Fuel tank replacement options.

[Gnmtl72]

79 J10 360 Idaho

Truck has a secondary fuel tank in the bed/toolbox, and previous owner said she never used/didn’t work? the main tank. I would prefer to get the fuel tank out of the bed and back underneath if I can. Im currently working on dropping the fuel tank right now to check if it’s leaking or ok to use. Rusty bolts and nuts are making this a slower process but Im chipping away at it.

In the meantime I am trying to do a little bit of research in the case that I do have to replace or rebuild the fuel system. Is there an aftermarket brand that is ok to use? Is there some that are good to avoid? Is it better to actually modify the tank? I believe I have seen posts where people have used squarebody chevs tanks in place if where the spare tire would go. Truck doesn’t actually have a spare, but I would like one, are there any other popular upgrades for tanks?

[seventynine]

https://bjsoffroad.com/polyethylene-fue ... nt-filler/

You probably don’t have many options for a stock replacement. I think all or most of the poly tanks are made by MTS. I doubt you could get a new steel tank at this point.

There are two versions…one with the fill and vent tubes in the front and one with the fill and vent tubes on the side.

https://www.mtscompany.com/j-truck.htm

[Yeller]

Many of us are running the poly replacement tank from MTS. It fits, and IMO poly is superior to steel, never rusts and deforms if impacted rather than denting.

[tgreese]

A '79 should have a steel tank. The simplest approach would be to remove the original tank and repair/refurbish it. This can include flushing, coating and soldering, as needed. You can do this yourself, or old-time radiator shops that actually repair radiators typically do this kind of work.

MTS shows a couple of different styles of tank for '79, with either side-fill or front-fill, and a few more styles of filler hose. The parts book shows one picture for '74-79 and lists only one tank for a '78-79 Townside (contradicting what the MTS website shows). I assume your truck is a Townside model and not a Thriftside (step-side). http://www.mtscompany.com/J-truck.htm

These trucks came with a gas tank skid plate optional, which addresses the impact question to some degree.

As Yeller points out, MTS is the sole source today for these tanks AFAIK, and only in plastic. No one is making replacement steel tanks. These trucks do not have much aftermarket support, compared to other marques. Same for the filler hoses. If you find other sources, they are selling the MTS parts.

To install a tank in the rear, AFAIK there are no suppliers for application-specific auxiliary tanks for these trucks. However, there is plenty of room in the spare tire area for a second tank - my J20 came to me with a second tank mounted there that holds about 20 gallons. You could use a custom fit tank, or adapt a tank from another application. Search old posts here and at IFSJA for more discussion.
https://www.bing.com/search?q=site%3Aif ... y+gas+tank
https://www.bing.com/search?q=site%3Afs ... y+gas+tank
Try different search terms and you'll find lots of coverage in old posts.