Refurbishing the Fuel Sender

[Akula69]

Like most of us, over the years I have snapped up the fuel senders out of trucks that I find in the JY. The "collection" was basically dormant until my son's truck started leaking fuel from the sender, and I pulled out what I had to take an inventory.

 

Both the senders I had in storage were corroded and had some pitting, but the worst problem was the lead from the harness to the float potentiometer on both were broken off. Although the 'before' pictures have been lost, I removed the old pumps and wiring, carefully taped up the potentiometers and sand blasted the units. This is the result:

 

 

Note in the picture above we installed a bullet connector on the negative lead so any future repairs would be easier to complete. At this writing two sets of the origonal harness were still available (PM me if you want the link) for $75.00 each, but mine were still functionable with a good cleaning.

 

The 'broken' lead:

 

 

Before I even attempted to repair the broken lead I consulted with Don in the forum to get a better understanding of the potentiometer. I also called this place http://tristarrradiator.com/ and got a quote for repair. The quote was $125.00 per sender, plus the price of replacement parts. (Interestingly enough, the site will also sell just the potentiometer that is a similar range as the ones we use). After pulling out the multimeter and ohming out the ones I had, it was discovered they were both still good (range from 5 ohms to 95 ohms), so I decided to repair them. I clipped the broken end and put a new connector on:

 

and then went on the hunt for #000 machine screws and nuts. Although I found a site that did sell them (http://www.clock-keys.com/pdf/Categories/fasteners,%20pins%20&%20grommets.pdf bottom of page) I also found that the mandrel from a dremel cut-off tool also had the same size screw, and could be cut to fit. (cheaper too!)

 

 

 

 

After carefully removing the remains of the brass rivet (carefully, as one end of the potentiometer wire wraps around it!) the small machine screw is inserted from the inside of the potentiometer and the wire terminal, lock washer and nut is tightened on the outside. After checking again with the multimeter to ensure it still worked properly, we went on to the next step.

[Akula69]

Now the question I posted here in the forum about fuel-resistant paint became a pressing matter. I spoke at length to the POR-15 folks, the result of which was they could not specifically state their product would be fuel proof. I moved on to a product commonly used by scale RC modelers called Klass Kote, which is not only fuel but also nitro-methane proof. Site link: http://www.klasskote.com/. According to the manufacturer, this product will not dissolve in gasoline if allowed to harden for 7 days or longer. Although the company makes several colors, I chose the 'battleship grey' color and the white hardener, simply because I thought it would look better. The two must be combined in a glass or steel container (will eat plastic containers!) and I (at first) tried to draw the correct amounts out the cans with plastic syringes (mistake!) and ended up using a glass measuring cup. It has to sit for 45 minutes before application, and then hardens quickly after that, so we learned to only mix a small amount at one time...

 

 

 

I used a regular brush to apply the finish, and got good results:

 

 

 

THe thickness of the epoxy also filled some of the minor pitting as an added bonus. Now we wait for paint to dry....

[Akula69]

The re-assembly of the senders brought a new problem into light - the 'o' ring under where the harness enters the top of the sender is unique. it is standard in size (ID and OD) but it's diameter (thickness) meant it was not standard. I finally found it at the local NAPA store - it unfortunately does not have a part number so you would need to take the old one in for comparison.

 

 

Then, fastening the push nut so leaks do not occur:

 

 

 

and finally, re-attaching the other wiring and taping the openings (keeps bugs out) for storage:

 

 

 

We bought new locking rings and 'o' rings for the senders - they are still commonly available but we got ours at NAPA: http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?A=STPLO01_0261766611&An=599001+101989+50038+2038006&Ar=AND(P_RecType%3aA).

 

and, finished:

 

 

All-in-all, we spent about $60.00 for refurbishing the two senders.

 

My son's sender had developed a leak at the junction of the tube and the top (outside) plate of the unit - we ended up using JB Weld to repair his with good results. If either of the units here would have had non-working potentiometers I would have send them to the rebuilder, as adjusting the potentiometer is beyond the skills I have.

[HOrnbrod]

Great job and writeup Jake. :beerhead: Now you can sit back and wait for the PMs to start pouring in from people needing to get their broken fuel sending units fixed. :yes:

[bigalpha]

Before I even attempted to repair the broken lead I consulted with Don in the forum to get a better understanding of the potentiometer. I also called this place http://tristarrradiator.com/ and got a quote for repair. The quote was $125.00 per sender, plus the price of replacement parts. (Interestingly enough, the site will also sell just the potentiometer that is a similar range as the ones we use). After pulling out the multimeter and ohming out the ones I had, it was discovered they were both still good (range from 5 ohms to 95 ohms), so I decided to repair them. I clipped the broken end and put a new connector on:

 

The sender in my MJ is structurally fine, but the potentiometer is borked (ohmed out wrong). Are the potentiometers replaceable?

[mj2stay]

That's what I would like to know. Are the potentiameters replaceable? I actually have a sending unit with a good potentiamenter that I would like to replace with my current unit. It is from a 23 gallon tank, fueling a 2.8 engine. I have a 23 gallon tank fueling a 2.5 engine. Will the potentiameters interchange?

[Akula69]

A good question.

 

Best I can tell you guys is that the web site in New York I referenced in the post does replace the potentiometer when they re-build the sender (and you can buy them separately as well) but I have never been able to remove the old one from the sending unit.

 

Seems the shaft for the float passes through the plastic case of the potentionmeter and then thru the metal mounting plate. At the time I could not find a way to get it off without severely bending it and/or cutting it (which would basically destroy the float arm).

 

The potentiometers that company sells appear http://tristarrradiator.com/Products%20Page/Products%20Page.html (see picture of 0-90 rheostat) to have the float arm as a straight shaft that simply plugs in - but there is a question as to whether it would read correctly on our gauge set.

 

As far as tank-to-tank interchange, one of the spare senders I have is from a small tank and the other is from the larger...but they both ohm out the same, and the float arms appear to be the same size (but I have not measured them). I am unaware of differences in the senders from different engine types.

[HOrnbrod]

Will the potentiameters interchange?

Someone must have realized too late that the Renix fuel sender pots wear out eventually. They are replaceable on the 91-92 HO senders.

 

[jerardisflossin]

How you got the plastic wire elbow that goes through the metal cover off to replace the gasket? I have a spare 91 XJ sending unit (same wire entrance) and I cannot get it to separate from the metal piece. I wanted to be sure I could get it off (without breaking it) before I yanked my sending unit out of the truck.

[jerardisflossin]

Ahh nah, I was talking about the yellow connector shown in the attached photo. I need to get it out to replace the gasket.