The fuel pick up in the stock tanks are 5/16" along with 5/16" lines feeding up the frame rail to the engine compartment. 5/16" are stock for most fuel injected engines as well so you should be fine with that size pickup and lines. Stock CJ with carburetors are obviously low pressure systems so a high pressure pump will have to be installed.
The issue you might run into, which is the same one I have been looking at lately, is that the stock return line from the engine to the tank is 1/4". Going from 5/16" feed to 1/4" return may cause some back pressure or pressure spikes in the fuel rails. Even if you step up the line to 5/16" for the return, which is what I did, it is still a 1/4" line at the sending unit where it feeds back into the tank. I figured 6" of 1/4" would be less restrictive then the entire 10' worth of return line at 1/4". I should note that I actually swapped the 1/4" fuel return line with the 5/16" vapor canister feed line since they are both already in the right place. So the vapor canister feed line is now the 1/4" line. I figured that was ok since the nipple from the valve that feeds the vapor to the canister is also 1/4".
I've got a Mustang engine and stock Mustang supply and feed lines are 5/16". The tech support at the company who makes my fuel pump also suggested I step up to the 5/16" return line. But there is still that 6" worth of 1/4" right at the sending unit at the tank. Anyone know of a sending unit that fit into a CJ tank that has 5/16" supply and return hook ups?
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1979 CJ7, FI 5.0L Ford, NP435, D300, Full floated D44 Detroit, D30 Detroit EZ Locker.