Fuel Gauge Problem - Need Your Help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

rn2fine · 01-03-2008, 08:18 PM

I have a 72 with a 3 gauge cluster. My fuel gauge is not working correctly. When the tank is full it shows 1/4 and empty when it is empty. It slowly creeps down from 1/4 to empty as I use gas so I know that a float is not stuck in the tank. The problem is likely electrical based on my not so experienced thoughts. Any ideas on where to start or how to resolve?

70 GMC Trucker · 01-03-2008, 08:27 PM

Are you sure your float isn't full of fuel because of a small leak ??

**WorkinLonghorn** · 01-03-2008, 09:01 PM

Yeah it's real easy to take it out and check the float and the operation of the unit,especially with an Ohm meter. When you disconnect the leed to the tank sender the fuel gauge should read past full IIRC. If it does then you either have a bad float,bad sender,or the float arm is not raising all the way up for some reason.

lbpd719 · 01-03-2008, 09:55 PM

I just ordered the parts from a vendor here on the board (Thanks GMCPaul) to fix this exact problem.

Let me guess, you have not had the truck for some time or it was sitting on empty for some time... You filled it and "Look ma it works!". Then over time, it started to not get as close to full as you would have liked. then it started hanging out in the middle..

I am betting the float.. pull the wire behind the cab and see if it goes up to past full, then ground it. Full range of motion there for the gague? Its your time then. pull it and enjoy your leaky float. Get your repair hardware from them as well. Great people to deal with. Even over the phone

northerngmc · 01-04-2008, 07:34 AM

Try this trouble shooting guide..

http://www.6066gmcguy.org/Electrical-02.htm

72freak · 01-04-2008, 07:47 AM

I have replaced many sending units in these trucks and one thing I always do is remove the stock float...I think its brass and I replace it with a plastic one.
I have had 2 new ones...one that came from the board vendor you bought yours from that leaked when it was new!!!!

It was no fault of the vendor......they just re-sell them....but Ill take sealed plastic over brazed together brass any day!!!!

01-03-2008, 08:18 PM	#1
rn2fine Registered User Join Date: Jan 2004 Location: Arizona Posts: 157	Fuel Gauge Problem - Need Your Help I have a 72 with a 3 gauge cluster. My fuel gauge is not working correctly. When the tank is full it shows 1/4 and empty when it is empty. It slowly creeps down from 1/4 to empty as I use gas so I know that a float is not stuck in the tank. The problem is likely electrical based on my not so experienced thoughts. Any ideas on where to start or how to resolve? __________________ 72 C10 Burb 350 700R4 70 C20 LWB 350 Crate TH400 68 Chevelle

01-03-2008, 08:27 PM	#2
70 GMC Trucker Registered User Join Date: Apr 2007 Location: Victoria, BC Canada Posts: 48	Re: Fuel Gauge Problem - Need Your Help Are you sure your float isn't full of fuel because of a small leak ??

01-03-2008, 09:01 PM	#3
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,861	Re: Fuel Gauge Problem - Need Your Help Yeah it's real easy to take it out and check the float and the operation of the unit,especially with an Ohm meter. When you disconnect the leed to the tank sender the fuel gauge should read past full IIRC. If it does then you either have a bad float,bad sender,or the float arm is not raising all the way up for some reason. __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, 2nd owner, Work-Truck supreme. Best $300 I ever spent.

01-03-2008, 09:55 PM	#4
lbpd719 Zappaphile! Join Date: Apr 2007 Location: Los Banos, California Posts: 228	Re: Fuel Gauge Problem - Need Your Help I just ordered the parts from a vendor here on the board (Thanks GMCPaul) to fix this exact problem. Let me guess, you have not had the truck for some time or it was sitting on empty for some time... You filled it and "Look ma it works!". Then over time, it started to not get as close to full as you would have liked. then it started hanging out in the middle.. I am betting the float.. pull the wire behind the cab and see if it goes up to past full, then ground it. Full range of motion there for the gague? Its your time then. pull it and enjoy your leaky float. Get your repair hardware from them as well. Great people to deal with. Even over the phone __________________ 1969 C20 LWB Camper Special - The Beater.. 1998 Cheyenne V6 - 4/6 Drop - For The Son

01-04-2008, 07:34 AM	#5
northerngmc Registered User Join Date: Jan 2004 Location: Whitehorse YK Canada Posts: 2,651	Re: Fuel Gauge Problem - Need Your Help Try this trouble shooting guide.. http://www.6066gmcguy.org/Electrical-02.htm __________________ Blaine 59 GMC 9314 a.k.a. Whoopee 68 C20 50th Anniversary a.k.a. The Rat http://www.flickr.com/photos/northerngmc/ http://www.members.tripod.com/P-wee/index_032.htm 1.61803 is one H of a lot better than 3.14159, no really it is!

01-04-2008, 07:47 AM	#6
72freak Rottenwood Garage Member Join Date: May 2005 Location: Marietta, Georgia Posts: 4,321	Re: Fuel Gauge Problem - Need Your Help I have replaced many sending units in these trucks and one thing I always do is remove the stock float...I think its brass and I replace it with a plastic one. I have had 2 new ones...one that came from the board vendor you bought yours from that leaked when it was new!!!! It was no fault of the vendor......they just re-sell them....but Ill take sealed plastic over brazed together brass any day!!!! __________________ 2004 Chevrolet Suburban C1500 2001 Chevrolet 2500HD Crew 6.0 1999 Harley Davidson Electra Glide 1972 Chevrolet C-20 Custom Camper "Dump Truck" 1972 Chevrolet C-20 Suburban "Big Green" 1969 Chevrolet C-50 Wedge Hauler "Leonidis" 1966 C-10 2x4 short fleet 327 4 speed "Race Truck" 1952 Plymouth Cranbrook "Rican" (my grandfathers) 1931 Ford Model A Coupe "Black Beauty" 1930 Ford Model A truck "Club Cab" 4x4 Rottenwood Garage and Speed Shop.....where everything must be racy! *It's not just a hobby..It's a LIFESTYLE!!!* Thanks for nothing Barrett-Jackson You cant fix stupid or teach accountability! Time wasters, looky Lous and tire kickers are everywhere!



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