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Gas cap
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Glassnose Aficionado
Supporting Member of Barthmobile.com 2/09
Picture of Danny Z
posted
This should be an easy one. On my 78 454 powered Barth, the gas cap is unvented and when I stop for gas there will be a significant amount of pressure to release when I remove the cap. Is this normal or should I have a vented cap?


79 Barth Classic
 
Posts: 3475 | Location: Venice Fl. | Member Since: 07-12-2004Reply With QuoteReport This Post
Official Barth Junkie
Supporting Member of Barthmobile.com 1/24
Picture of Steve VW
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Good question. The very early vehicles had vented gas caps. Later models (like my 86 Regal) had one way sealed caps which allowed air in but no fumes out. These had a suction line from the tank running forward to some hefty carbon filters in the front right wheel well, to collect fuel vapors which were then sucked into the carb and burned.

I'm not sure exactly when they switched caps and vent designs. I think it was around 1980. When in doubt, the vented cap will always work. (By now the carbon filters are probably not working anyway.)

We have 3 inches of snow... Overcast and 23. head bang Time to head back to Florida! Cool


9708-M0037-37MM-01
"98" Monarch 37
Spartan MM, 6 spd Allison
Cummins 8.3 325+ hp
 
Posts: 5149 | Location: Kalkaska, MI | Member Since: 02-04-2011Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 8/11
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Good morning you guys! I second Steve VW’s reply. If you ever experience a vacuum though that’s an indication of a vent failure in the cap and it will starve the engine of fuel. Happy Trails!


Billy & Helen Thibodeaux

Retired from Billy Thibodeaux's Premiere RV, Inc. Scott, LA 70583 I-10 Exit 97
The Farm is near Duson, LA I-10 Exit 92 then N 1 mile on right
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billynhelen@me.com
Data Tag: 9404-3908-36XI-2C
1994 Sovereign 36' Widebody on Spartan IC (Mountain Master Lite) Chassis.
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Posts: 373 | Location: 1mile north of I-10 Exit 92, Duson, LA USA in The Heart of CAJUN COUNRTY ! ! ! | Member Since: 05-14-2005Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 3/23
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My dad told a story on one of his brothers, a motorcycle enthusiast. Seems he thought the chrome cap for cycles tank was an improvement over the family's car gas cap. Grandad didn't get too far before the engine quit. The fuel pump pulled a vacuum, dimpled the tank against the baffles. I don't know the rest of the story but I think the original cap went back.
 
Posts: 1065 | Location: St. Charles, MO, USA | Member Since: 10-09-2003Reply With QuoteReport This Post
Official Barth Junkie
Supporting Member of Barthmobile.com 1/24
Picture of Steve VW
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How things have changed. Nowdays we get a Check Engine light and a P0455 or P0457 error code to tell us the gas cap is leaking! ROTFLMAO


9708-M0037-37MM-01
"98" Monarch 37
Spartan MM, 6 spd Allison
Cummins 8.3 325+ hp
 
Posts: 5149 | Location: Kalkaska, MI | Member Since: 02-04-2011Reply With QuoteReport This Post
Glassnose Aficionado
Supporting Member of Barthmobile.com 2/09
Picture of Danny Z
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On mine the buildup is pressure, not vacuum. When I stop after a long drive the pressure escapes when I take the cap off, often with embarrassing audio results.


79 Barth Classic
 
Posts: 3475 | Location: Venice Fl. | Member Since: 07-12-2004Reply With QuoteReport This Post
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quote:
buildup is pressure

That seems like the EVAP system has an issue....
Matt
 
Posts: 519 | Location: Massachusetts | Member Since: 07-28-2006Reply With QuoteReport This Post
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