This weekend I pulled the fuel sender to recondition it (again). I had it out about a year and a half ago and cleaned the steel portion of rust and replaced it.

Recently the sender got stuck again, so I pulled it and dismantled it. Here's what I found:

The rod was rusted badly. There is no question that this is in large part rust, the metal is badly pitted. It looks like this piece was originally chromed. I was hoping to be able to remove the center piece and use a lathe to make a replacement, but the top of the sender seems to be press fit or glued together. Instead of spending 250$ for a new sender, and since my local junkyards are all out of w123's, I decided to try to refurbish this.

(There are some posts on how to dismantle the sender to clean it available online already, I'm not going to repeat these instructions. Google is your friend)

First step is to remove the wires. There are two wires that run the length of the sender. One is a standard copper wire that acts as part of a switch to turn on the reserve light. I marked both contacts where that wire goes with a sharpie to make sure I knew where it went. The other wire is much much thinner and appears to be a nichrome resistance wire. It loops from the contacts at the top of the sender, down through the float to the base, and back up to the other contact. You need to de-solder all these wires and place them aside somewhere safe. A tip to remove the heavily oxidized old solder is to wire brush it thoroughly (I use a brass wheel on my Dremel), then heat it up and add a bit of fresh solder. The new solder acts as a thermal bridge, and typically helps you re-melt the old solder. The copper wire probably has tiny hooks bent into it at the ends, so you may need to push it in the opposite direction you would expect to once the solder is hot to remove it.

Now you can remove the base. This is held on with a nut and washer. You may want to wire brush the threads before you try to remove it, depending on how badly rusted they are. The bottom piece should slip off.

Next there is a square "nut" - more of a spacer. This seems to be press-fit, and probably held up with some rust. Mine kind of fell off after some sanding.

Finally, you can remove the float. Let it drop to the bottom of the sender, then twist it a bit and it should come off.

Now it's time to clean up the central rod. Sandpaper works well, though for some reason I didn't think to use my bench grinder's wire wheel - which would have been quicker and easier.

Now the metal is relatively rust-free, and the float should work smoothly - but if you re-assemble it, chances are it will rust again in short order (sanding the rust off probably removed more chrome, making it more likely to rust again). Optimally, we'd have this re-chromed, or a new piece made and chromed, but since I can't figure out how to dismantle the top of the sender, that's not really an option. Instead I decided to use POR-15 to coat it. I am hoping that this will hold up in diesel fuel, but really only time will tell. There are certainly other products that might work, this is just what I had on-hand. Follow the instructions for your coating, and try to apply 1 or 2 thin even coats. If you coat the threads at the base, make sure you clean them up before the coating cures. I don't have a dye that's the right size, so before the coating cured, I ran the nut up and down the threads a few times to clean them out. Be sure to remove the nut and clean everything before it cures completely though. There is also a large washer/cap at the base of the sender that may be rusty, I coated that as well.

Tonight I will probably try to get some additional pictures and re-assemble the sender. I'm planning on letting it cure for a couple days before I put it back in the tank (it's too hot to drive my car right now without AC right now anyway).

Total cost to rebuild the sender so far was on the order of a few dollars for coatings and an hour or two of work. A new one is a couple order of magnitudes more expensive, so I'm happy to try to work with what I have.

I'll be draining and coating my tank shortly. I plan on pressure washing it with some heavy degreaser, shaking some chain or nuts and bolts in it, then using the POR15 kit with it's degreaser, prep, and coating. I've heard pretty good results with this, but if it doesn't work, I can always get another tank later.

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