Fuel Gauge reading lower than it should

[erasedhammer]

So today I was driving home with between 1/4 and 1/2 a tank left, then a minute later I look back and see it has dropped to below a 1/4 tank (this was all on a flat road with no acceleration/stopping).

I thought this was weird so I went to a gas station to top it off. Filled it up, 15 gallons, I was able to physically see the fuel level, definitely completely full.

Checked the gauge was it was reading only 3/4 of a tank.
What could have gone wrong? Is the sender crapping out?

 

[fsearls92]

Typical military fuel gauge unfortunately

 

[erasedhammer]

Typical military fuel gauge unfortunately

No kiddin... is it the gauge or the sender?

 

[BLK HMMWV]

Most likely the sender. If it's the original it a cork float.

 

[erasedhammer]

Most likely the sender. If it's the original it a cork float.

Any tests I can do to find out?

 

[fsearls92]

On my m35a2 I replaced the sender and the float with no change in accuracy. Every mv I have owned has been this way too. Maybe HMMWV's are different, but just expect to learn how the gauge reads not as it reads.

 

[erasedhammer]

On my m35a2 I replace the sender and the float with no change in accuracy. Every mv I have owned has been this way too. Maybe HMMWV's are different but just expect to learn how the gauge reads not as it reads.

I would accept that, only my gauge was working perfectly for almost a year now and now it's decided to go crazy on me.

 

[Mario]

I'm having similar issue.
When tank is empty (as in dry) the gauge faces 9 O'clock (below empty).
I just filled her up and she only reads 1/2 full.

I know on my Tahoe, I could open the instrument cluster and remove the needle to set it to proper level.
Do I have that option on my M998 or is there a calibration/offset nub/dial that can be adjusted?

 

[pjwest03]

Frequently the sender. If you ground the gauge input it will read below empty. If you just disconnect the gauge input it will read full. Most often it's the float not floating.

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