Repairing that awful fuel sender unit

[tercle]

The wiper contact had worn off the 47 year-old Mopar sender I fixed.
The wiper arm just had a small hole where the contact used to be.
I got a packet of small brass fillister screws from a hobby store.
2-56, I think. And some brass nuts. I damaged the brass threads on the screws a little with some diagonal pliers to bind the nut as if it was a locknut.
I filled the standard slot with electrical solder (a brass brazing rod would've been better) and then filed it flush to the fillister shape.
You can grip the sides of the tall fillister head with pliers while tightening the nut.
It makes a nice button with a dome face, similar to the original button contact.
If there's enough clearance for the nut.
I bent one of the limiter walls down so I could work on the wiper arm away from the windings.
I'm not sure if the same technique used will work on a 1980s Toyota sender.

[GotToyota?]

I did this today and I don't think it corrected my gauge issues, sadly.

When I fill it up the gauge runs about 2/3 to 3/4 full. When I filled it up after I first bought it, the gauge read around 1/8 and only took 5 gallons to fill up.

I'm gonna drive it around soon to see if it worked. Sanded the copper real good and used carb cleaner as well to get all varnish off.

[GotToyota?]

Just an update, filled up my tank today and it's reading full now. Turns out my efforts worked!

[Mad_Marx]

Thanks for this! My fuel level wasn't reading all the way to "F" when the tank was full. I also noticed the low fuel light would come on around the 200 mile mark instead of 250-ish like my last car. If i fill it when the low fuel light comes on, I can usually only get 8 or so gallons in. According to the specs I found the tank is rated at 13.2 gallons, that means 5 or so gallons still in the tank and I'm getting a low fuel warning. That seems premature.


When I took apart the sender I noticed this build up on the resister coils, I was able to clean it off with a small brass bristle brush. The gauge seems to be reading more accurately now, but I won't know for sure until the low fuel light comes on and/or I fill up again.

So, I was wondering if anyone knows what this build up came from? and/or is there a way to prevent it in the future? My guess would be preservatives or additives in the fuel. It's very hard to find non-ethanol fuel here in Boise, and even harder to get High Octane non-ethanol.


Thanks again for Repair Forums stuff

M_M

[dlb]

i did this once on a project tercel several years back, and again this week on my ae95. both times were successful.

what i noticed this time is that the gauge in the corolla had always been a little off but not too bad. however, after sitting for several months while i was driving tercel #7, the gauge was reading quite a bit more inaccurately than ever before. like others, i found some varnish buildup on the contacts so i used 400 grit sandpaper and gently removed the varnish. the gauge reads perfectly now.

to answer mad marx's question above, i'm not sure what specifically causes the varnish but it is a common thing with all gas engines, like lawnmowers and chain saws as well as cars. i suppose it is why carb cleaner, injector cleaner, seafoam fuel treatment, etc are around. i'm sure if we dug deeper we would find similar varnish buildup in other areas of our fuel systems but perhaps the sensitive fuel level sender is the only area that bears obvious effects. in light of this, i will probably do a seafoam fuel treatment in the near future. i doubt i'll notice any improvements from it but i've found it very effective as an oil additive and lots of small engine repair places swear by it too, so i'll give it a shot and consider making it a once or twice a year maintenance thing.

[irowiki]

I've tried repairing 3+ fuel senders with no luck.

They also tend to have a lot of corrosion in the plug which probably doesn't help!

[dlb]

yes, i noticed a lot of bright blue corrosion on one of the contacts in the plug. i sprayed electrical cleaner in there and plugged/unplugged it several times.

[lannvouivre]

We took the sender apart and bent the wiper arm so it was contacting the windings, then tested with an analogue multimeter to verify it was contacting the whole way. I feel like a more robust arm and spring would be great mods, if someone was smart enough to engineer something.

[Petros]

not a bad idea, the factory ones "only" last 25 to 30 years operating in a corrosive environment. You need more durability than that?

Of course now that crappy federal ethanol blend makes it even worse. There might be some generic after market solid state sender that can be adapted.

[irowiki]

The problem Peter is finding new fuel sender units

[4wdEconoBox]

Well I fixed the sending unit and it cleanly sweeps from 6.5 to 113 ohms. But the the gauge still reads erratically, I found if I tap on the gauge cluster the gauge will start reading correctly for a little bit, is there any fix for this, maybe taking the cluster off and checking/cleaning the connection on the back of the cluster?

[xirdneh]

i have tweaked a few of them
some worked afterwards and some did not
the contact arm seemed to always be the problem
its hard to bend it for a bit more tension cause the end is resting on the coils
ended up bending it "slightly" by using two needle nose pliers near the base
the trick is to twist them in opposite directions
got two to work with that
i also sand the coil very lightly with 400 wet/dry sandpaper
then triple up the sandpaper and slip it between the arm and coil
then move arm back and forth over it to clean up underside of arm

[irowiki]

I have not had any luck trying to clean and fix 4 senders now. Still have a broken gauge.

[4wdEconoBox]

I do believe that I fixed it. I took the whole gauge cluster apart so that I could get the fuel gauge out and then I reflowed all of the solder joints. I'll post a couple pictures, they looked crusty and I'm guessing the solder joints had cracks in them. After 30 years it was bound to happen I guess. I had to do something similar to that Volvo I had, except it was for the speedometer.

[4wdEconoBox]

Little update, I definitely fixed it and its already coming in handy! I'll do a complete write-up with pictures if yall want me to show how to take the cluster apart and how to solder and fix the gauge itself!