fuel gauge reading

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Beast496

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Fallon, Nevada
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Ron
Truck Year
1985
Truck Model
Sierra K3500
Engine Size
496
Hey all, tried searching for this one, but couldn't find exactly what it could be except for possibly a resistor issue. 85' K3500 with both left and right saddle fuel tanks were initially working as advertised. Gauge was reading accurate, switch was working, everything, etc. Then, one day, I went and filled both tanks, and when i got in the truck and started it up, the gauge only went to 1/4 tank, on both sides. Fuel level seems to correlate correctly from there, if you picture 1/4 tank as the new full lol. In other words, 1/4 =full tank, 1/8 = 1/2 tank, 1/16 =1/4 tank and so on. Again, this is for both sides. Was gonna start digging into it but wanted to see if anyone has had this problem before I do. Thanks.
 

Jgonick

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Joel
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1985
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K10
Engine Size
350
I would start by checking terminals on back of gauge. Make sure the nuts tight. There is also the resistor on the back of the gauge that might be going bad (flat piece between two terminals) . Newer gauges have the resistor built in.


this video shows where the resistor is located at about 2:40 min
diag non-functioning fuel gauge
 
Last edited:

Beast496

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Location
Fallon, Nevada
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Ron
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1985
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Sierra K3500
Engine Size
496
I would start by checking terminals on back of gauge. Make sure the nuts tight. There is also the resistor on the back of the gauge that might be going bad (flat piece between two terminals) . Newer gauges have the resistor built in.


this video shows where the resistor is located at about 2:40 min
diag non-functioning fuel gauge
Thank you. I’m 99% sure it’s a resistor and this video makes finding where it is a piece of cake. Much appreciated.
 

Jgonick

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350
I'm guessing the gauge, but it wouldn't hurt to also check all the pink wire's connection points.
 

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Dukester68

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Arizona
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Gary
Truck Year
1986
Truck Model
c2500
Engine Size
350
I would start by checking terminals on back of gauge. Make sure the nuts tight. There is also the resistor on the back of the gauge that might be going bad (flat piece between two terminals) . Newer gauges have the resistor built in.


this video shows where the resistor is located at about 2:40 min
diag non-functioning fuel gauge
Can you purchase a new resistor anywhere sir?? Thank you
 

mcarlo86

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1990
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Suburban
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Hey all, tried searching for this one, but couldn't find exactly what it could be except for possibly a resistor issue. 85' K3500 with both left and right saddle fuel tanks were initially working as advertised. Gauge was reading accurate, switch was working, everything, etc. Then, one day, I went and filled both tanks, and when i got in the truck and started it up, the gauge only went to 1/4 tank, on both sides. Fuel level seems to correlate correctly from there, if you picture 1/4 tank as the new full lol. In other words, 1/4 =full tank, 1/8 = 1/2 tank, 1/16 =1/4 tank and so on. Again, this is for both sides. Was gonna start digging into it but wanted to see if anyone has had this problem before I do. Thanks.
My dad had an '83 K20 that was just like that. My brother @cmichels83 has that pickup now. I am pretty sure it is the resistor behind the fuel gauge.
 

cmichels83

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Fargo
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Craig
Truck Year
1983
Truck Model
K10
Engine Size
350
My dad had an '83 K20 that was just like that. My brother @cmichels83 has that pickup now. I am pretty sure it is the resistor behind the fuel gauge.
Yeah, I had a spare cluster and just took the fuel gauge out of that and plugged it into my cluster and it read the correct fuel level. I should do a post sometime soon on my cluster rebuild with aftermarket gauges shoe horned in.
 

Jgonick

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K10
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Can you purchase a new resistor anywhere sir?? Thank you
I'm not sure-
The ceramic resistor, If I remember correctly should be ~ 90 ohms. You might be able to find a used one on Ebay etc.

However a new fuel gauge (that won't need the resistor) is usually around $50

LMC-example_LINK
 

Beast496

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Sierra K3500
Engine Size
496
Thank you all for the help. To update, my truck was down for a couple months while I had the transmission out to rebuild it. I finally got it all put back together and went to fill up the truck and now the gauge doesn't come off of empty, lol. So, I'm now 100% positive it's the gauge/resistor. I'll get in there at somepoint here soon and check, or just replace the gauge. By chance, does anyone have a spare fuel gauge sitting around for an 81-87? Big fuel gauge.
 

Dukester68

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Location
Arizona
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Gary
Truck Year
1986
Truck Model
c2500
Engine Size
350
I'm guessing the gauge, but it wouldn't hurt to also check all the pink wire's connection points.
Does anyone know if this tank valve and meter switch can be removed and repaired?? Cleaned??
 

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