88 MJ gas tank

tugalo · Jan 14, 2007

good morning guys,

I have an 88 MJ long wheel base with the 16 gal gas tank....on a Dodge Dakota forum, I saw a write up that asserted that the optional 23 gallon tanks and the 16 gallon tanks were the same, the only difference being the length of the filler neck. does anyone know if this is true and / or how to fix it.
The only info I have seen on increasing tank capacity was the write up about raising the air vent tube inside the tank.
thanks........tugalo

thall · Jan 14, 2007

simple calculations can confirm that a 23 gallon tank will be physically larger than a 16 gallon tank...

where is these assertive people go to school???

or........

that is one L O N G F I L L E R N E C K

and what is there to fix????????

Samman · Jan 14, 2007

where is these assertive people go to school???

Same place you went

old_man · Jan 14, 2007

There are two different stated capacities of XJ tanks. The difference is indeed the filler neck. The part you didn't realize is that the filler neck projects into the tank further on the 16 gallon model. Besides going further into the tank, it goes downward. This prevents putting as much fuel in the tank. In otherwords, the 16 gallon tank ends up with a lot more air in the top. By pulling out the filler tube and shortening it, you can increase the capacity. Now, all that said, I have no idea if this holds true on the MJ tank.

A search should yield the instructions on how to modify the tanks.

Comanchedude · Jan 16, 2007

tugalo said:
good morning guys,

....on a Dodge Dakota forum, ( first mistake)

I can tell you as a Comanche owner that has actually replaced bad fuel tank that they are different size and the larger tank is just that, it is longer so it will not fit in the short bed.
(The Comanche tank filler tube does not protrude down into the tank)
As for filler necks controlling thank capacity,
Well I would have to ask first why they would use that to adjust take capacity. If you design a fuel tank to hold a specific amount of fuel safely then that would seem to be what and engineer would set that capacity at. And not add a longer than needed filler tube to reduce the capacity of the take they just designed.
Now you may find that someone figured out they could add capacity beyond the design of a tank by defeating the methods used to control said capacity, but that does not mean it is a safe practice?
“The later is just my opinion”

thall · Jan 16, 2007

I have a longbed with a new tank ready for install.... and it was necessary to choose the capacity....and the application was wheelbase specific... and I have not looked down in it to see the filler depth...

I agree with comanchedude ..... and still stand by my statement of calculated volume...

and the XJ tank is different than the MJ tank under discussion.

ren · Jan 17, 2007

So is the #&%@$ skid plate for the MJ (anyone interested in a SERIOUSLY hacked up XJ skid, by the way?). I figured that out the "experimenting" way. Oh, and you can add a second tank to the MJ, but it goes on the other side, and your exhaust will be REALLLLY close, so I think that it is now time to go find a smaller tank for a spare now.

thall · Jan 17, 2007

I took my skid off years ago... it was what caused the leak in the bottom of my tank initially... and left it off... now years later, the JB Weld repair on the tank is failing, and I have a new 23gal tank ready for the install.

not sure if i will put my skid back on..... probably can't find the bolts anyway

23 gal should be enough.....

.

lawsoncl · Jan 19, 2007

This was common in the YJs in the early 90s. The 15 gallon tank was really a 20 gallon tank with an extended fuel vent line. It took me about 1/2-hour to remove the vent line and pull out the 7" plastic extension on mine. After that I could put in 20 gallons, but the gauge read full for the first 6 gallons. I don't think this was done in the XJs or MJs, though.

88 MJ gas tank

tugalo

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thall

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Samman

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old_man

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Comanchedude

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thall

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ren

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thall

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lawsoncl

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