Gas guage incorrect reading

[Lugnut]

78 CJ-7 gas guage reads wrong. When tank is full, guage reads 3/4 full. From there, as I use up the gas the guage drops off sharply, dropping from 3/4 down to 1/3, then to empty. When guage reads empty I can only get about 6 gals into tank. I replaced the gas tank about 4 years ago and the sending unit about 3 years ago when the old one went bad. It all worked ok for about a year then started giving bad readings. I just replaced the fuel guage(actually the entire speedometer head with a new one) and it reads about the same as the old guage. I've checked the electrical connections on top of the tank, cleaned the ground-wire connection from the tank to the frame, run a ground-wire from the dash to the body and a wire from the body to the frame. I really don't wanna pull that dang gas tank back off again. Any ideas?

[SAR-4800]

Whoa, talk about timing... and location!

I was driving my '88 Grand Wagoneer just last night and ran out of gas. I haven't had this Jeep but only a week and certainly didn't know that it's empty when reading 1/4 tank. Fortunatly, a passerby gave me a lift to the gas station and everything turned out ok. I was happy that it wasn't a mechanical failure, as that was my original thought.


As for location, I live in Hendersonville, NC... practically right down the road. Hey, better come see the Apple Festival while you still can. LOL

[J20fan]

I have the same problem, I fill the tank and it only reads 3/4. Once I get to about 1/8 it drops off quick but I still have enough fuel to go for a while. Instead of pulling the tank I always carry a 5 gallon jerry can in case my guesstimate is off.

[79 FSJ]

The float in the tank is either getting stuck, or is loaded with fuel, meaning that the device has soaked in some fuel and not floating at the top of the tank...

Hope this helps, it is a common problem with the old Mustangs...

Dave

[Careful34]

EXACT same thing happened to me as happened to SAR, except I was lucky enough to run out in front of a gas station and had an empty gas can with me! Fills up OK but once it gets to 1/4 tank it stops going down. Good time to fill back up anyway!

[porchpiggy]

My 88GW reads full, drops fast to 1/4, then takes forever to get to empty, which fortunatly is really empty. I think a gauge that reads correctly is a phenomenon in an FSJ. :cool:

[JB]

If Im not mistaken you didnt have to pull the tank off to begin with.. there is a hole the size of a softball on your floor board to access your gas tanks electrical wiring ..

[JB]

OH , my bad, you were talking about a CJ, I was quick in assuming that you were talking about a wagon.. It is the wagoneers that have the access hole in the floor board for the gas tanks electrical wires on the sending unit....

[ September 03, 2001: Message edited by: JB ]

[wagdriver]

I believe if you check previous posts you will find that the gas gauges are grossly inaccurate on Wagoneers and other FSJs. I know from experience that mine is very non-linear. Mine at fill-up never reads completly full. I have a 23 mile round trip to work, the first two days I use a half a tank according to the gauge, then it takes about seven days to run the rest out. I try not to let it get too low. One thing for sure if the yellow light comes on you best find a gas station. ;)

[<Texico>]

Yes WagDriver,
That's not your gas gauge, that's our patented new gas with "non-linear action" formula to prolong the gas after using the first half tank. You see, our competition doesn't offer that, now do they? :D

[wagdriver]

So that what it is redface.gif LOL I thought it was a plot to get me to by gas more often. But being old and slow it didn't sink in. Ah! the joys of FSJ ownership :D :D :D

[Dan]

What is the gas tank capacity in an 86 GW? I just fill mine up every couple of hundred miles.

[wagdriver]

If I am not mistaken the tank capacity on most Wagoneers is 20.3 I have not heard of anything larger than this from the factory. Our chief info man Bob Barry may know something more about this than I do. But I have never heard of anything else.

[wagdriver]

If I am not mistaken the tank capacity on most Wagoneers is 20.3 I have not heard of anything larger than this from the factory. Our chief info man Bob Barry may know something more about this than I do. But I have never heard of anything else.

[Dive 30]

according to my TSM and my Chilton's the Grand Wagoneer 84-86 was 20.3.

[2j20's]

Mine dose the same thing got tired of that real fast so i added a aux/tank ;) Great for the long halls.....

[Dan]

Funny. The same day that I posted a reply (yesterday), I ran out of gas 2 blocks from a gas station with the wife in the car. I got an earful. I guess I missed my 200 mile mark!

[Darin]

2j20s,

how easy was the aux tank install. anything you could share on how feasible tht would be on a 89 GW?

[jasonthomasfrance]

Hello,

I'm the proud owner of a 1976 Waggie. And my gas gauge does not work at all...

Are most of everyone's gauge problems with the actual sending unit in the tank, and not the gauge? If so, how can that be fixed? New sending unit? Newer tank/fuel cell?

I'd like to know how far my new Waggie will go without running completely out of gas.

[wagdriver]

Access to the sending unit is under the rear driver side seat. There should be a round cover under the carpet. It may be riveted in, drill out he rivets and you will have access to ever thing there. Check all the wire going to the level sensor. If all is good there then the gage wiring is suspect. If you can get you hands on a Haynes manual(50029) they have a good check out procedure there. If the access panel is not there, dropping the tank is the only option to get at the stuff you need to get at.

[ September 09, 2001: Message edited by: wagdriver ]

[joe]

<BLOCKQUOTE>quote:</font><HR>Originally posted by wagdriver:
Access to the sending unit is under the rear driver side seat. There should be a round cover under the carpet. <HR></BLOCKQUOTE>
Unfortunately that's not going to work for Jason's rig(76) The access cover is only on 80 and later Wags/Cheros. Jason's gonna have to drop the tank to get at his sending unit.

[jasonthomasfrance]

Arrghhh!! If it's not one thing, it's another! Maybe I'll make myself an access cover... Has anyone tried that? Without pucturing the tank beneath?

[wagdriver]

Thanks -joe, I did not know when they started puting the access panel in that is why I added the last part to my reply ;)

[mechanic58]

This has been my experience with gas gauges: MOST gas gauges have a resistor on the back of the gauge itself, somewhere on the back of your speedo cluster. This resistor burns up over time and ultimately causes the gas gauge to read incorrectly. My 89' wag has the very same problem right now and I have not yet begun to trouble shoot it, but if I were a bettin man, I'd say I'm going to find a burned resistor on the back of my gauge cluster. Almost all of the older GM vehicles (60's,70's and 80's) had the same problem. You can find these resistors on the "HELP" rack at your local Advance or Autozone, they're univerial for the most part and only cost about $3. Only problem is, most gauge clusters are a ***** to get out. LOL. Hope this helps. :D