Two Gas Tank Question

When I got my CJ it had an electric fuel pump and an electric valve operating one tank under the seat and one in the rear. When I put it back together I put a stock fuel pump on the motor and just hooked up the under seat tank. One fuel line goes to the fuel pick up and one to the return line. Now I would like to hook up the back tank also. I got a new electric switch but I'm not sure how to plumb it. If I just plumb the rear gas tank into the circuit and I switch to the back tank it looks like it will pump fuel into the under seat tank ala the return line. Once the under seat tank gets full I'm not sure what it will do. Has anyone played this game?

 

Gregg I'm not sure I understand you, but if you use a T or a splitter valve you will feed off the selected tank.
You need to run the feed lines for both tanks into the splitter and then to the carb.

 

Yes, but what about the return line? There is a fuel line from both tanks but a return line from the mechanical pump only to the under seat. I suspect that the electric fuel pump has an internal pressure switch and sends fuel to the carb on demand while the mechanical pump uses the return line to bleed off any extra fuel. I still have the electric pump but even if I use that what do I do with the return line? Just plug it at the under seat tank? I'm hoping to make sense here but it is kind of hard to describe if you haven't set up twin tanks. I used to have twin tanks on a 78 Cherokee and both tanks had return lines so the fuel filled the front tank and then dumpted excess into the rear. I have a feeling I need to drop the back tank and see what fittings it has on top if any. The fuel outlet on the rear tank is at the bottom front and just gravity feeds into the line.
Thanks all,

 

Ah ok I got you know.
May need to look into a t on the return line as well.
The only twin tanks I've had were on diesels.

 

get a pump without the return line.

JB

 

I have the electric with no return line but can I just cap the return on the under seat tank? Does it need a vent?

 

yes you can plug it, the cap is vented. You can also get a mechanical pump without the return.

JB

 

Thanks. Does anyone have a part number for an unvented pump? Was it stock for some year I can order?

 

Gregg-

I would consider splitting the return line as well if the rear tank has a port for it. I wish I had a return line with mine. You're at the stage now where you may be able to...

Food for thought.

 

Thanks Dennis,
I sounds like the next step is to drop the tank out and take a look. I agree two return lines makes the most sense. This is a homemade square tank and if nothing else I should be able to put a return in the filler neck.
Another thing I've thought of to just put the electric on the line from the rear tank and tee it into the return line for the underseat tank. Flip a switch and transfer gas from the rear to the underseat.

 

Greg,

I tried capping my return line once and it was a disaster. You may want to think twice about getting rid of it.

Mike

 

Thanks Mike. I am leaning toward putting a return on the rear tank also.
Gregg

 

I have the same problem, except I have a mechanical valve. If I drive on the tank without the return line the return starts to fill the other tank, so I have to empty it first. I have seen electric valves that have return lines so it switches the main line and the return at the same time.

 

That makes sense. I think that is how my old cherokee was. I can live with that I think.