I own a 2010 St1300, the fuel level gauge shows like from Full until Half with some questionable accuracy, after that gets stuck at Half , does not get lower than that. Any advice, looks like the lower tank has a sensor which is not working. How can I fix it?
Wrong Fuel Level Gauge Indication on the Dash Board
- Thread starter julian_camino
- Start date
It looks to me like the lower tank simply houses the fuel pump and the fuel level sensor is in the top tank. Shouldn't be too hard to get to and manually move the arm to see what the gauge indicates. The sensor isn't cheap, about $100.
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The fuel gauge's last two bars including the blinking "reserve" single bar on the gauge are indicated by a sensor - a thermistor - attached to the fuel pump assembly in the lower tank. If the first 6 bars of the gauge don't display correctly that indicates the problem is probably the upper tank's float assembly.
Andrew Shadow
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The low fuel warning in the lower tank is only activated when the fuel level gets below two bars. If the reading is faulty at 1/2 tank, the problem is with the fuel gauge sending unit in the upper tank. Most likely fault is with the sending unit in the upper tank. You can see and move the float arm through the tank filler hole to do the below test without removing it from the tank but, be careful not to bend the arm or force it any more than necessary to move the sending unit in to the position needed to conduct the test.
Andrew, thanks for the reference measurements. The gauge does not go below Half, works only from Full to Half, I have no way to see the level in the lower tank. I would guess that the Fuel Level Sensor which is being installed in the upper tank is responsable of that working area, from Full to Half, below Half it might be the task of the lower tank sensor, if there is any. I can get around using old style of counting miles from Full Tank, reminds me of the good old days of riding!The low fuel warning in the lower tank is only activated when the fuel level gets below two bars. If the reading is faulty at 1/2 tank, the problem is with the fuel gauge sending unit in the upper tank. Most likely fault is with the sending unit in the upper tank. You can see and move the float arm through the tank filler hole to do the below test without removing it from the tank but, be careful not to bend the arm or force it any more than necessary to move the sending unit in to the position needed to conduct the test.
As many have said, your problem doesn't seem to be related to the lower tank, so forget about that for now. I recommend riding it until you only have fuel left in the lower tank (e.g. one gallon left total). Then you can freely check the level sensor in the upper tank as described above (resistance). The first 200+ miles after filling your tank is all about the upper tank...
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Post #4.
Andrew Shadow
Site Supporter
No, you have misunderstood.
There are eight bars on the ST1300 fuel gauge. The first six bars starting from full are controlled by the fuel sending unit in the upper tank. The sensor in the lower tank has an effect only when the fuel level gets down to two bars on the gauge. You wrote that your faulty indication happens at 1/2 tank. At this fuel level, the sensor in the lower tank has nothing to do with it.
If your problem exists when there is still plenty of fuel in the upper tank, the gauge reading at that fuel level is controlled exclusively by the fuel sending unit in the upper tank. This means that your problem is the fuel sending unit in the upper tank, the fuel gauge itself, or the wiring between the two. The easiest test to perform to start diagnosing this is what I gave you in post # 5 above.
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Just being a touch picky here but that is not quite right. The first seven bars are driven off the potentiometer on the upper tank float. The last bar is purely indicated by the thermistor in the lower tank. If the upper gauge is not reading quite right, you could either drop from more than 2 bars to 1 suddenly, or be sitting on 2 bars for quite a while before hitting 1.
Yes.....
Read post #11 of this thread.
Fuel Gauge | ST1300 Related
Merry Christmas to all. I have a fuel gauge that will read between 3 and 4 bars when the tank is full, and not go below 2 bars when I only have little more than a gallon left. Last fill, when down to about a gallon left, the bar was flashing after I filled the tank , and then resumed 2-3 bars...
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This sounds like the milk pitcher in 1001 Arabian Nights that refilled itself after pouring out milk. And you are complaining at today's fuel prices?
Andrew Shadow
Site Supporter
I am in Montreal, a harsh winter city. I haven't ridden my ST since last fall. When I was writing it, I couldn't remember whether it was one or two bars that flashed. I knew that it made no difference to the OP's issue, or what diagnostic procedure he needed to start with, so I barreled ahead.
That's the story that I'm sticking to!
I had the familiar ( to some of us) problem of the gauge going to 4 bars, getting stuck there, and then all of sudden go to the flashing bar. After reading how the fuel gauge worked, I decided to try cleaning it. I got a new gasket for the sender, and took the tank off.
Sure enough, on removing it, and testing it, a few of the segments were not working too well on the sending unit. Using an abrasive eraser on it, I cleaned it really well, and Voila'! It started working just fine. It can be tested out of the tank with am ohmmeter. Has been good ever since. I replaced the big fuel tank hose at the same time.
Sure enough, on removing it, and testing it, a few of the segments were not working too well on the sending unit. Using an abrasive eraser on it, I cleaned it really well, and Voila'! It started working just fine. It can be tested out of the tank with am ohmmeter. Has been good ever since. I replaced the big fuel tank hose at the same time.