Gas Gauge works but not correctly

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Joined
Feb 19, 2010
Messages
97
Location
Nashville, TN
Okay, did search found interesting threads but no definitive answer.

Basically, this is what is happening..

When my tank is full, the gas gauge shows that it is full. It will continually show full (like all the way past the full mark) even after I've burned up a third of a tank. Then the gauge will start to move. It goes down rapidly from full to empty while I burn the second third of a tank and then it just sits on or past empty while I burn the last third of a tank.

It's like this:

Gas Usage............l--------,--------,--------l
Gauge Reading......................l--------l

It's the stock gauge.

Any ideas?
 
I don't have any ideas, but I can tell you that is similar to the way my 1972 FJ40 gas gauge worked from the day I bought it brand new right up to today. First half of the tank takes it down to the full line, the next third takes it to the half a tank line and I get exactly 50 miles from the half a tank line to dead empty. I thought that's the way all the old gas gauges worked. I'm not sure I could get used to a gauge that actually read correctly after 39 years of getting used to this one. I'll be curious to see if there's a fix.
 
the gauge work on résistance.... so mine is broke at middle. Full is Full line, empty is at the middle. maybe it's can help you.

the tanks is not build like full is full, middle is middle en empty is empty... this is somewhere like kayaker said. the tank is full at start, but the midlle to the empty is faster.
 
By the way it's realy cheap to change the level of the tank. maybe start with that
 
I have the same issue. I know my gauge is good, and my sender is new, and well grounded. My FJ is a '71, but I don't know if the cluster is original to the truck, and I bought the sender for a '71. Does anyone know if there was a change in gauges or senders at some point? i.e. old style sender not matching up with newer gauge?
 
The sender and the gauge have to match resistance for them to work correctly together. I had similar issues.....OEM sender, aftermarket AutoMeter gauges.....fuel level NEVER read correctly. Learned the hard way about the resistance. Now I have a new Auto Meter gauge that is 0 ohms = Empty and 90 ohms = Full with a sender that uses the same resistance (got the sender from Summit Racing). Gauge works fine now. Good luck with your fix. :cheers:
 
Had a similar problem with my 77 and replaced the sending unit and still had the same problem. Statered looking into the gauge cluster and found out that the previous owner had damaged the copper tape on circuit panel and tried to bridge the tape with solder.

Dave
 
not sure if this will give you any ideas...

On mine, the gauge wasn't working at all so I started with the sender unit. Pulled it out and checked for smooth movement and the correct ohm readings. It checked out fine. I previously had saved this info from Mud...


"===Fuel gauge sender info.
Here's the deal; 9/72 and older gauges/senders work this way:

110 ohms empty
3 ohms full
and with a 7 volt drop built into the sender (a full 12 volts will instantly burn out the gauge).

9/72 and newer gauges/senders work on
120 ohms empty
17 ohms full
and do work on a full 12 volts.

Most (not all) aftermarket gauges work on 240 ohms empty, and 33 ohms full."


It turns out my gauged was sprung from a P.O. installing the wrong sender unit in the aux tank. So I dissasembled the gauge cluster and was able to "calibrate" :D the gauge by carefully tweaking the bi-metal spring assembly so that the pointer was exactly on "empty" with the fuel sender float bottomed out. I did this because I think knowing exactly how empty the tank is is much more important that knowing exactly how full it is.

So now Empty on the gauge agreed with empty on the sender but I found I had a couple of gallons left in the tank at that point. So I bent the senders float down until bottom of the sender's range meant no more gas. Sooooo, now, empty on the gauge REALLY means empty in the tank.

My gauge now stays pegged on full for the first quarter tank and then drops from there.
So maybe pull the sender from your tank and check its operation and ohm range.

Hope this might help a little....
B.
 
Last edited:
Thanks folks. I'll start by looking at the sender.

@BrianSanDiego, thanks a bunch for the ohm specs. That helps a lot.
 
Oh good, I wasn't sure if that would help or not. You're welcome and good luck.
B.
 
It's been a while since this thread was posted so I thought I'd add something new for the Cruiser owners who do a search on this topic in the future. Since I posted my reply almost two years ago, I've since removed my gas tank to paint it and the floor underneath. In the process, I inverted the tank a few times during the painting process. After I reinstalled it, the gas gage actually started working correctly. A full tank is right up to the full line on the gage, half tank is actually about 8 gal remaining and empty line is just that. Looks like manipulating the sender can work wonders on the way it reads. How's that for a cheap fix.
 
My 1972 gas gauge reads 2/3 when actually full and reads empty when there is 1/3 tank. I replaced the sender and the new sender reads identical. What is the best way to calibrate (adjust) the system? Bend the sender arm or is there a gauge adjustment to be made?
 
My 1972 gas gauge reads 2/3 when actually full and reads empty when there is 1/3 tank. I replaced the sender and the new sender reads identical. What is the best way to calibrate (adjust) the system? Bend the sender arm or is there a gauge adjustment to be made?

Checking in over a decade later with the same exact issue. Anyone know a fix or workaround for this?
 
Your odometer is the best gas gauge IMHO. Having an Aux tank is a good plan too. My 72's gauge reads F for a long time and E is actually empty. I did a Datsun B210 as my 12.5 gal aux tank. I bought an assortment of low value 2% resistors and was able to get my gauge to read 1/2 (F) to E when I flicked the installed gauge switch to read the aux tank.
 
If your tank is full and the gauge only shows 2/3 full, I would 1st pull the sender and ground it, hook up the sender wire and swing the arm and watch the gauge as it goes thru its motion. Make sure nothing is interfering with the sweep of the senders swing arm inside the tank. It could be installed incorrectly. You can check the resistance of the sender thru its sweep too. The FSM should have the resistance numbers for the sender. If the sender checks out, then I would look at the wire connections and then test the gauge. The FSM has info on testing the gauge. The empty reading could be the an adjustment, but with the full reading the float should be topped out when the tank is full. If it doesn't go to the top of the tank then it would sit on full for a while, like @charliemeyer007 mentioned. Being on full for a while is not really as much as an issue as knowing when its empty.
 
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