gas tanks F100

[js818]

I am installing 1970 F100 non EEC tank into 1972 t hat had EEC. I will remove all EEC but I need vented gas cap for the non EEC. I think but don't know for sure that the filler necks are different and the caps are not interchangeable. Has anyone done this and can you offer any advice? Thanks

[fordman]

The necks are different in two ways. Length and cap fitting. The non eec tank needs the longer non eec neck. The eec tank uses a shorter filler neck. These necks that you want can be found on 67-69 f100 and f250. The f250 also had the non eec longer necks after 69. I dont remember what year f250 went to eec. I do know after 72 the in cab tanks were used in some 73-75 or 76 trucks. They can also be found in f500 and 600 trucks.

[js818]

Thanks Fordman! Great response to my question! LMC lists one filler pipe for 1967 through 1972. The filler neck can be made longer but the cap is the problem.

[fordman]

Yes there are two difderent caps though.

[js818]

Thanks again! I picked up a vented gas cap and it seems like the problem is the way it locks when turning on filler neck. I think if I modify the 1972 filler neck I could make the vented cap work on the 1972 filler neck. I will make the filler neck hose work between the tank and filler neck! When warm if needed I will start searching for new parts based on your previous reply.

[BobbyFord]

*delete

[js818]

Delete?

[Kurt Combs]

I have a 72 F250 with a non vented tank and I can't find a cap that doesn't leak gas on a hot day if the truck has a full tank and parked on a slope. It leaks when the cap is lower than the fuel level in the tank. If I had a vented tank, instead of a vented cap, I think this problem would go away, assuming I could get a cap the would seal tightly. I recommend you keep the old tank and put a fuel filter on the vent tube to keep dust out and avoid a vented cap. Just my worth....

[js818]

The option of keeping the old tank is gone. It was bad with rust, it sat for 18 years in a barn. It's not hilly were I live so that probably won't happen as much as me worrying about a rusty tank! The tank I got is spotless and for 30 bucks with the sending unit it was a deal for me. The filler neck modification took me 20 minutes and is done. How do you park at so that the cap is lower than the gas level?

[fordman]

Leaky caps can happen just parking on a sloping street when the tank is full. Or over full.

[BobbyFord]

Delete?

I posted some info that was already in the thread.

[js818]

Well surprise! I got everything back together and drove it for about 15 miles. Seemed like it ran good but I thought I heard a funny sound. I opened the hood and saw my fuel line bouncing around like crazy! Turns out my fuel pump was cracked and just hanging by the rod connecting the top and bottom............Try again tomm

20150221_183613_resized_1.jpg

[js818]

Another thought. If I left the EEC loop attached to the cab rear above tank and used the return line from it terminating into a inline filter or something else. Wouldn't the fuel system have worked properly?