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Joined: Jun 2017
Posts: 412
Backyard Mechanic
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OP
Backyard Mechanic
Joined: Jun 2017
Posts: 412 |
Gas cap for 32 car should be vented?
1932 Chev 5 Window Coupe
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Joined: Jan 2002
Posts: 30,701 Likes: 141
ChatMaster - 25,000
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ChatMaster - 25,000
Joined: Jan 2002
Posts: 30,701 Likes: 141 |
Gene Schneider
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Joined: Apr 2010
Posts: 734 Likes: 14
Oil Can Mechanic
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Oil Can Mechanic
Joined: Apr 2010
Posts: 734 Likes: 14 |
Hello Bertus,
Capping a gas tank air tight will quickly starve the fuel pump and carb and will shut down engine for lack of fuel even though you know you have a full tank of fuel. If air cannot enter, a vacuum is created and holds fuel from flowing out of tank. Gas caps have spring loaded valves in them to allow air to enter tank as fuel level drops, thus avoiding a vacuum. Some caps have visible air holes while others are hidden from view. I broke down in an 18-wheeler shortly after polishing the twin aluminum saddle tanks. Aluminum polish uses up a lot of cloth/paper towels to wipe away, but not if you use flour to dust the polish first. Then it wipes away quickly and the tanks are bright and shiny. Problem was, one fuel tank cap with exposed vent hole got plugged with floured polish. Both tank lines tee together and fuel level should drop equally. Not this time. As engine started to fail, it was quickly pull to the side of the highway and shut it down. Don't starve diesel injectors. Fuel tank slap check revealed one tank empty and the other full. Had to use my belt as a strap wrench to unscrew the cap against the vacuum. Talk about a sucking sound as the cap finally unscrewed. Used a tooth pick to clear the vent hole and down the road I went.
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Joined: Jun 2017
Posts: 412
Backyard Mechanic
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OP
Backyard Mechanic
Joined: Jun 2017
Posts: 412 |
Bought a new gas cap from FS. Underside has a yellow plastic center with some small holes but it is not vented as far as I can tell. (Thought it was.) Getting close to the end of my restoration and went for a short test drive. It ran fine. Removed the gas cap several days later and there was a considerable vacuum sound. Guess I need to check around for the proper cap.
Thanks.
1932 Chev 5 Window Coupe
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Joined: Nov 2002
Posts: 7,472 Likes: 26
ChatMaster - 7,000
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ChatMaster - 7,000
Joined: Nov 2002
Posts: 7,472 Likes: 26 |
If it were mine I would call the FS and get some answers. My cap came from them and has been on for 20 + Years with no problems.
Last edited by m006840; 07/21/23 09:06 AM.
Steve D
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