Fuel Tank Sending Unit Broken

[DavidB]

Have any of you had defective fuel tank sending units and have you repaired them yourself?

My Honda Flush (not for export but similar in ways to the Spree) has a defective sending unit though I know the fuel tank gauge works. The float was initially stuck which by pulling off the small washer/keeper allowed me to rotate and pull it off. I scraped corrosion from the pivot point so now it rotates freely. Small wire fingers of the float arm run up/down carbon tracks of the sending unit giving the gauge a varying resistance and then fuel level. Parts of the carbon track have open circuited.

Have you found a way to fix the carbon tracks? Did you grind any carbon/coke, mix with epoxy and reapply? How did you remove the printed circuit board from the sending unit, by cutting away epoxy from the top and pulling the board out from the top?

[DavidB]

My unit is a 3-wire sending unit which broke the carbon trace. Has anyone taken a 1 kilohm potentiometer and retrofitted it to the fuel sending unit? Bl/Wh and Y/Wh would go to the ends with G to the wiper. Would any part of the potentiometer be incompatible with fuel? How would one reduce the internal friction of the pot. so that the attached arm could freely move up and down while driving the arm of the pot?

[motormike]

It occurs to me that any other sending unit of similar design might be used as a donor for the parts needed to repair your sending unit. Have you done any salvage yard or scooter-shop comparisons ?

[DavidB]

I don't know of any local places to find such a donor part. I'm thinking of engineering a new sending unit from a 1 kohm potentiometer, mounting the float to the adjuster knob, 3 wires to the pot, and mounting the pot on a steel bracket. I'll first immerse the pot in gasoline for a month and examine and test to see that it is still completely intact. If anyone else knows of side effects in advance, I would be receptive to them. If the carbon resistance is sprayed on during manufacture (they have spray bottles for carbon overseas, not in the States) then it could dissolve off and not work in this application.

[Ruckenstein]

How bout I sell you one for $15 shipped.

[DavidB]

Thanks. Let me get back to you later.

[DavidB]

Ruckenstein, yes, I would like to purchase a fuel sending unit for my 1985 Honda Flush. It is 3 wire and you've seen the photo of it. Please send me details.

I had thought of making one from a 5 ohm potentiometer, 300 degree total throw, and limiting the throw to 42 degrees, giving me the delta of 700 ohms which someone else posted, showing a 400-700 required range from low to high. I considered opening it up, affixing a copper clip to that part of the carbon trace and jumpering it to one end of the pot. Then use a physical block for the 42 degrees.

So let me know more. I'll send a PM.