Fuel Sender Rebuild

[MrMoparCHP]

This was done for my Barracuda but felt I could share here.


I have a new/reproduction sender in my car and it doesn't read correctly, it hits empty at half tank. I had been planning on adjusting the float to move empty to empty but I thought about looking into what could be done with the original.

I had three to work with and none worked.

The first one (cleanest) was looked at and the first thing I noticed was the phenolic board was slipping out so I removed it. I tested it with a meter and it was within the correct range.

All three units were put in vinegar over night and cleaned, I then looked to see what it would take to take them apart and find out why they didn't work.

The first one I noticed the pointer was off axis and was loose on the shaft so it was put aside (stripped of all parts).

The second unit was cleaned and examined and everything seamed fine, the insulator was still intact.

The rest of the parts were cleaned up and sorted through.

The board fits into the main frame on on end and on the contact bar on the other, it appears that the pressure of the pointer holds in in place.

The board was then installed.

I then took my meter and put it through the motions with mixed results, sometimes nothing, sometimes spotty. In checking I came to the conclusion that the board was originally riveted to the copper bar. The other bars and board were looked at and I felt I could solder them together.

 

[MrMoparCHP]

I first put solder on the back of the board and then the copper bar. while the bar was still hot I placed the board on and heated them till they pressed together. Once cooled off I did the wiggle test.

That assembly was put back in the frame and tested again, once again mixed results. I then noticed the the float arm had a little play in it causing the pointer to lift off the board. I bent the pointer so it would stay in contact with the board even with the play in the float arm.

Once again everything was tested and this time it all works as it should, next up to put it on the car.

There were multiple things that I saw that could have caused these not to work.
1. Filthy
2. The pointer not staying in contact with the board.
3. The board getting disconnected from the bar.


Alan

 

[live4theking]

Alan,
Great write up.

 

[fury fan]

Agreed, excellent work!
I had done some similar repairs 15-20 years ago, before repro senders were even available. And couldn't find NOS because there was no internet yet. Couldn't have afforded NOS anyway...

Good idea on the vinegar, back when I did mine I wiped them sideways with scotchbrite to clean them off. Vinegar would be better.

 

[traintech55]

Alan, You are the man, THANKS.

 

[Big_John]

Great write up.

My '70 had an issue with a worn contact on the wiper.

FWIW, the rheostat is a different configuration, but the basics are the same... Rheostat with wiper that needs to be clean and solidly mounted to work correctly.

 

[Trace 300 Hurst]

Outstanding write-up/how-to, and good additional commentary from BJohn.

This could be a Sticky. I've certainly bookmarked it.

 

[Ross Wooldridge]

The same issue can occure with dash light dimmers - clean/allign the wiper and coil and it usually fixes it up for another few decades, plus your dash lights get brighter at full on too!!

 

[Trace 300 Hurst]

The same issue can occur with dash light dimmers - clean/align the wiper and coil and it usually fixes it up for another few decades, plus your dash lights get brighter at full on too!!

Indeed, except that one of the prongs is prone (it's a prone prong!) to breaking off like mine was (thus no dome light when clicked all the way to ON). I bought a repop for $140 or so....gleaming new.

Also, love your comment about "fixes it up for another few decades".

 

[BillGrissom]

Great writeup. Thanks. Always best to refurbish parts when they are still sound. I bought a new stainless sender for my 64 Valiant and 65 Dart ($45 ebay), partly to get a return tube for fuel injection. In a bench test, at least one was erratic as the level moved. I popped off the cover and bent the wiper arm so it contacted stronger, which fixed it. I also tested w/ the dash gage (on bench, being refurbished). The gage has two screwdriver adjustments for offset and span. They are mechanical bendings of the pivot support so appear to be for the original factory tweaks and not for users. I tweaked those a bit and also had to add a parallel resistor on the back of the cluster to get the dial to read E and F correctly. That was for the swing of the arm, so not sure it will be perfect for the actual fuel levels.

In my 65 Newport, I installed a new CR9 tank (for B-body, $105) and a new sender. I will tweak it at the cluster later. Years ago, I burned up the cluster fuel gage in testing it, so installed an under-dash gage. Since then, I fixed the cluster gage in my 65 Dart which had a melted wire. That is a Ni-Cr wire so can't be soldered. The factory used some type of pink glue (epoxy?) to attach the Ni-Cr wire to the rear stud. I fixed it by soldering a Cu wire to the stud, wrapping it tight about the Ni-Cr wire off the needle and soldering. The solder is simply to secure the Cu wire. Don't know if that will be permanent. Someday, I'll pull my Newport's cluster and try the same. BTW, in early cars the cluster's 5 VDC Vreg is built into the fuel gage and is a rough on-off thermal switch. That is pre-1967 A-body or pre-1973 w/ tachometer, not sure about C-body. You can buy a better electronic Vreg on ebay ($30) to mount on the rear of the cluster and bypass the internal one. Those usually have a screwdriver voltage adjustment, which is another knob you can turn to get your fuel level reading correct. But, if you have a dial temp gage, it will be affected too. My main concern is getting the "E" reading correct on my fuel gage. The other marks are "merely interesting".

BTW, only a fool would use the fuel gage to calculate mpg (though many do). Much smarter to use the receipt at your fuel pump (calibrated regularly by State). Also use your GPS for distance instead of the odometer, at least until you validate the odometer readings.

 

[70bigblockdodge]

There is ohm values in FSM IIRC use to set new repop senders, which are never even close.

 

[fury fan]

Agreed on the repops being inaccurate!

 

[Wilkiethegrid]

I first put solder on the back of the board and then the copper bar. while the bar was still hot I placed the board on and heated them till they pressed together. Once cooled off I did the wiggle test.
View attachment 225880
View attachment 225881
View attachment 225882
View attachment 225883
View attachment 225884

That assembly was put back in the frame and tested again, once again mixed results. I then noticed the the float arm had a little play in it causing the pointer to lift off the board. I bent the pointer so it would stay in contact with the board even with the play in the float arm.

Once again everything was tested and this time it all works as it should, next up to put it on the car.
View attachment 225885
View attachment 225886

There were multiple things that I saw that could have caused these not to work.
1. Filthy
2. The pointer not staying in contact with the board.
3. The board getting disconnected from the bar.


Alan

It seems these original parts would be more susceptible to the ethanol (excess moisture) in fuel these days . Since they were designed for non ethanol use. I would like to bench test my reproduced sending unit before I put it in. What would be the proper ohms range I can look for? 63 Dodge 880. Also which app do you use to track mileage?

 

[rapidtrans]

My fuel gauge hasn't worked since I purchased the vehicle. Always reads 3/4 full.
Accurate or not my odometer is consistent and i can get about 200 miles per tank. Fill up at the 150/175 mark and I've been good.
Now that the sending unit seal has developed a leak it's time to pull the thing. This thread is a tremendous help when I inspect the thing before I go the repro route.

 

[lebaron413]

Great write up.

My '70 had an issue with a worn contact on the wiper.

View attachment 225928

FWIW, the rheostat is a different configuration, but the basics are the same... Rheostat with wiper that needs to be clean and solidly mounted to work correctly.

View attachment 225929

Hi fella's, With all this time on my hands, I decided to tackle and repair 2 of my fuel senders. Just read the great article, my concern is both my wiping arm pads are worn off, can I use a standard Elec. Solder to build them up or would a brass rod eg. Brazing work better? i'm worried about the amount of heat as they are very thin.

 

[Big_John]

Hi fella's, With all this time on my hands, I decided to tackle and repair 2 of my fuel senders. Just read the great article, my concern is both my wiping arm pads are worn off, can I use a standard Elec. Solder to build them up or would a brass rod eg. Brazing work better? i'm worried about the amount of heat as they are very thin.

Solder would wear off fast.

Possibly make a new contact from brass and solder it on??

 

[HWYCRZR]

Now I need to look at mine. Empty had the right value at 74-76 ohms, but not quite sure where full is. Gets a little wonky towards the top. Full should be around 10 OhMS

 

[HWYCRZR]

Mine was very clean, but as above the copper wiper has a hole worn through it
The windings look great though.

 

[HWYCRZR]

I think my wiper is ok? As was cleaning I noticed that the wear marks were on the edge of the copper wiper tang and not the center. There is actually a perfect round hole in the center it just had some gunk in it. I unplugged the sender wire in my car and ran it using the gauge. At the bottom stop it was right on E. At the top stop. It was perfectly on full. Now I want to drain my tank and try it out.
E- is 64 Ohms. Mid way is around 25 Ohms and Full was 9.7 Ohms

 

[HWYCRZR]

Filled the tube with carb cleaner and capped it, then let it soak a couple of hours to get some of the varnish off. Then found some pipe cleaners from the Craft Room and run through a couple of times.

Everyone talks about the sending unit retainer not working on re-pops. I think It is more the rubber gasket. I have two that are different thickness. I will go with the thickest.