Gas gauge reading lower than it should

ab-buff

ab-buff

Joined
Mar 10, 2025
Messages
22
Age
72
Location
Tracy California
Bike
2004 ST1300
Hi
I didn’t do any searching for any threads on this subject sorry, but I had my gas tank off for probably a month. I completely changed the injection system and hoses and all kinds of things trying to get rid of the FI code for a knock sensor. By the way, none of that made any difference until I put a new/old CPU in it. Save yourself some time and just buy another computer. Anyway, I’m glad I did it. But when I put the tank back on, it went down to the gas station filled it up it almost showed all the bars, but it drops very rapid right now. It shows three bars on the Center stand and I’ve only run 54 miles. I get around 45 to 46 miles per gallon with the bike so I’m only about a gallon low. Is there any fix for this or should I just change out the gauge in the tank, or should I say sensor? Also, I have run three tanks of fuel through it since I put it back together. It still does that. I’m just go by mileage when I need to fill up, but it would be nice if the fuel gauge correspondent to how many miles I went. Do I need to change the sensor in the tank? Or?
Thanks
Dale
 
Yeah, both of mine, a 2012 & 2004, have the same problem. The 2004 does better, but I've pulled it out and cleaned it up, so it stays higher then the 2012, which I've never touched. And since I go more by how many miles I've traveled, I really don't pay that much attention to them.

So, my guess would be, at some point when your gas is down to the lower tank, prop up the upper tank and then remove the float assembly and see if you can clean the float contact area. If that doesn't fix, a new one would be your next move.

Which looks to be around $104+

2026-FuelSendingUnit.jpg
 
You may have gotten some oxidation on the resistor strip. I would remove the sending unit and carefully clean the resistor with a pencil eraser and then check the resistance while you move the arm up and down. You want to see an even rise in the resistance as you move the arm.
 
Thank you guys for your response. Next time I’m down to a gallon of gas. It’ll pop that tank back off and clean that sender. I guess it was good ol California gas evaporated and left a film on it. We’ll get it fixed. I’ve got 54 miles showing on the odometer on a full tank and it shows three bars. As long as I keep remembering to reset the mileage when I fill up, I’ll be good for a while. Thanks again guys.
Dale
 
I had a different but similar problem about 8 or so years back with my fuel gauge. I poured in double the recommended amount of SeaFoam fuel system cleaner and let it soak for a while. I did this for three or four tanks always keeping the mixture at double the recommended and letting it soak at that concentration for as long as I could.

I figured a couple of cans of SeaFoam was cheap enough that it was worth giving it a shot and this fixed my problem and it has never recurred since.
 
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