Repairing that awful fuel sender unit

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thebigbread
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Location: Citronelle, Al (north of mobile)

Repairing that awful fuel sender unit

Post by thebigbread » Sun Nov 26, 2006 8:46 pm

so, tired of that "broken" fuel gauge? there could be 3 things wrong:
1. broken gauge
2. improper wiring or ground
3. broken or corroded sender unit

IF your answer is 3, here is how to fix it:

1. flip up the rear bench seat
2. pull back the carpet to reveal a small metal sheet screwed on with 3 screws
3. disconnect the wire coming from the panel & remove the rubber seal on the metal.
4. unscrew the panel to reveal the sending unit, secured by 6 phillips screws.
5. after unscrewing, GENTLY pull up & moving the unit around, to get the float out.
6. replace the metal cover panel to prevent your car from smelling of gas fumes & preventing a headache.
7. remove the small square panel near the top of the unit by simply prying 3 tabs out of the way.
8. use sandpaper & LOTS of carb cleaner to remove varnish & rust.
9. test by using a multimeter & the ohm setting, with the left & right contacts on the connector. reading should be 110-145 empty & 2-9 full.
10. IF reading is inconsisstent, repeat 8-9.
11. when reading is consistent, reinstall sender unit
12. also, if your idiot (low fuel) light is not working, sand & carb clean the rod & copper point with the copper point at the end.

thats all, folks
1984 2wd wagon, "bottle rocket": http://www.myspace.com/1984tercel
1995 Isuzu TFR-S, "Shorty": no cardomain page yet

Iain
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Location: London Ontario Canada

Post by Iain » Sun Nov 26, 2006 9:39 pm

Thank you sir, I'll be doing that this week.

Just the info I was looking for, thank you very much!

-1992 TCR10 Previa LE -Thanks Jetswim-
-1987 AL25 Tercel SR5 -Sold To Jetswim-
-2000 PL2000 Neon LE -Sold to spencersummerfield-
-1999 PL Neon SE -Stolen, recovered cut in half. R.I.P.-
-1987 AE86 Corolla GT-S Coupe - Sold (I want it back!)-

coltarms
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Post by coltarms » Mon Nov 27, 2006 7:03 pm

If this works on the Badd Turkle I'll kiss you!

takza
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Post by takza » Mon Nov 27, 2006 8:08 pm

I'm not so sure about the sandpaper...I've heard it is easy to damage these things. Some say to use solvent only?

Maybe solvent and a dish scrubber or steel wool?
Give a boy a gun-give a biatch a cell phone-and pretty soon you almost got yourself a police state.

Orwell said: War is peace! Freedom is slavery. Ignorance is strength...

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thebigbread
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Location: Citronelle, Al (north of mobile)

Post by thebigbread » Tue Nov 28, 2006 12:21 pm

takza wrote:I'm not so sure about the sandpaper...I've heard it is easy to damage these things. Some say to use solvent only?

Maybe solvent and a dish scrubber or steel wool?
i used 400 grit, maybe others used coarse 120 or something like that. p.s. this guide was for al21s, not sure if al25s used the same area for the sender.
1984 2wd wagon, "bottle rocket": http://www.myspace.com/1984tercel
1995 Isuzu TFR-S, "Shorty": no cardomain page yet

Iain
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Location: London Ontario Canada

Post by Iain » Tue Nov 28, 2006 7:59 pm

...other than the sender being under the carpet in the trunk area on the al25....its the same...its a great help either way...thanks again :wink:

-1992 TCR10 Previa LE -Thanks Jetswim-
-1987 AL25 Tercel SR5 -Sold To Jetswim-
-2000 PL2000 Neon LE -Sold to spencersummerfield-
-1999 PL Neon SE -Stolen, recovered cut in half. R.I.P.-
-1987 AE86 Corolla GT-S Coupe - Sold (I want it back!)-

waynehoc
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Post by waynehoc » Wed Nov 29, 2006 7:47 pm

This post inspired me to pull the sender from my gas tank last night and have a go at fixing it.

What my gauge has been doing for years is go to dead empty when filled up at the pumps, and when I had done about 350km the gauge would start to move up off empty, eventually peaking at just under 3/8 full, then slowly drifting down to empty again. The idiot light has always worked, coming on when the gauge was at the close to empty mark, on the way down again. If I filled up at this point, the tank would take about 40 litres of gas to top up.

So now that I have fixed it, with 300km on a full tank, the tank now shows just under 1/2 full. Don't think I've ever seen it show that high, at least not in recent years.

I 'cleaned' the copper windings in my sender with a fibreglass burnishing brush even though the windings looked okay, even under a 10x magnifier, but what I found was the main problem was that the moving arm which contacts the windings, actually only was making contact at the area corresponding to a tank about empty to 3/8 full.

What I ended up doing was bending the arm in such a way that good contact was made over the full range of the windings. This did the trick, and empty ended up reading about 120 Ohms on my VOM, with full reading about 2 Ohms.

Took a few pics

Image


Image


Image

Cover removed after bending up the 3 tabs


Image


Image


Image

Shows one of the float travel stops bent back enough so I could get the moving arm out in the open to bend it to make good contact with the windings for the full travel of the arm across the copper wire windings. Pic shows the back side of the moving arm, which was worn in an irregular manner, preventing good contact over its full travel over the copper windings.

Image

PDXSR5
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Location: Portland Oregon

Post by PDXSR5 » Thu Nov 30, 2006 1:51 pm

Yeah on my first rig years ago my gas guage did that only read when it's near empty thing and it drove me crazy. My new rig seems to be doing ok but I have just figured out another part I'm gonna scrounge off my parts car before I trash it.
No, it's not a Subaru!

Mac
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Post by Mac » Sat Dec 02, 2006 9:51 pm

I tried it today, but I think my sender is beyond repair, hevily rusted/corroded, it sat for a number of years with half a tank of gas. the sender in the above picture looks 100 times better than mine.
Tercel 4WD "POWER WAGOON" with 4A-C
aka: "no powa steering tercel, oh oh oh!"
mods: ignition at 10 DBTDC and 90 octane gas.

Jts
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Post by Jts » Wed Dec 06, 2006 1:03 am

thanks to the OP, i decided to do mine today. Fuel level has always shown slightly above empty ( i just got the car and it has a full tank)

On the 4wd wagon, the sensor is right next to the spare tire, to the right. No need to mess with the seats or anything. Just open the hatch and pull up the carpet

I pulled out the sender and cleaned it. It looks like the wiper had worn itself down and wasnt making very good contact. I bent it as best I could and now it reads 1/2 tank, thought its possible i've burned a 1/2 tank while working on it. All in all, a very easy thing to try and fix.

As a side note, to those wanting to test their gauge cluster. If you jumper the two outside wires of the harness (pins 1 and 3), this causes the the gauge to try to read full tank. If your gauge does not move, it means the wiring or the gauge is bad. If it maxes out, the gauge is fine and the sender is the problem. Pins 2 and 3 (or 1 and 2, depending how you look at it)
will trigger the gas light. Try this for a second to see if the bulb and wiring works if you dont think the gas light works.

Thanks to the OP for attempting this first

takza
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Post by takza » Wed Dec 06, 2006 5:02 am

Having just gotten into an intank EFI fuel pump...there are some cautions people should be using when doing this kind of job:

* try to do it with no more than a few gallons in the tank

* remove the negative battery cable FIRST

* try to do this job out in the open and away from buildings, etc

* do not make sparks around the tank...such as using power tools...hammers/chisels...etc

* be sure all electrical connxs are sound and there will be no shorts and so forth when it's put back together

* have a fire extinguisher placed back away from the job...so you at least have a chance

Not trying to ruin all the FUN or anything...but if you burn yourself and your car up....how you gonna keep posting stuff? :?
Give a boy a gun-give a biatch a cell phone-and pretty soon you almost got yourself a police state.

Orwell said: War is peace! Freedom is slavery. Ignorance is strength...

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mightyterc
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Post by mightyterc » Tue May 22, 2007 4:11 am

a great post!!!
gemini recovery vehicle

tercle
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My tercel:: 1985 SR5
Location: Seattle

Re: Repairing that awful fuel sender unit

Post by tercle » Wed Nov 14, 2012 9:41 pm

For delicate electrical contacts, I like a fresh pink pencil eraser and windex.
That's what I used on the windings on an old sender I fixed once.

Highlander
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Re: Repairing that awful fuel sender unit

Post by Highlander » Thu Dec 13, 2012 1:45 pm

I never had a problem with sender units until I had an '85. the wife's was really bad and would never read anywhere near full. When I took the sender apart, I found that the wiper had actually worn away, letting the edge make contact at a level near 1/2 a tank. I cut, bent and wrapped a small piece of copper sheet over the wiper and soldered it in place. The sender now works like it should have all along.
One note if anyone tries this- be sure to lift and hold the wiper off of the coil before soldering to keep from melting the insulation between the coils. :shock:
'83 SR5-299K, -tRusty!
'85 SR5-265K--GOLD
'85 SR5-285K-- GOLD-New engine!
'85 SR5-238K -- Teal-Killed by a DD
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dlb
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Re: Repairing that awful fuel sender unit

Post by dlb » Thu Dec 13, 2012 9:07 pm

i had a non-working fuel sender. having no idea what was normal, i figured the arm that moves should always be in light contact with the plate behind it. the arm wasn't touching at all so i bent it so that it did throughout its range of motion. seems to work fine now.

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