Dual tanks and fuel injection

Hey ya'll, I was working on installing the fuel lines on my rebuild this evening and I had a thought...

I have two tanks in my CJ5, one under the seat and the other in the back. There's a tank switch valve between the two seats.

I planning on switching over to a fuel injection system like a Howell TBI and as such I'm running two lines from the fuel tanks.

So my thought was, how do you do run a return line to the proper tank when you use a manual tank switch valve.

Has anyone done this multi-tank conversion with success? Got pictures of your tank switch setup?

Appreciate all the help!

 

I would just run a single line from the underseat tank to the rear tank.

And then plumb only the rear tank for the FI.

That way, when the rear tank runs low, you open the valve and let the underseat tank drain into the rear tank.

 

I think in order for that to work the plumbing going to the rear tank will have to be large enough to allow a fast flow...in addition, the under seat tank will need to be vented in some way to allow air to come in while it drains into the other tank, otherwise the flow will be restricted due to the back suction. I don't know...it might work. How do dual tank setups normally work? I have one on my F150 but I've never gotten under there to figure it all out.

 

I expect that if you use a single external EFI fuel pump like the E-150 pump in this article http://www.binderplanet.com/forums/showthread.php?p=318149#post318149 you can just take gas from the tank you select. You'd also have to return gas to the tank you had selected... otherwise you would be filling one tank while you're draining the other. That would be bad. I presume there are dual-path valves available.

 

6 port valve,
http://www.pplmotorhomes.com/parts/rv-converters/motor-driven-fuel-tank-selector-valve-92-8999.htm

otherwise you could have 2 three way valves, one for feed and one for return, and make sure you switch them together.

 

Really easy with an external pump-----just "T" into the line feeding the pump, between the tank selector valve, and the pump.

Return fuel will go through the pump, or back into whichever tank is selected, as the fuel flow demand warrants.

With internal pump, the above will not work.

 

Your just asking for vapor lock with this setup. Fuel from the return needs to go to the tank, to deaerate and to cool off. Plus it would be next too impossible to prime this system.

 

Why?

Wouldn't the line between the pump and the injectors would still be pressurized?

 

the caps on the underseat fuel tanks are not sealed very well, and do allow air in. And most of em dont do a very good job of keeping fuel in either.

 

Yes, but the lines after the regulator would not be. Any vapor in those lines would feed back into the pump. In a regular system they return harmlessly to the tank.