Sticking Fuel Gauge

Larrybrook · 12-17-2013, 02:35 PM

My fuel gauge 'sticks' on empty, but if you tap it a little, it jumps to the accurate position and usually stays there for a while. My car sat for about 15 years before I got her back on the road, and I don't drive her all that often. I have cleaned all the spade connections from the sender to the gauge, but it's still a little fussy. Is it a big chore to take it apart and try cleaning inside the gauge? will this even make a difference?

Anyone tackled this before?

Larrybrook · 12-17-2013, 02:46 PM

Okay AFTER I posted this I found a few threads that indicate it is most likely the sender unit. Is it just a coincidence that when i tap the gauge it works again?

pors1968 · pors1968's Garage

That mean Inside of your sender the float does not travel on dirty wire.It cost nothing to clean the Inside carfully.

ossiblue · 04:35 PM

Quote:

Originally Posted by Larrybrook

Okay AFTER I posted this I found a few threads that indicate it is most likely the sender unit. Is it just a coincidence that when i tap the gauge it works again?

I'm going to offer a challenge to that conclusion. If your sending unit is not producing the correct resistance to the fuel gauge--because of a sticky float or gunked up wires--it will not get "fixed" by you tapping on the gauge itself. I suspect the gauge needle pivot is a bit dirty and is getting stuck when power is sent to the gauge and a tapping is freeing the pivot. The reason the gauge reads accurately once it's freed is because it is getting the proper resistance reading from the sender. In addition, your fuel gauge is in a spot where moisture often condenses inside the gauge. It would not be unusual for a bit of moisture, combined with dust over the years, may have caused a problem with a free moving needle.

porwolf · 12-17-2013, 04:57 PM

I successfully cleaned out my pretty messed up 79SC sender unit after sitting 16 years in a half full tank of fuel. It is not too difficult a job. The important thing is to be very careful with cleaning the inside. The sender unit works with an internal float that ride up and down with the fuel level. On the side of the float there are very fine vertical resistance wires. The float has some small bronze blades that ride the wire and create the resistance equivalent to the float position. An easy way to test the fuel sender function is to remove the sending unit from the tank and measure the resistance while holding the unit horizontally and moving it to make the float go up and down inside the unit. If the float does not give the right resistance it's time to open up the unit and rebuild it. There are several threads here on how to do that. Saves $130.- for a new sending unit.

Larrybrook · 12-19-2013, 02:37 PM

You make a good argument, I may start with the gauge. I've read a couple of posts and getting them apart doesn't seem too difficult. I assume contact cleaner should get rid of any dust, should it be followed by a squirt of WD40 on the pivot needle?

Larrybrook · 12-19-2013, 02:38 PM

Note: my car is in storage for the winter so I have a lot of time to tinker with this.

Dodge Man · Dodge Man's Garage

My new sender had the same problem. I cleaned it and just removed the unit to cycle it back & forth. After 20 minutes of inverting back & forth the sender quit sticking. You probably have a dirt/debris problem where mine was a metal or plastic burr.