C90 Fuel Sending Unit Repair
provided by Chris aka Lynchburg66

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My sending unit was intermittent showing empty on the gauge even after filling. This is the repair to the sender to help prevent you from having to purchase a new fuel pump at a retail cost of $560.00. First you are going to need a 2/56" thread die and some nylon nuts & washers to match. I got the nuts and washers from my local hobby shop. They were out of stock on the die so I had to get it at a local tool shop. Cost me less than $10 for the die, nuts & washers. I had a die holder already so I didnít need to purchase one. If you canít find the die & nuts locally you can try online @ Tower Hobbies. The part numbers are as follows.

Die: LXR765

Die Holder: LXR768

Nylon Nuts: LXK026

Washers: LXK035
 

I broke down the pump and removed the float from the sending unit.

Then I put the float in my vise and started threading the end. I kept going forwards & backwards till I threaded about 5/16".

I then reassembled the float to the sending unit. I will say be very careful with the wires to the sending unit as they a very thin, 22 gauge I think, and will break quite easily. They are covered with heat shrink on both ends so you will most likely not know it unless you pull on them kind of hard. I didnít use a spring washer behind the nut as all I could find at my local Ace were just a little too big in overall size. I just kept snugging up the nut till there was very little play and it was in no way coming close to not letting the float move freely.

Then I reassembled the entire pump and reinstalled it.

The fuel gauge now works properly again. This was a very easy repair and you could do it in less than 2 hours if you have the parts needed. I hope this helps anyone having an intermittent problem with their sending units.

Chris