Fuel Cap

My jeep has stalled twice for lack of fuel when the fuel tank was nearly full. Both times it restarted after about a minute or less. I decided it was caused by a vacuum in the fuel tank. Got home and remove that gas cap and found it was not vented. My question is where can I find a vented cap?

 

I don't believe the caps are vented. It could be a pump or carburetor issue. Does it immediately start back up after it stalls or do you have to wait a while?

 

Will it run with the cap loose?

 

Most if not all of the early under seat fuel tanks took a vented gas cap...............check your local Parts Stores or some of the early aftermarket Jeep suppliers.

 

Answers to some of the previous questions.

I have to let it set for a short while. Fuel pump and carb were new with rebuild. (4 months ago and a little over 400 miles) After it starts it will keep running for several miles. Fuel line does not have a filter, which I will add. I contacted Kaiser Willis and ask them if they have a vented cap-not answered yet.

 

Year/model/equipment? We can't help you without that information. Every technical question should describe the year and equipment of the Jeep somehow. Under driver's seat tank or tank in the rear?

Every cap for the under-seat tank that I've seen has been vented. There is no other provision for venting the under-seat tank. If you are in this forum, it is most likely that you have the under seat tank. But that's a guess based on the incomplete info you've given us.

The caps for the tank in the rear may be unvented. If so, they are intended to be vented by the factory vapor recovery system. If the vapor recovery is capped off, and you have a sealed cap, you either need to vent the tank or use a vented cap.

 

Like timgr mentioned it would help knowing what you have........I see in your profile that you have a 64 CJ and one can only assume that you still may have the under seat tank but who knows? As I mentioned the under seat does require an externally vented gas cap.........not an unusual Item!.......the other thing on the under seat tanks is that the fuel pickup is in the very bottom of the tank at the lowest point...........seems reasonable for 1940's technology applied in the early CJ's until our elders figured out that every spec of dirt , grime and rust that flakes off from the inside is going to get sucked down into that little 5/16" fuel line hole that's headed to your carb................Fuel filter "YES" ..............Flush your tank? Maybe? Check your float bowl needle & seat for dirt? YES!..........Put a filter on and during that process before you add the filter , lightly use some compressed air to blow back any debris that is in the line back to the tank..........or if it's near empty ...........drain it and take it off from both ends and blow out...........pay attention to what comes out as it will give you a good indication of the inside condition of the fuel tank.........if it's a rear mounted original tank then that has a different venting system as Tim mentioned above and should be treated in that manner.

 

I found a vented fuel cap at JC Whitney. P/N Stant 10625 On sale today with free shipping. Total Cost $12.25

More answers: Jeep is CJ5 with under seat tank. Tank was cleaned inside at rebuild, all lines are new, needs fuel filter which I will add this week. I believe the vented cap will solve the issue.

 

You can test this very easily... If it is the cap, it should run fine by simply leaving the existing cap loose.

If not, the problem is elsewhere. Definitely should add a filter and maybe back-blow the lines - especially since everything is "new."

 

I bought a vented aftermarket gas cap from walcks a while back for my 59 cj5 with under seat tank and hated it since day one it always sloshed fuel out all over paint and road and yard on side hill. made my jeep always stink like gas.

I then saw a NOS cap on ebay for like $17 and bought it and I love it all those other problems went away and it has inside like a ball check valve that relieves pressure when needed and keeps fuel from sloshing out. If I remember right the inside of the cap is stamped Eaton or something similar and has a cork gasket. I love this NOS cap

 

My 1971 CJ5 V6 has both a rear and under the seat tank. The caps are different sizes. Both are vented. The part numbers are:

Under seat tank: Stant: 10625, Napa: BK 7031020

Rear Tank: Stant: 10623, Napa BK 703122

 

Forget the J C Whitney cap. It is not vented. Packing List says vented, WEB site says it is vented. They did issue credit.