71 Cj5 With 3 Tanks But Only 1 Works

I just bought a 71 CJ 5 with 37,000 original miles on the V-6. I have three fuel tanks but can only get fuel out of one tank. When I disconnect the fuel connection at the drivers under seat tank and at the rear tank not a drop of gas comes out of the line. The passenger under seat tank works as designed. I am trying to remove the drivers side tank as well as the rear tank. On the drivers tank it seems there is something holding it from underneath. On the rear tank have not got that far as yet. Any tips or advice?

Dennis

 

Hi Dennis - welcome from Boston!

A '71 came with the rear tank from the factory, and if you have an under-seat tank on both sides, they were added by a previous owner. Can't really say why the tank won't come out, since whoever installed it did something custom to hold it in. You're just going to have to figure it out. Post pictures if you want to show us what you have.

This is the factory plumbing for a '72 rear tank, which is basically the same as a '71.



You need to trace through the plumbing and determine where the fuel stoppage is. The TSM for 1971 will help you. These can be found at RockAuto as paper or CD-ROM format. More Information for DETROIT IRON DCDC103 Don't bother with the Haynes or Chiltons manual - they are not very througough and full of errors - you want the factory manual.

Also, this topic has been covered before in the forums. Reading old posts will help you. Search this site for relevant treads using Google or Bing with "site:earlycj5.com <your search terms>".

 

Thank you for the tips and advice, bad start to be new and then step on toes. I will do more research. TY

 

Dennis, you might look through these threads - site:earlycj5.com rear fuel tank - Bing

Re removing the rear tank, I have done it a couple of times, and it's just a matter of removing the skid plate (if present), disconnecting the fill hoses, and unbolting the tank from the chassis. It's a bit of a struggle, since space is tight. But it can be done. The small-diameter vapor recovery hoses and fuel pickup/return hoses on top of the tank are often rotten after 40 years, preventing the pump from sucking fuel from the tank. There are only two ways to get at them - drop the tank or lift the body (or cut a hole in the body? usually not acceptable).

 

If your under seat tanks have the fuel pick-up tube coming from the top of the tanks then they will not free flow fuel until siphoning is started.

 

A 71 would have only a rear mounted tank . so why would you want to remove it . I would remove the other two tanks if your trail riding will not require them

 

I understood he wanted to remove it to fix it, not eliminate it. Maybe I misunderstood...

Having all that fuel capacity is a plus (11 + 11 + 14 gal is 36 gallons, not excessive) and the only downside is the smell and occasional drip from the vented caps on the under-seat tanks, and the loss of the tool box on the passenger side.

 

Dennis, I would think about making it as original first, that meaning work with the rear mounted tank first, and make it work. The other tanks were put in later I would think. The Jeep you have has all the good stuff on it, bigger brakes, better steering, more drivable. The earlier Jeeps, like mine are more like driving an antique, fun at low speed and not in any hurry. Welcome and Good luck.

 

Thank you all for the comments and thoughts. Here is my situation. There are three tanks, one under the two front seats and a rear tank. The original owner installed an electric fuel pump with a toggle switch to activate each. A complicated system that I am trying to get rid of but here is my problem, the Jeep has not been driven in two years and I want to drain the old gas out. When I disconnect the rubber fuel line from the connection at the rear tank and one of the front tanks, nothing comes out so I suspected a clog. I disconnected at the tank and still not a drop of gag but there is gas in the tank and no debris or sediment. Driving me crazy LOL but this old Jeep with less than 40K original miles deserves to be restored and I will get it !! I appreciate all the advice please please keep it coming.

Dennis

 

I am guessing you haven't tried to install a electric pump to the hose coming from tank and just running wires to battery , as stated before the tanks will not gravity feed unless you get the fuel moving first . I gave up on sucking on gas hoses long ago . to get them started . one other thing have you tried blowing air in gas line to listen to see if there is any fuel in tank

 

A MityVac also works well to get gas flowing. Good tool to have.

 

Have you followed the fuel lines exiting the tank(s) to see if they all go to a common diverter valve that needs to be turned to a specific position for each tank? That would explain why only one tank flows.
That is how I would plumb multiple tanks.
-Donny

 

You gents are awesome. In regard to them tanks, the stem comes off the bottom of each tank and not the top. I am going to try connecting the rear tank directly to the fuel pump and see what happens. I may be creating a problem that is not there in the first place. By isolating to one tank at a time through the fuel pump and then into a gas can I can drain out the old and know if the system works. Since I disconnected them all at the bottom and one produced gas by gravity I the other two would as well. OK, a project for this weekend !! Stay tuned LOL

 

I had a electric solenoid and proper switch for my tanks when I built mine. Worked perfect every time in the shop. Twice it failed me on the road and I had to crawl under and swap hoses around. After the second time, I changed to the valve shown above and have had zero problems.

 

This is EXACTLY what I did. I do not trust the electric systems and it is in and connected to one of the gas tanks and works great. Still have to pull the other two tanks but at the end of the day I think I am going to go with just a rear tank and one side tank. This weekends project. TY for the tip

 

I agree Kyle and here in Lake Havasu the terrain is challenging so in field the simpler the better. Taking it down to have all the junk power washed off it now.

 

The final straw for me was.... 115 degree day laying on asphalt swapping the hose locations. Burnt half of my fore arm on the muffler, then gas ran down on to the fresh burn.

 

That is the animal and the schematic helps a lot, thank you for taking the time