20 gal. fuel tank (gauge calibration?)

[manitou]

OK...I purchased an '83 CJ5 that is 95% stock original. I live in KC, and the Jeep is currently in AZ. I went out this past weekend to finally see/drive it--before having it delivered to KC in a couple of weeks. (my wife didn't want to risk driving it back. I sort of agree). Anyway, while we were out there, I learned that the Jeep was equipped with the optional 20 gallon gas tank. However, the gas gauge is calibrated for the original 15 gallon tank. I love the extra 5 gallons, but would like to know if there is a solution to the gauge issue. I do plan to replace the speedo assembly at some point, as it reads about 10mph slower than actual speed. Since the fuel gauge is integrated into the speedo assembly...I'd like to calibrate at that time. Thanks for any advice you all can share.

 

[rufus1138]

first place i would look is the sending unit, i would want to confirm that the float goes all the way to the bottom of the tank, also if this is the case then you could modify the arm to take advantage of the full swing of the tank capacity since the fuel gauge is just a proportional instrument, its not like we're running a totalizer system like aircraft do.

 

[manitou]

Thanks rufus1138. I'll certainly check the sending unit. I should note that it may be that the float is not rising all the way to the top, however. After filling up, the gauge held above the full mark for about 100 miles. Some might consider this to be a fortunate circumstance. But for me...it just means that, while having a 20-gallon tank--once the gauge drops below the full mark, I have to read it from a 15-gallon perspective. Thanks again, and have a great day!

 

[rufus1138]

i would suspect ur right, need to mock up a way to let the float travel that extra distance up and still not bottom out early.

 

[ThisGuyUKnow]

I think that the fuel gauge is the same part regardless of tank, the sending units are different, but if I remember correctly the 15 gallon sending unit won't fit the opening. You could try a replacement sending unit and see if it fixes the problem

 

[Only in a Jeep CJ]

Yes, gauges are the same. Sending units are different. The sending units are notorious for going out or not reading correctly. Try a new sending unit and go from there. You can also cycle it while its hooked up to confirm and check the gauge. An ohm meter will help too.

 

[Hedgehog]

manitou - I must say this, if your gauges are stock and they are working, keep'em. Replacement guages ae available, but they are terrible and won't last, that is unless you are prepared to spend $500.00 or so for GPS units. If your speedometer is a nice consistent 10 mph off you are in good shape. Half the battle is getting a consistent reading. There is a place up in Phoenix that will make up custom guage back grounds. IT would be possible to make one up that reads correctly for you. No trouble, just slap on a new set of numbers and you are golden. The other option is to change out your speedometer gear in your Transfer Case .