Fuel gauge issues

[CES 3245th]

1983 AM General M923A1

Fuel gauge needle is jumping back and forth.
Is it that the fuel gauge is no good or is there something else that could be causing the Needle to go to the left and to the right rapidly?

Any advice or help would be greatly appreciated thank you in advance

 

[Valor]

1983 AM General M923A1

Fuel gauge needle is jumping back and forth.
Is it that the fuel gauge is no good or is there something else that could be causing the Needle to go to the left and to the right rapidly?

Any advice or help would be greatly appreciated thank you in advance

Mine does that too when the tank gets low. I have an M923A2. I think it's normal, just the fuel sloshing around in the tank and moving the float up and down. When the tank is full, the gauge reads steady.

 

[Ajax MD]

Ha, mine only jumps around when the fuel level is high.

 

[71DeuceAK]

MV fuel gauges are known to lie more than (insert politician of your choice you don't like). Always worth carrying a dip stick...

 

[CES 3245th]

MV fuel gauges are known to lie more than (insert politician of your choice you don't like). Always worth carrying a dip stick...

 

[Bill Nutting]

I had this issue on my M934. It was the sending unit causing it. Here is how I tested it. First I installed a new ground wire from the frame to the sending unit. Then I connected a 10 ohm resistor from ground to the wire that goes to the gauge (at the tank with the sending unit disconnected). I drove the truck with the resistor in place and the needle did not bounce. This told me the wire and gauge were good. I replaced the sending unit and now my gauge is stable. Up until now I had to rely on dipping the tank. My 80 gallon tank reads 14” when full. So it is 5.7 gallons per inch. I didn’t throw out my dip stick because it is the most actuate way to measure the fuel level. It’s just a bit hard to do while driving down the road...

 

[simp5782]

The newer tube type sending units are the way to go with a replacement over the float arm type

 

[ldmack3]

Go tap on the sensor and tank next to it. I have 2 tanks and one is allover the place. If I tap on the tank next to it, the needle jumps around. Moving the wire does nothing so either a bad connection in the tank or a bad sensor.

 

[Bill Nutting]

The newer tube type sending units are the way to go with a replacement over the float arm type

Now you have my interest. I was not aware that there was some other type of sending unit. I had a hard time finding a replacement unit. The one I found is a float type much like the original unit. What does the newer one look like?

 

[CES 3245th]

I had this issue on my M934. It was the sending unit causing it. Here is how I tested it. First I installed a new ground wire from the frame to the sending unit. Then I connected a 10 ohm resistor from ground to the wire that goes to the gauge (at the tank with the sending unit disconnected). I drove the truck with the resistor in place and the needle did not bounce. This told me the wire and gauge were good. I replaced the sending unit and now my gauge is stable. Up until now I had to rely on dipping the tank. My 80 gallon tank reads 14” when full. So it is 5.7 gallons per inch. I didn’t throw out my dip stick because it is the most actuate way to measure the fuel level. It’s just a bit hard to do while driving down the road...

Good info thank you

 

[simp5782]

Now you have my interest. I was not aware that there was some other type of sending unit. I had a hard time finding a replacement unit. The one I found is a float type much like the original unit. What does the newer one look like?

Goes off tank depth for which one you need for the square setups.


They work with 12/24. I always replace my gauge and sender together. Just habit.

Ultimate Fuel Senders

Serving the heavy duty truck and trailer industry as a manufacturer and marketer of air, hydraulic and electrical components and systems. Driven to be Better

tectran.com

 

[Bill Nutting]

Goes off tank depth for which one you need for the square setups.


They work with 12/24. I always replace my gauge and sender together. Just habit.

Ultimate Fuel Senders

Serving the heavy duty truck and trailer industry as a manufacturer and marketer of air, hydraulic and electrical components and systems. Driven to be Better

tectran.com

Thanks Wes. I’m not sure how I would make these work in my 14” tank. They have a 10” unit then jump to 17” . Our beloved and grossly inaccurate M series gauges go from 0 ohms to I think 40 ohms. So you would have to replace the gauge to match these units. Now I have to measure the tank in my M37 to see if they have one that fit it... Thanks for the lead. I don’t know what is worse, a gauge that is dead or one that reads wrong...