Fuel cap

I was just reading a thread about fuel cap leakage and it mentioned having a vent for the fuel tank. Ive had a problem lately with fuel leaking out of my rear tank filler cap and today i took off the cap and fuel shot out like it had built up pressure. My tank is pretty full but i never noticed this problem before. I have put a new lockable cap on but i dont see any kind of vents on this or my old cap. I did however lately have a leaking hose going to the filler that was all cracked and old, so i replaced it. I was thinking maybe having cracks in the old one was letting out any pressure and now its new it cant get out anymore. I didnt even know i had to have a vent, how important is it? Ive also been having starting problems when warm lately, starts fine cold but if i leave it to sit for 10 mins it wont start again, dont suppose there's any connection? Im a girl and will admit im pretty dumb when it comes to cars, but i really love this jeep and so want to learn!

 

you may need to have a vented cap . i have a 68 and it leaks gas
too but it has to have the vented cap . when it's warm you may try taking off the cap and see if it will start.

 

Yeah, there are two basic kinds of caps - vented and non-vented. You may have trouble finding a vented cap, since modern cars use a vapor recovery system to vent the fuel tank. This prevents the gasoline fumes from polluting the atmosphere.

Your fuel tank needs a vent of some kind. From the picture in your avatar, your fuel filler neck looks different from what I would expect on a 1970 Jeep in the USA. A better picture of the filler would be helpful. Did your Jeep originally have a fuel tank under the driver's seat?

 

View attachment 15772

 

Well i never thought of that, i always thought the closed off hole was for a light that had been removed later. Ill take some better pics tomorrow, and ill ask about a vented cap where i got my other one, but im worried they only have modern ones. Is there any danger not having one that vents?

 

when i cant find a vented fuel cap,itake a very small screwdriver and disable the vent by tearing up the valve or messing up the spring.i make sure it is done by putting it to my mouth and blowing and sucking thru small hole were the vent is located.ive done it on my 62 jeep truck and my 67 cj5.works great.

 

I also have this problem. My tank is definately not vented. I know when I'm empty because I can hear the tank oil-canning beneath me . I will have exactly 30 feet before the engine cuts off.

I was thinking of drilling a port on the filler neck and routing some tubing up the rollbar and adding a small filter. That way when the jeep is submerged, less water will allow itself to go in the tank.

 

that will work i did that to my 68 today works good

 

Just be sure to put a rollover valve in the end of the line so liquid can't escape.

 

Well today i put back my original cap back on. Dont know if its vented but its not such a tight fit as the new one, its pretty loose. I drove for 20 mins then stopped for 10mins or so and would you believe it, it started straight away! Am i right to think its probably been making it flood, and if so would my spark plugs have been getting wet? They are only a few weeks old and pretty expensive because they are military waterproof ones, could i have damaged them? should i take them out and give them a clean? Now i need to find a cap that locks but still vents, i have a photo of my old one, its 1 1/2 (3.8cm) inches across on the inside ring. Anyone know if i can get one this size that locks? So glad i read about this in this forum or i would never of guessed that this was the cause of my starting problems, probably would have replaced all sorts that i didnt have to! View attachment 15779

 

Mmm. Probably the opposite problem - not enough fuel. If the tank is sealed, the fuel pump can only pull so much fuel out until the vacuum in the tank equals its suction. Then you run out of fuel until you break the vacuum by removing the fuel cap (or until you wait for the vacuum in the tank to slowly leak down).

I would not worry about the plugs.

One of the Jeep suppliers in the States should be able to ship a locking cap to you. Lynn mentioned Walcks above - look at the 'favorite sellers' forum for some other good sources.

 

I had similar problems. When I got my Jeep there wasn't a cap on it. I bought what was considered the stock replacement cap for it and when drove the Jeep it would run fine for a few minutes and die..........then almost immediately start back up.
I ended up drilling a hole in the cap and haven't had the problem since.