Plastic Fuel Tank

I replaced my fuel tank a few months ago with an MDS plastic. The old one was not in good shape, the PO had drilled holes in the top for an additional sending unit instead of replacing the other. I can't say I am happy with the tank, everytime I make a right turn, fuel leaks out between the cap and the filler tube, I purchased a new cap, thinking this was the issue. Nope, same problem, right turn, fuel out. The manufacturer stated that this was a problem with this style of Jeep, B.S. My other tank didn't leak from the fuel cap. Anyone else have issue with this? Starting to PMO!!!

 

I know that my '73 with the added under-seat tank would drip out the gas cap vent if there was liquid gas up against the cap. That was a steel tank from Jeep, and it was the vent in the Stant cap that was the problem, not the tank seal.

The tank has to seal as well as a steel tank if 1) the surface across the filler neck that the cap seals against is flat, and 2) the filler neck holds on to the cap as well as the steel tank, so that the seal is tight with the filler neck. If you still have the steel tank, you can measure these two characteristics and compare them to the plastic tank. If you can show MTS that the filler neck is distorted or somehow badly formed, they should help you.

 

Wasn't there a post the not long ago about vented and non vented fuel caps. Somebody posted the part numbers for both of them.

 

Maybe. You need a vented cap with this tank, regardless. It's not set up for vapor recovery, which is the only situation where you use a non-vented cap.

 

This is one of the annoying traits of the early Jeeps. I've never had a cap that didn't leak when the tank is full or nearly full. My underseat tank has a separate vent line with a rollover valve so I can get by without a vented cap. If I can find one. Maybe I can turn my vented cap into a non-vented cap with some silicone. I'm not exactly sure how the venting system on the cap functions.

 

I have a 65 CJ5 with metal tank that used to lead when full. I got a new cap from Walcks which cured the problem.

 

I always leave room under the cap for expansion, or unlevel ground. Mine will leak if too full or parked on a side hill. I bought a plastic tank, but sent it back, the filler neck was not centered in body hole, bought the steel tank instead.

 

I purchased the tank from Ray Buck and they said use the original cap which is a non-vented for my 70' with the dauntless. It leaked, so I purchased new one and same thing. I even called Ray Buck back and asked them about it, they called MTS and said this is normal. I'm going to try timgr's advice with a vented cap. I ordered it last night from summit. I may just re-weld my old tank and clean it out to use. I guess I'll know next week.

 

The charm of an early Jeep. Sucks to never put more then 6 gallons in a 10 gallon tank.

 

I had this problem with the cap that MTS supplied. On Patrick's advice, I got a cap from NAPA. It still leaked a bit. I then made a gasket from Buna-N material. It completely sealed it, even off road and during hard right turns.

 

My 65 has the origional under seat tank and cap and does not leak when full.

 

Maybe I just want to make things more difficult!

 

Update, replaced the cap(again) and still leaks. Made a call directly to MTS, the person I spoke to is going to talk to engineering to try and verify which type of cap, model " etc. Hopefully I can get this resolved soon.