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I am going to convert my M38 from 24 volt to 12 volt. Does anyone know if the sending unit from the civilian CJ 3 will work in my fuel tank? Obviously, I would need to change the gauge as well. Thanks!

In theory, yes. The CJ3 sender won't have the douglas connector on it, though.

Also, be aware that the M38 fuel tank is about 1-1/2" taller than a CJ3 tank, so you'll have slightly more fuel in the tank than your gauge will show (no bad thing).

Wbr,
Owen.

If you are interested in selling the 24V items, please PM me. Thanks

It is best to buy a brand new aftermarket 12 volt fuel gauge/sender set. They have adjustable senders and they can be set up to give very accurate indications. And of course they are a matched set electrically.

The sender screw holes in the M38 tank are laid out different then CJ3A tank.
You will have to accommodate this difference no matter which sender you use. This is best done by re-drilling the sender to match the existing M38 tank screw pattern.

Any suggestions as to who/where might be best to purchase aftermarket 12 volt fuel gauge/sender set? Thanks again.

Start with the two most popular brands, VDO and Autometer

I though I would reply to this old post as I have some relevant information to offer.

I have both an M38 as well as a CJ3 tank. Not sure if it is an A or B.
Both came with the senders.

Just for grins I thought I'd see if the CJ sender would fit on the M38 tank.

As Wes noted above it did not at first. I then began to rotate the sender to see if the holes would line up some place else and they did.

Apparently the sender holes are not symmetrically placed around the opening and the flange on the CJ or the M38 units and tanks.

The CJ sender I have has SW, USA, and PAT PND stamped into the top.

So for those guys wanting to use the M38 tank with a 12 volt system the CJ sender will fit. Just rotate it around until the holes line up.

As Wes mentioned, you will not get an accurate reading at the low level and will show empty long before you are, but that may not be a bad thing.

Also watch out for the direction of swing on your float. And remember to match whatever float you use to the matching gauge. A later cj float from the single large rounf instrument cluster will make this difficult to do.