My fuel gauge only registers after a fill up and then drops to the bottom of its range after 40 miles or so. I suspect a break in the resistor wire (nichrome) within the sending unit.

I would like to repair this by re-winding and it with nichrome wire. Does anyone have a failed unit or new preferably, that can be used to get some measurements from?

I would like to know the diameter of the wire inches (dial caliper) and also if possible the resistance over a 12" span of unbroken wire. You would need to unravel it to get an accurate measurment. I need these specs so I can get the correct resistance range wire before removing my tank.

If anyone can provide me with some specs. I will post a writeup with pictures. Better yet, if you want to send me a bum sender I will fix it (as best I can) and return it free of charge.


Thanks for your help,

 

Wouldn`t it be easier to either buy a new sending unit, or possible a good used one ?.

 

Subscribed. I'm curious about this too, mine does the same thing, pulled it out and looked at it, sure enough, little wire is worn right through. A new one is stupidly expensive, and I can't find any at a junkyard. (or cheap enough at a yard to merit buying) So i've been living with an iffy fuel gauge. If I do pull it again, I'll look at the wire and get a size...know where you can buy that type of wire?

 

does anyone know if the 3vze and 22re trucks and 4runners,2wd ,4wd use the same one , or are they all different, does the tank size matter?

the one on my 2wd 22re does not work , i have a used replacement i got a while ago .. just never installed it . Its been easier to just fill up every three days . i also have a 3.0 gas tank with the sender still in it , it was working when the tank was pulled .

 

size does matter. as well as the shape of the tank. ext cabs also had different tanks. I can't remember all the specifics, but I posted some time ago when I was researching one for mine.

 

This is where I plan on buying the wire.

I would rather rebuild the sender myself than try my luck at the slim pickens junkyard. New is too much money for a in my opinion. The nichrome wire is cheap $2-$5 shipped for 10ft.

I found a pretty good write-up on rebuilding senders here

 

Wow. Thanks shifty, I dug around as soon as I read this, got some stuff, but nothin like that. Might turn into a next week project..

 

I have a couple new ones I just was figuring to replace them when the fuel pump went. That was about 5 years ago.

I guess there is some difference in what is to expensive.

I had thought about rewinding them but it just was cheaper for me to buy new ones.

I just put in gas about every 120 miles or so

 

Well I pulled the sender lastnight and unwound the nichrome wire from its "board". It was frayed and broken up near "full" no doubt.

Specs:

Diemeter- .006"
Resistance (over 12")- 14.2 ohm's

The website I intend to order the nichrome from has it in the correct resistance but the diameter is .0031". Thats half the size of the OEM stuff. I was originally going to coat the bare wire in laquer before winding to keep the wraps from shorting on each other but now I may just manually maintain a hair of seperation between them. On the origianal they were wrapped tight, right up against each other in the middle of the "board". If I did this with the smaller diameter wire the resistance would double I believe.

I may try and find wire better mathched to the OEM Spec.

The arm that contacts the wire looks pretty worn too. My only concern is that it would wear through the thin metal and chafe the nichrome wire, eventually severing it. I think it will hold up for another 100K though.


I have pics but the camera was nearly dead so I left it at home.

 

and I thought me soldering new wires on my sender's connections was alot of work.

 

Yeah, this is more involved than I originally thought... The board is soldered to the sender as well.

 

One trick to help maintain separation is to wind TWO wires at the same time, keeping them neatly against each other. At the end, unwind and remove one of them, leaving you with a consistent .0031 spacing.

40 ohms/ft sounds awfully high for ~34 gauge Nichrome. http://www.wiretron.com/nicrdat.html Of course, measuring the resistance of a piece of wire is not easy; you may easily have had 20 ohms or so just in your connection method for the ohmmeter.

So before you start winding wire, you might consider hooking a potentiometer to the sensor line at the fuel tank, and measure the resistance when the potentiometer sets the fuel gauge to "exactly" F, and exactly E. I doubt getting the wire size the same is nearly as important as getting the total resistance to match the gauge.

 

Thanks for the tips. I will double check the resistance. I used emry cloth to remove the epoxy/laquer coating on the old wire and measured over a tape measure. The end of the wire was wrapped around one probe and the other just held against the bare wire. The resistance went up as I slid the probe along the wire.

EDIT: I meant 14.2 ohms/ft. I don't know how I got 40ohms.

I think there are specs in the FSM for the emty/full resistance readings. I will check.

 

If there are not, you can swap in different resistors between the gauge and ground until you find the right size ( resistance)for full and empty. You allready have ballpark figure. I have made test boxes for aircraft fuel gauges this way. The senders on small aircraft work the same way.
Never tried to rewind a sender though( to much liability ). You could always tell where someones average tank level was( thats where it would wear through).

 

subscribed

 

With your edit on the ohms/ft to 14.2, it sounds like you want the 34 gauge. Right diameter, and very close on the resistance.

Looks like the sender (spec) runs from 3 to 110 ohms. http://personal.utulsa.edu/~nathan-b.../6combinat.pdf You're going to have a tough time simulating 3 ohms, but a big-ole wire-wound power rheostat will probably be able to cover 0-150 ohms. You could just rewind your sender for 3-110 ohms, but since you've gone to this trouble you might want to see what will EXACTLY display E and F on YOUR gauge.

DO keep us posted.