inaccurate gas gauge?

[sreilly77]

just filled my 98 grand cherokee today (which totally sucks with gas prices these days). i let the gauge go all the way down to E so i could put gas treatment in the tank (i usually don't let it get below 1/4). when i filled it up all the way, it took 15 gallons to fill the tank. i thought these tanks were 23 gallons (20 gallon with a 3 gallon reserve). i am guessing my gauge is inaccurate because the needle was right on top of E. i'm told that the sending unit on the fuel pump is starting to go bad and i just want to check with you guys to make sure that is what it is.

another thing that leads me to believe that it could be the sending unit is sometimes when it is very cold (it can get below 0 here sometimes) i let the jeep warm up for 5 minutes. say the gauge is at 3/4 of a tank when i first start it. when i come back out to drive off, the gauge moves up to the next line right before full. so basically i just need some clarification that the sending unit is my problem. thanks.

[dksob81]

I have the same problem in my 98 5.9Limited. Been having it for quite some time now. and then sometimes it will be on E and the GAS LIGHT will be on but it you let it sit for a few minutes it will work it's way up - sometimes to even a 1/4 tank or close to.

[sreilly77]

Originally Posted by dksob81

I have the same problem in my 98 5.9Limited. Been having it for quite some time now. and then sometimes it will be on E and the GAS LIGHT will be on but it you let it sit for a few minutes it will work it's way up - sometimes to even a 1/4 tank or close to.

yeah that is exactly what mine did today. before i got gas i went to wash it and i was looking for quarters and letting it idle with the light on and eventually the light went out and the needle moved up to the notch right before 1/4 of a tank. i guess it is a common problem with jeeps.

[dell520]

Mine does the same thing. I let it get to a quarter tank and fill up but it usually only needs 15 gallons. Is it an easy fix?

[sreilly77]

Originally Posted by dell520

Mine does the same thing. I let it get to a quarter tank and fill up but it usually only needs 15 gallons. Is it an easy fix?

From what I understand, the needle on the sending unit which is located on the fuel pump sometimes gets bent, sending an slightly incorrect reading to the fuel gauge on the dash. I'm told you can just replace the sending unit, but it makes more sense to just replace the entire fuel pump if you haven't yet to save you troubles in the future.

Now this is what I just thought of today also. The gas tank size in the ZJs (1993-1998 Grand Cherokees) is 23 gallons. I am going to assume that that 3 of those gallons are for the reserves. Therefore, if you filled up from 1/4 of a tank and it only took 15 gallons, that leaves 5 gallons left before the LOW FUEL light comes on. Then thats where you get your last three gallons of gas. So that would make more sense with the issues that we have been having. I mean there is even times that my LOW FUEL light comes on and the needle isn't even on E yet.

But no matter what, I still fill my tank once it gets down to 1/4 of a tank unless I am adding fuel system cleaner once a month, then I let it run down to E.