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Fuel gauge issues

CES 3245th

Member
102
0
16
Location
Boston Ma
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

Active member
196
215
43
Location
Apple Valley, Ca.
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.
 

Bill Nutting

Well-known member
Steel Soldiers Supporter
573
1,284
93
Location
Chesterfield, Mi.
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

Feo, Fuerte y Formal
Supporting Vendor
12,125
9,384
113
Location
Mason, TN
The newer tube type sending units are the way to go with a replacement over the float arm type
 

ldmack3

Well-known member
Steel Soldiers Supporter
849
1,740
93
Location
N. Central Idaho
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

Well-known member
Steel Soldiers Supporter
573
1,284
93
Location
Chesterfield, Mi.
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

Member
102
0
16
Location
Boston Ma
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

Feo, Fuerte y Formal
Supporting Vendor
12,125
9,384
113
Location
Mason, TN
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.

 

Bill Nutting

Well-known member
Steel Soldiers Supporter
573
1,284
93
Location
Chesterfield, Mi.
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.

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...😜
 
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