Help Identify Fuel Tank Sending Unit

[mopar70]

I pulled this out of the gas tank and need a new fuel tank sending unit for my 1970 challenger. This car was a small block car and now has a 383. Previous owner put in a new tank but used the old sending unit.

 

[mopar70]

Pics

Here are the pictures

 

[mopar70]

What size is this one? And what size should I get?

 

[DetMatt1]

If you don't need to replace it, don't! The ones they're making now are of very poor quality. I think that's the same unit Ma Mopar used for the U code cars. I have actually spent a half a day repairing the one out of my Imperial for lack of wanting to buy the new garbage!

 

[mopar70]

My fuel guage needle moves a little when i plug this in and dosent show proper readings. Do you know how to fix it?

 

[moparleo]

The most important reading is Empty. I would go ahead and power up the sending unit and adjust the float to give a correct empty reading. Make sure that the float does not leak first. All the sender is, is a variable rheostat. The unit must be grounded properly to get a correct reading.

 

[mopar70]

The sending unit is a mess not worth fixing up I want to order a new one what size should I get?

 

[moparleo]

The 3/8" will flow more fuel as long as the rest of the fuel lines have been replaced with the same 3/8" diameter . Other wise it came with a 5/16" unit.

 

[DetMatt1]

The sending unit is a mess not worth fixing up I want to order a new one what size should I get?

You'll likely regret replacing with new, my 2 cents.
Like Leo said, the unit must be grounded properly to work accurately. Was the ground strap in tact when you removed it? I replaced the unit in my fathers Challenger a couple years ago because the float got a pin hole in it. Gauge never worked properly with new unit so I then ordered just the float and installed it on his original unit and it worked fine again. A good friend put 3 replacements in his Road Runner before giving up on them and fixing his original and he's a service manager at a Chrysler dealership and has had a list of classic Mopars as long as my arm. All I'm saying is just make damn sure you absolutely have to replace the old one before buying the new junk. That 5/16 supply will feed a very healthy big block without any trouble.

 

[sheetmetaldan]

All it may need is a thin copper wire soldered to the swing arm to the body of the sending unit. They are notorious for poor grounding. I used to have some good info on fixing these i`ll see if I can find it. My sending unit was dead and I brought it back works great now no problems.

 

[mopar70]

Floats got a hole and the wire broke off because its rusted. Also the cover for where the fuel goes through was brittle and really dirty.

 

[sheetmetaldan]

Floats got a hole and the wire broke off because its rusted. Also the cover for where the fuel goes through was brittle and really dirty.

I did not see a wire on your float arm are you talking about that strip of metal?

I sanded off the rust/crud on mine at red arrow in pic (btw not my sending unit just a pic I found) and re-soldered this improved continuity down to the part of unit that houses swing arm. If you can`t save that strip of metal the pic of the sending unit with the yellow wires will do the same as that strip of metal. The wire from the swing arm to the body of sending unit keeps continuity better than at the swing arm pivot point.

Ford sells an exact replacement float ball too! Around $10-$15 bucks I think.

 

[sheetmetaldan]

Another pic of the wire to the swing arm. Just use a thin wire and make sure it doesn`t interfere with the travel of swing arm. It`s really an easy fix!

 

[DetMatt1]

Good posts Dan! What isn't shown in pics and wouldn't be easy to see anyway is the minute wire that makes up the windings for the reostat, at the beginning is attached to the ribbon wire through the housing. Be very careful to make sure it stays in tact.
Mopar70, it does sound like yours could be a good candidate for replacement if it is THAT bad but you've got nothing to lose by trying to fix the original.