Fuel Sender Unit Mystery - Polaris ATV Forum
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post #1 of 8 (permalink) Old 06-30-2019, 10:45 AM Thread Starter
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Fuel Sender Unit Mystery

For the past few years my fuel gauge has read empty on my '08 Sportsman 800. I just thought the float was detached. and never got around to fixing. Well today I pulled the gas tank (need to change spark plugs.) and took off the fuel sender unit.

Sender unit looks good, float is undamaged and attached. I cleaned up the resistor pad with some scotch bright pad - but still it don't work. If I plug in the sender unit outside of the tank and manually move the float value it works. Yet when I install in the tank and fill with gas, I'm only get an empty reading.

A new sender unit is $450 so that's not an option.

I'm stuck on why this fuel float sender is not working properly

Any suggestions?
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post #2 of 8 (permalink) Old 06-30-2019, 11:13 AM
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Reach in the tank with a coat hanger hook or something similar and pull up on the arm to see if it'll start working. I think sometimes the float gets stuck on the side of the tank when completely empty or something. My 06 800 did that once while I was bouncing hard through some rough stuff with the tank really low. Fished the arm up just to see what would happen and its worked ever since. That was probably 3 or 4 years ago.
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post #3 of 8 (permalink) Old 06-30-2019, 01:22 PM Thread Starter
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If I reach in there with a wire I can move the sending unit float arm and then I get a reading. It's been that way for ever, so that's why I thought the float was detached.

But then this leads me to believe that the FLOAT itself -has STOPPED Floating. Never heard of such a thing, but going to get a new float. Found a guy on ebay who sells them for $15. Let's see if that solves the issue.
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post #4 of 8 (permalink) Old 07-01-2019, 11:37 AM
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The floats are usually closed cell polystyrene foam plastic - if the smooth outer finish of the unit is not 100% impenetrable, alcohol will enter and dissolve the walls of the cells making the closed cell construction open cell and it will absorb fuel like a sponge - it then becomes a sinker. It happens to carb floats frequently as the float is cast upon a metal arm. With the floats, the liquid enters between the float arm and the float material. Most fuel tank floats are captive on a spring hook - some Chinese fuel sending units have the float drilled and the float arm is simply a piece of wire bent 90 degrees, inserted through the drilled hole and held in place with a push on retaining ring. I replace sending units on Chinese scooters frequently for floats that don't float.

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post #5 of 8 (permalink) Old 07-01-2019, 11:50 AM
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I used to have a 2007 Polaris snowmachine that the float stopped floating,had to buy a new gas cap/guage assembly.
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post #6 of 8 (permalink) Old 07-07-2019, 09:16 AM Thread Starter
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Yes it was a bad OEM Float. What a joke. Polaris must use the cheapest parts. I mean a float should float for 1000 years, not just until warranty expires.

Ticked me off as I have spent tons of hours on this and years with this issue.

The replacement float from ebay was just fine.
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post #7 of 8 (permalink) Old 07-07-2019, 09:56 AM
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It's not the quality of the float, it's the alcohol in the fuel - but I have seen cracked brass and hollow plastic floats also

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post #8 of 8 (permalink) Old 07-07-2019, 11:00 AM
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Some of that bunch in Washington ought to be given an alcohol enema twice a day!!
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