why dont my fuel gauge work - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jordon johnson · 07-24-2005, 10:10 PM

most of these trucks ive owned the gas gauge never works whats the prob with it most of the time?

Prerunner1982 · 07-24-2005, 10:20 PM

usually a ground at the sending unit at the tank...

jordon johnson · 07-24-2005, 11:31 PM

ok thanks i will check

DBLSPRT68 · 07-25-2005, 10:04 AM

Jordon, my gas gauge problem turned out to be the gauge itself. I put new sending units in and made sure the ground was good, still nothing

. I put in a completely different tach cluster, and when I put the battery back on, IT MOVED! The gas gauge moves!, and I switched tanks(dual tank) and the other tank reads too! It was like Christmas.......I now know how much gas is in my tanks

! If all else fails, change the gauge. David

86-C10-V6 · 07-25-2005, 01:09 PM

Gas guages usually don't work correctly for the same reason most of the guages eventually have trouble.
The calibration resistor on the back of the guage develops oxidation that eventually causes the resistor to loose contact with the guage terminals.
If you remove the guage you will see a white block of ceramic being held on with thin metal pressed nuts. This ceramic block is the calibration resistor and it makes electrical connection through the pressed nuts to the studs which are the guage terminals.
If you remove the nuts and the resistor, you can clean the resistor with a pencil eraser. The contact surfaces should be brite and shiny.
Check the resistor with a ohm meter, it should be 90 ohms.
Re-install the resistor and the guage.
These guages use two coils to drive the guage, the coil with the calibration resistor drives the guage to the right, the coil with the sensor i.e. oil pressure sender, gas tank sending unit, themperature sender will drive the guage to the left, towards zero or empty.
Normally when the guage resistor is making poor contain, the gas guage will read 1/4 tank when full, but will move lower as the tank becomes empty. With the oil pressure and temperature guage, it will always read low.
I am posting this from memory but I believe this is correct.
If your calibration resistor is bad, reads open, you can make one from resistors from radio shack, just know that the exisiting resistor is rated 5 watts so you will need something fairly large to replace it, I used 2 180 ohm 2 watt resistors tied together.
Hope this helps.

jordon johnson · 07-25-2005, 02:19 PM

thanks to everyone now i have a lot of checking to do....

07-24-2005, 10:10 PM	#1
jordon johnson Registered User Join Date: Mar 2004 Location: austin ky Posts: 104	why dont my fuel gauge work most of these trucks ive owned the gas gauge never works whats the prob with it most of the time? __________________ 94 cobra!!!!!!LOL 90 gmc 4x4 ext cab swb 355 6in lift blue 85 4x4 lwb 350 4spd red 87 1/2 ton 2wd lwb 305 th350 red83 1/2 ton 4wd lwb ---- 700r4

07-24-2005, 10:20 PM	#2
Prerunner1982 Registered User Join Date: Oct 2002 Location: Edmond, OK Posts: 5,904	usually a ground at the sending unit at the tank... __________________ Jon 1982 Chevy Silverado 350/th350.... RETIRED 1993 Jeep XJ 2 door(Cherokee) 4wd 4.0ltr/AX-15 (5spd)/NP231 .... Oklahoma Roll Call

07-24-2005, 11:31 PM	#3
jordon johnson Registered User Join Date: Mar 2004 Location: austin ky Posts: 104	ok thanks i will check __________________ 94 cobra!!!!!!LOL 90 gmc 4x4 ext cab swb 355 6in lift blue 85 4x4 lwb 350 4spd red 87 1/2 ton 2wd lwb 305 th350 red83 1/2 ton 4wd lwb ---- 700r4

07-25-2005, 10:04 AM	#4
DBLSPRT68 Registered User Join Date: Nov 2000 Location: Ft. Mill, SC USA Posts: 931	Jordon, my gas gauge problem turned out to be the gauge itself. I put new sending units in and made sure the ground was good, still nothing . I put in a completely different tach cluster, and when I put the battery back on, IT MOVED! The gas gauge moves!, and I switched tanks(dual tank) and the other tank reads too! It was like Christmas.......I now know how much gas is in my tanks ! If all else fails, change the gauge. David __________________ PROJECT TRUCK: 1985 SWB C10 Silverado Black/Charcoal, 1990 V2500 Suburban, 2018 Suburban, 2005 GMC 2500HD CCSB, 2014 Toyota Camry SE, HAD.....1968 Camaro RS/SS Family owned since new; 350 3 speed SOLD

07-25-2005, 01:09 PM	#5
86-C10-V6 Shadetree Mechanic Join Date: Oct 2002 Location: Youngsville, NC Posts: 100	Calibration resistor on the guage Gas guages usually don't work correctly for the same reason most of the guages eventually have trouble. The calibration resistor on the back of the guage develops oxidation that eventually causes the resistor to loose contact with the guage terminals. If you remove the guage you will see a white block of ceramic being held on with thin metal pressed nuts. This ceramic block is the calibration resistor and it makes electrical connection through the pressed nuts to the studs which are the guage terminals. If you remove the nuts and the resistor, you can clean the resistor with a pencil eraser. The contact surfaces should be brite and shiny. Check the resistor with a ohm meter, it should be 90 ohms. Re-install the resistor and the guage. These guages use two coils to drive the guage, the coil with the calibration resistor drives the guage to the right, the coil with the sensor i.e. oil pressure sender, gas tank sending unit, themperature sender will drive the guage to the left, towards zero or empty. Normally when the guage resistor is making poor contain, the gas guage will read 1/4 tank when full, but will move lower as the tank becomes empty. With the oil pressure and temperature guage, it will always read low. I am posting this from memory but I believe this is correct. If your calibration resistor is bad, reads open, you can make one from resistors from radio shack, just know that the exisiting resistor is rated 5 watts so you will need something fairly large to replace it, I used 2 180 ohm 2 watt resistors tied together. Hope this helps. __________________ Dave M. (Hacksaw) 86 C10 Scottsdale LWB, 4.3L, Edelbrock 1904, K&N, 700R4, 3.08 Auburn Performance 89 GMC S-15 Extended Cab 4x4, 4.3L, FI 98 K1500 Xcab, 5.7L, 3.43 Gov-Lok

07-25-2005, 02:19 PM	#6
jordon johnson Registered User Join Date: Mar 2004 Location: austin ky Posts: 104	thanks to everyone now i have a lot of checking to do.... __________________ 94 cobra!!!!!!LOL 90 gmc 4x4 ext cab swb 355 6in lift blue 85 4x4 lwb 350 4spd red 87 1/2 ton 2wd lwb 305 th350 red83 1/2 ton 4wd lwb ---- 700r4



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