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Fuel Tank Pressure When Removing Gas Cap? #471371
09/17/09 10:34 PM
09/17/09 10:34 PM
Joined: Jan 2003
Posts: 208
Middleboro,MA
J
Jopar Offline OP
enthusiast
Jopar  Offline OP
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J

Joined: Jan 2003
Posts: 208
Middleboro,MA
I have 71 Plymouth and this car has an unusual amount of pressure when removing the cap. I will crack the cap for a couple of seconds prior to removing and after that I fully open it has a slightly shaken Soda/Pop bottle pressure release. Is this normal? Do I have the wrong fuel cap on the vehicle? Let me know your thoughts....

Re: Fuel Tank Pressure When Removing Gas Cap? [Re: Jopar] #471372
09/17/09 11:05 PM
09/17/09 11:05 PM
Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
DaytonaTurbo Offline
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DaytonaTurbo  Offline
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Posts: 21,318
Manitoba, Canada
You sure it's pressure when you open the cap and not suction? A 73 tank was installed into my 74 and because the venting system is different it looks like the guy who did it capped off the vent lines. That caused it to build suction inside the tank so I simply changed to a vented, locking gas cap and no issues since.

Re: Fuel Tank Pressure When Removing Gas Cap? [Re: DaytonaTurbo] #471373
09/18/09 07:26 PM
09/18/09 07:26 PM
Joined: Jan 2003
Posts: 208
Middleboro,MA
J
Jopar Offline OP
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Jopar  Offline OP
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Joined: Jan 2003
Posts: 208
Middleboro,MA
Yes, You are right it is suction... I will try a vented cap. Do you know if this problem will cause any adverse affects?

Re: Fuel Tank Pressure When Removing Gas Cap? [Re: Jopar] #471374
09/18/09 11:38 PM
09/18/09 11:38 PM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert Offline
Circle Track
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
I've had several vehicles way back that had that whoosh when you took off the cap (I assumed it was vacuum) & no starvation (but they were daily drivers not raced).


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Re: Fuel Tank Pressure When Removing Gas Cap? [Re: RapidRobert] #471375
09/19/09 08:38 AM
09/19/09 08:38 AM
Joined: Mar 2004
Posts: 531
SE Michigan
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farmington Offline
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farmington  Offline
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Joined: Mar 2004
Posts: 531
SE Michigan
You can also try to drill 1 or 2 small (1/8") holes in you cap. You shouldn't need much.

Re: Fuel Tank Pressure When Removing Gas Cap? [Re: farmington] #471376
09/19/09 10:50 AM
09/19/09 10:50 AM
Joined: Feb 2005
Posts: 4,884
Michigan
MNobody Offline
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MNobody  Offline
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Joined: Feb 2005
Posts: 4,884
Michigan
My buddy lost a couple pistons in his nitrous motor from fuel starvation, had a stock tank with a sump and the vent line was kinked. Pump couldn't push enough fuel, motor went lean, all done Mr. 351.







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