'72 GMC Jimmy fuel guage problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

longbowdude · 02-25-2003, 07:46 PM

The sending unit on my Jimmy was changed by my father shortly before I bought the truck from him and there is still a problem. The guage pegws itself at the 3 o'clock position and doesn't accurately show the fuel level. Do I need to change the sending unit again or is this more likely an electrical problem??

JimKshortstep4x4 · 02-25-2003, 07:55 PM

If you unplug the sender, the gauge should read well past full. If you ground the brown wire from the sender, then the gauge should read empty. If that is the case then the problem is in the sender unit, sender grounding or the wire from the back to the front. The sender actuates the dash gauge by "grounding" it in effect, so if the sender is not grounded completely then the gauge can end up anywhere.

An easy location to do your gauge tests is at the fuse panel as the wire from the sender plugs into the panel.

Jim

longbowdude · 02-25-2003, 08:00 PM

Thanks Jim,
You probably just saved me an entire weekend of troubleshooting.

da-burb · 02-25-2003, 08:03 PM

I just had the same problem with my snow plow truck. I turned out to be the wire between the fuse box and the sending unit. I replaced it and now I have the option to run out of gas on purpose.

Longhorn Man · 02-25-2003, 11:39 PM

Common place for that wire to short out is under the chrome trim at the bottom of the door.

02-25-2003, 07:46 PM	#1
longbowdude Registered User Join Date: Aug 2002 Location: Texas Posts: 5	'72 GMC Jimmy fuel guage problem The sending unit on my Jimmy was changed by my father shortly before I bought the truck from him and there is still a problem. The guage pegws itself at the 3 o'clock position and doesn't accurately show the fuel level. Do I need to change the sending unit again or is this more likely an electrical problem?? __________________ 1972 GMC Jimmy 4X4 350/TH350/NP205

02-25-2003, 08:00 PM	#3
longbowdude Registered User Join Date: Aug 2002 Location: Texas Posts: 5	sending unit Thanks Jim, You probably just saved me an entire weekend of troubleshooting. __________________ 1972 GMC Jimmy 4X4 350/TH350/NP205

02-25-2003, 08:03 PM	#4
da-burb "Ochre Ogre" Join Date: Apr 2000 Location: Springfield, MN Posts: 3,558	I just had the same problem with my snow plow truck. I turned out to be the wire between the fuse box and the sending unit. I replaced it and now I have the option to run out of gas on purpose. __________________ Bowtie Truck Stop Inc. Mid-West GM Truck Restoration Parts Supplier Your Key Parts, Auto Metal Direct, Dynacorn, and Goodmark dealer. like us @ www.facebook.com/BowtieTruckStop 1971 C-10 Suburban (Ochre) 1971 K-10 Suburban (Ochre) 1972 C-10 Suburban (Ochre) 1972 K-20 Suburban (Yellow- that just aint right!) Springfield, Minnesota 56087

02-25-2003, 07:55 PM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	If you unplug the sender, the gauge should read well past full. If you ground the brown wire from the sender, then the gauge should read empty. If that is the case then the problem is in the sender unit, sender grounding or the wire from the back to the front. The sender actuates the dash gauge by "grounding" it in effect, so if the sender is not grounded completely then the gauge can end up anywhere. An easy location to do your gauge tests is at the fuse panel as the wire from the sender plugs into the panel. Jim

02-25-2003, 11:39 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Common place for that wire to short out is under the chrome trim at the bottom of the door.



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