Fuel Sending Unit Install Question

Fuel Sending Unit Install Question


1983 CJ7
Engine is from a 1979 CJ7 and is 4.2L 6-cylinder.
I recently bought an 83 CJ7 to work on as a project. I dropped the tank when i was trying to find a leak in a fuel line. The gas gauge (and temp, and speedometer) doesn't work, so I thought while I have everything apart, I would replace the Fuel Sending unit, and then later the speedometer assembly. Well...an interesting thing happened...

When I dropped the tank, I was getting ready to figure out how to remove the fuel sending unit. I barely even touched it and the whole unit just came right out, no problems at all. I didn't unscrew, unbolt, unglue, anything. Surely the fuel sending unit doesn't just "sit there??" I ordered a replacement unit, but I'm confused as to how it's supposed to all go together. I would think with it just sitting in the tank, gas would leak everywhere if you overfilled the tank.

Anyone help a new guy out? I'll be glad to post a pic if that will help...
It appears to be an aftermarket tank and sender. This is a good time to check the operation of the sending unit. A repair manual should have correct instructions on how to check that with an ohm meter. There should be a retainer of some sort that holds down the sender and seals it to the gas tank. It might have the maker of the gas tank marked on the tank somewhere and you could contact them.
The big nut looking thing should unscrew. I use large channel locks. The sender unit goes in the tank and the big nut holds everything together. Should also be an O-ring to seal it.
I found a link to a great website where someone had gone through the same install process. Clearly my jeeps PO did not get the same information as the unit was not installed correctly. My new sending unit appears to be defective right out of the box. The arm with the float on it clicks and hangs. You have to sort of force it to continue on through its range of motion. The old one still works smooth as can be, and tests out perfectly on the ohm meter so I'll be reinstalling it...the correct way. Guess I'll be sending the new one back...

Here's the link for anyone else with a similar setup who might have some questions.

Ken's 1985 CJ7 refurbishment thread - Page 26 - JeepForum.com
When your tank is empty check the resistance of the sending unit. It should be 73 ohms.
It simulate a full tank remove the sending unit and move the float to the up position. It should now have about 10 ohms.
Minor adjustments can be made by bending the float arm. There is a tab that prevents the float arm from going too low. If the arm isn't shaped right it may hit that tab before it touches the bottom of the tank.
My sender still doesn't work properly. When tank is full, gauge reads 3/4. When the tank is empty, the gauge reads way below empty. I tried bending the tangs to fix this but it only worked for a while. Maybe my in tank fuel pump is messing things up. Also, my new plastic float immediately sank.

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