dual fuel tanks

[johnnyreb]

I have always liked the look of the early CJ5 's with the underseat fuel tanks. And I have always like the idea of either an early with a late model rear tank of vise versa. So dad and i recently got an 80 CJ5 . Now I am on the quest to install an underseat tank. I know the early tanks were vented through the fuel cap.
Now comes the questions.
Mine has dual fuel lines coming out of the filter, does one return to the fuel tank and why?
Can I eliminate this extra line?
It's the first carburated engine with a line like that.
Will using the stock rear evap system with the earlier style cap vented tank make a difference?
I know it might seem odd, but it's an idea that took me 20 years to put into action.

 

[Torxhead]

That extra line to the fuel tank will relieve excess pressure in the fuel line. Excessive fuel pressure will blow fuel past the needle & seat in the carb and at least make the engine run rich, making it an emmissions thing, at least thats the way I see it. I have not heard of any problems from guys removing them.

 

[johnnyreb]

Thanks Torxhead. I just didn't see a need for it. Did older models contain it or was this a seventies emissions thing?

 

[Torxhead]

Looking at an online Morris catalog, it shows the dual outlet fuel filter for the '74-'90 AMC 258 i6 / 4.2l six.

 

[johnnyreb]

sounds like an EPA thing to lower emissions to me then.

 

[Kilo19]

doing some research here, and saw this...

did you end up getting an underseat tank?

Also, would it be possible to install (with modifications of course) an early underseat tank under the seat? or would fabbing one up be better, if so how much would be an average amount of fuel hold?

i'm looking at making some custom frames for the driver seat and thought about boxing in a tank and actually mount it under the tub, but the filler will come thru to the side, and mount right behind the door. with it under no vapor leaking will be inside, but i'll have a hatch/latch type thing to gain access to pump, etc....

hope this makes sense.

thanks.

 

[johnnyreb]

Kilo19
No I haven't gottn to the underseat tank, but it's on my list. Dad and I have discussed it at length since he used to own a CJ3b . He seems to think it should slide under the stock seat brackets with no problem. I just need to get the plate that bolts to the body and and allows the filler need to come through and remain recessed.
A stock underseat fuel tank is 11 gal.

 

[Kilo19]

when you get to that point i'd like to def read up on it. i like the thought of a few extra gallons of gas. been reading about some chevy electronic switches. just trying to wrap my head around how the gauges would work.

flip a switch on the fuel tanks, but do both tanks get wired to the gauge?

i'll cross tha bridge when i come to it

thanks

 

[TroyaCantrell]

I replaced my under seat with a new steel tank and it didn't have the second inlet for the return so I replaced the filter with a single outlet one and just eliminated the return line. I made a new hard line and replaced all the rubber in the engine compartment too. Still need to make a couple new hard lines for the engine but haven't started that process yet.

Mine does seem to run rich like Torx said but I don't know that it was caused by this change. I didn't have enough run time on the rig before the change to know for sure.

 

[johnnyreb]

I have a transfer switch lying at the house. both sending units run to it and when you swith tanks it switches sending unit. That switch is designed for a non return system as I was gonna put it on an old ford truck. they also make a switch with ports for return lines. I got mine at jcwhitney.
I'm betting the older fuel pumps had an internal relief valve in the diapharm. I seem to recall my 65 falcon had one and it would open when the fuel presure was maxed out.