Well it seems that my fuel gauge is nonfunctioning. The cheapest new sending unit I could find is around $250, so Im curious what generally goes wrong with the senders when they fail (corrosion on resistors, shorting?), and if they are repairable. Since Im replacing my gas tank and pump anyway, Im going to try to repair the sender while its out of the car. Any tips?

 

The resistor is wirewound. The wiper is plated spring steel. The connections are resistance welded. There really isn't much there. If you get it out and it looks repairable, repair it, but test it before you install it in the tank. The most difficult part may be removing the plastic surrounding the resistor and reassembling it. If the wirewound resistor is broken, you may have difficulty unless you have a lot of patience and some very fine SS wire to rewind it.

Does the guage read full scale or zero?

 

Much appreciated Vader, invaluable advise.

The gauge no longer moves at all, its stuck at nearly zero; for awhile it would work intermittantly, but no longer. I suppose it could be hung up in the tank, but my guess was that since the car sits during the winter, and my cheap *ss hardly ever has the tank over 1/4 full, the contact points on the sender somehow got corroded after being exposed to moisture and rarely being contacting the by wiper. Maybe Im way off base. Do you think it could be something else?

Also, will I be able to test the sender by just using a multimeter on the connection and verifying that the resistance changes uniformly as the wiper moves?

Thanks.

 

I had similar issues on a tank and sending unit from the junk yard.

I pulled the pum and sending unit.

I hooked an ohm meeter to the sender wires and got no change when I swung the float arm.

Took the sending unit apart.

The point(s) and coiled wire were corroded.

I cleaned them with a pencil eraser and also the wire where the point(s) make contact.

Did get noticable difference in the ohm gage after that.

Do not know if is is accurate as I do not know what the range should be but it did give repeatable results.

Have not put back in car as it will be in a race car so i do not know the effect on the gague.

I was experiminting with an ohm meeter and that was the purpose of me cleaning the points.

I was just playing around, but it did seem to make the sender work

 

Ok, thanks for the tips.

 

I'll verify the "rebuildability" of the senders. Same deal as above poster...wound wire, plus the contact that rubs on it.

My gauge was actually off by about 50%, cleaning it all up got me to within about 10-20% accurate...still reads overfull at full, and is empty before it hits E, but not by much.

Much better than being 50% off, and worth it based on cost of new.

If it never moves, make sure that everything going to the gauge itself is good. I can't recall how the whole thing is wired, but there is only one wire for the gauge from the tank.

You should be able to ground the wire from the tank to gauge and peg the gauge out one way or another. If not, the sender isn't the issue. Since it never moves at all, (you should see something when the key comes on if there is power to the gauge) I would suspect the sender ISN'T the issue, unless it truly is stuck, which is almost impossible unless the in-tank baffles break and hit it.

 

So if the signal wire is grounded, does that cause the gauge to read full or empty?

I ask because I just had a shop replace my fuel pump, and the fuel gauge is now pegged at "full." It never had any problems before. The shop is trying to tell my that since it was so old and corroded that probably the sending unit itself got stuck while they were working on it. I find that hard to believe since it never, ever had a problem before. I am more inclined to believe that they pinched the sending unit wire when reinstalling the tank. But my theory would be invalid if grounding the wire causes an "empty" reading.

Thanks for any help provided.

 

Should go to full when grounded.

 

Okay, that turns out to be right. In a stunning display of doing what's right, the shop owner took it upon himself to pull the tank again and check out the connections and wiring. Sure enough, a solder joint had failed (or more likely, it got pulled apart when they dropped the tank) and the resulting disconnection sent the gauge to "full." Problem solved, and props to Auto Express in Bellaire, Texas for solving a problem they could have blown off. I'm sure glad I didn't have to pull that tank twice!