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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: SFP on July 22, 2016, 01:16:59 pm

Title: Fuel Gauge pinned past Full - '81 GMC 2500
Post by: SFP on July 22, 2016, 01:16:59 pm

Time to tackle first issue with the Farm Truck. 1981 GMC Sierra Grande 2500 Camper Special

The truck as dual tanks, and from research it would appear that both are 20 gallon tanks. Fuel selector works great. Fuel gauge, is pinned past Full for both tanks. At this point I am trying to figure out just how far I can get on a full tank. Starting with the drivers side tank.

Any advice on where to start with figuring out what's wrong? Should I just grab a new gauge and put that in?

Thanks in advance folks.

Scott

Title: Re: Fuel Gauge pinned past Full - '81 GMC 2500
Post by: Rattler12 on July 22, 2016, 03:54:37 pm

Direct short between the gauge and the tank sending unit or the wire is broken. Most schematics show it as a tan or blue wire. Mine in my 83 is pink.

Title: Re: Fuel Gauge pinned past Full - '81 GMC 2500
Post by: Irish_Alley on July 22, 2016, 04:11:18 pm

yours should be pink or tan or orange in color

Title: Re: Fuel Gauge pinned past Full - '81 GMC 2500
Post by: Burkhalter on July 22, 2016, 06:39:38 pm

I had that same issue in my 85 K10. It was a poor connection between the gauge and the printed circuit on the back of the instrument cluster.

However I'm not sure if 81 is before or after they went from the direct wiring to the printed wiring.

Title: Re: Fuel Gauge pinned past Full - '81 GMC 2500
Post by: VileZambonie on July 22, 2016, 07:55:36 pm

check that the sending unit connection is not disconnected.

Title: Re: Fuel Gauge pinned past Full - '81 GMC 2500
Post by: SFP on July 23, 2016, 01:17:59 pm

Thanks folks. Am going to try to get to it today or tomorrow and will let ya know. Am hoping it's just a disconnected wire or bad ground and not the actual units.

Title: Re: Fuel Gauge pinned past Full - '81 GMC 2500
Post by: SFP on August 18, 2016, 05:26:09 pm

SO anyone know how I know without getting them out if I have 2 point or 3 point sending units????

Title: Re: Fuel Gauge pinned past Full - '81 GMC 2500
Post by: hatzie on August 18, 2016, 10:05:52 pm

Quote from: VileZambonie on July 22, 2016, 07:55:36 pm

check that the sending unit connection is not disconnected.

Or the tank ground wire is broken.

Sent from my SM-P605V using Tapatalk

Title: Re: Fuel Gauge pinned past Full - '81 GMC 2500
Post by: Militiaman55 on August 21, 2016, 01:20:34 pm

Quote from: SFP on August 18, 2016, 05:26:09 pm

SO anyone know how I know without getting them out if I have 2 point or 3 point sending units????

I'm not sure what they are calling "points", but on my 74 with a carbureted 350 there are two tubes/ports exiting each sender.  One is the fuel line, the other is a vent line. I believe the fuel injected models have three tubes/ports to incorporate a return fuel line. 

Title: Re: Fuel Gauge pinned past Full - '81 GMC 2500
Post by: Spool on February 23, 2017, 10:12:05 am

Quote from: Burkhalter on July 22, 2016, 06:39:38 pm

I had that same issue in my 85 K10. It was a poor connection between the gauge and the printed circuit on the back of the instrument cluster.

However I'm not sure if 81 is before or after they went from the direct wiring to the printed wiring.

Did you have to replace the printed circuit to fix the issue?