1971 Challenger Gas Cap Question

Posted By: JAK

1971 Challenger Gas Cap Question - 05/10/12 09:20 PM

Should my 71 challenger gas cap be Vented/Anti-Surge or Pressure/Vacuum?

I have a gas tank with the four vent lines and the cap that is on there now is a Non-Vented cap that when I open releases a lot of pressure.
Thanks

Posted By: Challenger 1

Re: 1971 Challenger Gas Cap Question - 05/10/12 09:36 PM

Pressure vaccum, if the car is running right don't worry about the pressure. Means your fuel system is tight, imo.
I get pressure sometimes depending on the temperture and both my cars are vented just like the factory vented them.

A vented fuel cap will leak down the side of a challenger. I'm sure lot's of guys here have done it and it's not pretty.

71 factory service manual.

74 FSM.

Posted By: Mr D21

Re: 1971 Challenger Gas Cap Question - 05/12/12 02:46 PM

pressure vacuum & non-vented are the same,,,

Posted By: Steve340

Re: 1971 Challenger Gas Cap Question - 05/23/12 05:22 AM

If you have the 4 tube tank system, you should not have any pressure build up. If you do, then your vent line going to the engine is plugged or pinched. My 70 Duster with that system (California car w/ECS) had the same problem and when I took off the vent line at the crankcase breather, it was plugged up.

Posted By: JAK

Re: 1971 Challenger Gas Cap Question - 05/24/12 01:09 PM

I will have to check that line.

Thanks for the info everyone

Posted By: Challenger 1

Re: 1971 Challenger Gas Cap Question - 05/24/12 11:12 PM

Quote:

If you have the 4 tube tank system, you should not have any pressure build up. If you do, then your vent line going to the engine is plugged or pinched. My 70 Duster with that system (California car w/ECS) had the same problem and when I took off the vent line at the crankcase breather, it was plugged up.

It is normal to have pressure in the tank some days.
Depending on a lot of things, a 1/4 pound of pressure will seem like alot when you open the cap. The cap will hold up to pound of pressure.
The system is a vapor saver system, it's not meant to constantly to be vented to the atmosphere where you would have no pressure in the tank at all times.
I'm not talking about 1970 models

I understand how it's goes togeather and plumbed on each year car. My 71 car is a N-95 car and it is exactly like it was when new, even the stuff on the firewall and speedo sending unit.

Posted By: JAK

Re: 1971 Challenger Gas Cap Question - 05/25/12 02:07 AM

My car too is a N95 car, unfortunately I am missing most of the system. All i have left is the ambient temp sensor and bracket on firewall.

Posted By: JAK

Re: 1971 Challenger Gas Cap Question - 05/29/12 04:50 PM

Quote:

If you have the 4 tube tank system, you should not have any pressure build up. If you do, then your vent line going to the engine is plugged or pinched. My 70 Duster with that system (California car w/ECS) had the same problem and when I took off the vent line at the crankcase breather, it was plugged up.

My hard metal line was plugged when I removed the rubber hose going to the crankcase breather.