gas tank help

hey guys heres the problem,
i have a 1974 cj5 and the gas tank leaked. so i bought a new replacement steel tank from the 4wd catalog but i cannot get it to fit back in the rig. got to looking at at the old tank and it turns out threre is a lot more metal on the new tank around the mounting holes and on the out sides of the welds than on the old one. so i got out the grinder and went to work on the new tank. now it looks just like the old tank but it still won't fit. of course since i have painted the tank and used the grider on it i can't return it, so i have to make it fit. also checked the part numbers and it is the replacement tank for a 1974.
has anyone also encounter this problem? how'd ya fix it? please help.

thanks
b

 

Hmmm - very strange. Something has to be hitting somewhere. Are you able to see where the "seams" of the tank hit the frame, or somewhere that it's making contact to keep it from going in?

Also, are you working from under the Jeep, or do you have the tub off? I just re-installed the tank on a '74 that I have in the garage right now. It came out and went back in as easy as pie from the top... FWIW.

 

thanks for the reply. the body is not off the jeep and the jeep is not in the air. i was just under it with some jack stands.
anyway after several hours of banging, fabing and grinding the tank is in and not leaking.
the skid plate was just as tough and i ended up making new brackets to hold it on the front

took some measurments and the old tank and new tank differ by about one inch front to back and side to side. ??? i think the old tank is a 15 gallon and all i can figure is the new one may be a 16 gallon tank. buit in the catalog it says 1970-75 cj5 15 gallon steel tank. go figure.
i just hope i never have to touch it again.
thanks
z

 

I had the same problem with the same tank. Took a little work with the tin snips, but got it to fit. I just wasn't able to fit the original pad between the tank and shield back in.

 

I had a '73 that leaked. It developed pin holes in the bottom because the pad held water...I left it out when I replaced the tank. That pad soaked with gasoline has to be dangerous under a tank of gas

 

my tank didn't have a pad under it, it did have a small piece of foam on one of the corners but there was no room for it when i was done so i left it out.
i painted both the tank and the shield to prevent rust before the re-install.
i also have some spay-in bedliner stuff from the parts store i was thinking i would drop the shield and put a good coat of the liner on the bottom of the tank and all over the shield. the stuff isn't quite rhino or herc but it is very rubbery when dry. thought it could provide what ever protection the original pad provided. buti am not even sure it is necessary.

also the vent lines to the canister were capped off on my old tank so i capped them with a piece of hose on the new one. how important is the vapor canister? it took me a while to find it in the rear b/c it was completly covered with who knows what. i honestly thought it was part of the wheel well until i started looking for it. can these be cleaned up and reused or do i need a replacement? the second vapor canister is still at the front of the jeep but is alos not hooked up?
what should i do?
thanks
z

 

My intermediates ('73 & '75) both had the foam (?) pad from the factory. The '73 developed a leaky tank in a couple years, and this in dry southern California. I simply fiberglassed the bottom of that tank, and cured the problem.

The vapor canister should be under the hood, underneath the battery. The item you are looking at under the right rear fender should be the liquid check valve. If the vapor recovery system is there, there's no need to remove it. It requires minimal maintenance (clean the filter on the botom of the canister occasionally) and both vents the tank and recovers fuel vapors. Basically the charcoal in the canister absorbs vapors from the fuel tank when the engine is off. The vapor goes past the liquid check valve to the vapor canister and goes from the top of the canister and out the bottom. When the engine is started, a slight vacuum is applied to the top of the canister and clean air is drawn in the bottom, carrying the fuel vapor trapped in the charcoal into the engine, where it is burned. The early (ca '72-3) vapor recovery systems are basically passive, with no moving parts other than the check valve. The canisters became more comples over the years, with active valving controlled by additional vacuum lines.

Having the check valve without the canister doesn't provide any useful functionality. You may as well cap the vents and use a vented cap. of course, you will vent fumes to the atmosphere and possibly leak fuel out of the cap when the tank is full and you're on a hill (or upside down). If you want to add the canister, there's no performance penalty for having the working system - just cleaner air and a sealed fuel system.

 

I'm glad this came up b/c I was wondering the same thing....

On the '74 I'm working on - it has the two red plastic lines coming from the tank to the "filter-thingy" in the wheel-well. From there, another red line runs up the drivers frame rail to a canister that is down below the master cylinder on the drivers side, between the inner fender and the firewall.

All of the pieces are there and in decent shape, so I plan to re-use them. Just wasn't sure why there were two different parts...