I do, I will post my results. Sounds like a good idea though...
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