fuel gauge issue - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GMC Guy · 01-22-2011, 11:55 PM

so i went to fill my tank the other day, and the pump shut off like the tank is full. but the gauge only went to a little over 3/4 full. tried filling the other tank, same thing. gauge only goes up to a little over 3/4 full. this just started, never had an issue in the past. anyone have any suggestions? i sure would like to know how much gas i have left lol

79gmcc15 · 01-23-2011, 04:40 AM

Subscribin and a bump!
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sixshooter798 · 01-23-2011, 04:43 AM

Does it stay in the same place no matter what?

GMC Guy · 01-23-2011, 04:45 PM

no the gauge goes down, it just won't go all the way to full. which is annoying cuz i don't know exactly how much fuel i have...

it has to be something wrong with the gauge or the connections to it right? cuz it does the same thing which ever tank i fill.

tucsonjwt · 01-23-2011, 10:41 PM

My fuel gauge had the problem at the other end - would only go to 1/4 full on both tanks, then would start working when the tanks were actually 1/4 full. My guess is you need a fuel gauge like I needed one - $50 + shipping will answer your question for sure.

GMC Guy · 01-23-2011, 10:42 PM

Quote:

Originally Posted by tucsonjwt

My fuel gauge had the problem at the other end - would only go to 1/4 full on both tanks, then would start working when the tanks were actually 1/4 full. My guess is you need a fuel gauge like I needed one - $50 + shipping will answer your question for sure.

where did you buy yours? and maybe i'll try a few from the pick n pull

sixshooter798 · 01-24-2011, 02:12 AM

I'd grab a couple from the local junkyard before I bought a new one. The gauge does sound like your problem!

GMC Guy · 01-24-2011, 03:26 AM

is there any way of testing a fuel gauge without filling the tank?

tucsonjwt · 01-24-2011, 07:24 AM

Classic Parts. In Tucson, you would never find a used gauge at a junkyard, and if you did it would cost almost as much as a new one.

justinburnett · 01-24-2011, 10:26 AM

Pretty sure if you ground out your sending wire it should read full. Mine was always full because I had a short in the wire. Replaced it and it worked. Now my other side is still saying always full and I haven't figured out the problem with that one yet but at least the one works.

GMC Guy · 01-24-2011, 02:54 PM

Quote:

Originally Posted by justinburnett

Pretty sure if you ground out your sending wire it should read full. Mine was always full because I had a short in the wire. Replaced it and it worked. Now my other side is still saying always full and I haven't figured out the problem with that one yet but at least the one works.

which wire do i ground out? just a few more details on how to "ground it out" sorry not the electrician lol

i might go to the junkyard today and grab like 4-5, and tell the guy at the counter i need find one that works and will return the others.

GmtGmt · 01-24-2011, 03:36 PM

dont think its your fuel gauge but i might be your filler it self seach back a pages for how to pump fuel or something like that its a common problem on the early square bodys

joe231 · 01-24-2011, 03:43 PM

These are 0-90 ohm senders. An open circuit (infinite resistance) will read past full and a short to ground (zero ohms resistance) will read empty. If both tanks are acting the same it must be something they both have in common such as the selector switch or the gauge.
I'm leaning towards the gauge....
Posted via Mobile Device

justinburnett · 01-24-2011, 05:14 PM

Yeah, in retrospect, there's almost no way for both sides to go wrong exactly the same at the same time so.... I'd say gauge too. As for the wires, I think it's blue for the left and brown with a white stripe on the right but you'd have to look at what color wire actually goes up to the tank for sure and then pick that color going into the back of the switch in the cab.

Maybe I was backwards on which way they read though. What would cause "infinite resistance"? a completely disconnected wire or... ?

GMC Guy · 01-24-2011, 05:32 PM

well i just got back from pick n pull, about to swap the gauge and fill a tank. i'll let you guys know what happens

GMC Guy · 01-25-2011, 01:35 PM

turns out not to be the fuel gauge. but the connection from the circuit board. i really am tired of dealing with bad connections due to a 30+ year old circuit board...i really want to buy a new one ($70) but i think i should give pick n pull another try. they had a bunch on 78-80 clusters out there, so hopefully one will work better than mine

justinburnett · 01-27-2011, 05:33 PM

any luck yet?

Turns out I was wrong. both my tanks are messed up. Wiring seems to be all good but the right tank says 1/4 full and its filled to the top, and the left one say way over full and it's bone dry. I give up. Taking it to a shop on monday and telling them to fix it. May just have 'em replace everything from the sending units all the way up to the fuel gauge itself. I need to get this done and put the cab back together cause it's a damned wreck in there.

GMC Guy · 01-27-2011, 08:30 PM

ya it was a bad connection from the sender to the gauge. so i just went ahead and hard wired the fuel gauge, along with the voltmeter and oil pressure gauge while i was at it. works flawlessly now

TruAggression · 01-27-2011, 09:47 PM

Im having an issue where it reads i have a 1/4 tank ive switched with 3 gauges that i have lying around and one other reads the same 1/4 full and another goes like way past full by an inch or so.... You say you hard wired it?How? mines a 87 is mine different ? i also would like to know how much gas i have in it.

GMC Guy · 01-28-2011, 01:05 AM

there's three connections that need to be made on the back of the gauge.
1. a switched 12 volt source
2. ground
3. and a connection from the sending unit. this usually is 2 pink wires on in the main harness connection to the gauge cluster. (at least mine was)

01-22-2011, 11:55 PM	#1
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	fuel gauge issue so i went to fill my tank the other day, and the pump shut off like the tank is full. but the gauge only went to a little over 3/4 full. tried filling the other tank, same thing. gauge only goes up to a little over 3/4 full. this just started, never had an issue in the past. anyone have any suggestions? i sure would like to know how much gas i have left lol __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

01-23-2011, 04:40 AM	#2
79gmcc15 Gettin It One Pice At A Time Join Date: Oct 2004 Location: everett, washington Posts: 2,688	Re: fuel gauge issue Subscribin and a bump! Posted via Mobile Device __________________ RIP ELJAY Work In Progress 1979 GMC C1500 Trailering Special. Getting the truck done, one piece at a time. “You can tell a lot about a fellow’s character by his way of eating jellybeans.”Ronald Reagan “I don’t know the key to success but I know the key to failure is trying to please everybody.” Bill Cosby

01-23-2011, 04:43 AM	#3
sixshooter798 Desert Rat Join Date: Jul 2010 Location: Mojave Desert Posts: 169	Re: fuel gauge issue Does it stay in the same place no matter what?

01-23-2011, 04:45 PM	#4
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: fuel gauge issue no the gauge goes down, it just won't go all the way to full. which is annoying cuz i don't know exactly how much fuel i have... it has to be something wrong with the gauge or the connections to it right? cuz it does the same thing which ever tank i fill. __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

01-23-2011, 10:41 PM	#5
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,195	Re: fuel gauge issue My fuel gauge had the problem at the other end - would only go to 1/4 full on both tanks, then would start working when the tanks were actually 1/4 full. My guess is you need a fuel gauge like I needed one - $50 + shipping will answer your question for sure.

01-24-2011, 02:12 AM	#7
sixshooter798 Desert Rat Join Date: Jul 2010 Location: Mojave Desert Posts: 169	Re: fuel gauge issue I'd grab a couple from the local junkyard before I bought a new one. The gauge does sound like your problem!

01-24-2011, 03:26 AM	#8
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: fuel gauge issue is there any way of testing a fuel gauge without filling the tank? __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

01-24-2011, 07:24 AM	#9
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,195	Re: fuel gauge issue Classic Parts. In Tucson, you would never find a used gauge at a junkyard, and if you did it would cost almost as much as a new one.

01-24-2011, 10:26 AM	#10
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	Re: fuel gauge issue Pretty sure if you ground out your sending wire it should read full. Mine was always full because I had a short in the wire. Replaced it and it worked. Now my other side is still saying always full and I haven't figured out the problem with that one yet but at least the one works.

01-24-2011, 03:43 PM	#13
joe231 Registered User Join Date: Dec 2007 Location: Palmer, Alaska Posts: 13,821	Re: fuel gauge issue These are 0-90 ohm senders. An open circuit (infinite resistance) will read past full and a short to ground (zero ohms resistance) will read empty. If both tanks are acting the same it must be something they both have in common such as the selector switch or the gauge. I'm leaning towards the gauge.... Posted via Mobile Device __________________ *CHEVY ONLY* Last edited by joe231; 01-24-2011 at 03:44 PM.

01-24-2011, 05:14 PM	#14
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	Re: fuel gauge issue Yeah, in retrospect, there's almost no way for both sides to go wrong exactly the same at the same time so.... I'd say gauge too. As for the wires, I think it's blue for the left and brown with a white stripe on the right but you'd have to look at what color wire actually goes up to the tank for sure and then pick that color going into the back of the switch in the cab. Maybe I was backwards on which way they read though. What would cause "infinite resistance"? a completely disconnected wire or... ?

01-24-2011, 05:32 PM	#15
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: fuel gauge issue well i just got back from pick n pull, about to swap the gauge and fill a tank. i'll let you guys know what happens __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)] Last edited by GMC Guy; 01-24-2011 at 05:33 PM.

01-25-2011, 01:35 PM	#16
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: fuel gauge issue turns out not to be the fuel gauge. but the connection from the circuit board. i really am tired of dealing with bad connections due to a 30+ year old circuit board...i really want to buy a new one ($70) but i think i should give pick n pull another try. they had a bunch on 78-80 clusters out there, so hopefully one will work better than mine __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

01-27-2011, 05:33 PM	#17
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	Re: fuel gauge issue any luck yet? Turns out I was wrong. both my tanks are messed up. Wiring seems to be all good but the right tank says 1/4 full and its filled to the top, and the left one say way over full and it's bone dry. I give up. Taking it to a shop on monday and telling them to fix it. May just have 'em replace everything from the sending units all the way up to the fuel gauge itself. I need to get this done and put the cab back together cause it's a damned wreck in there.

01-27-2011, 08:30 PM	#18
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: fuel gauge issue ya it was a bad connection from the sender to the gauge. so i just went ahead and hard wired the fuel gauge, along with the voltmeter and oil pressure gauge while i was at it. works flawlessly now __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]



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01-27-2011, 09:47 PM	#19
TruAggression Registered User Join Date: Aug 2010 Location: Las Vegas,NV Posts: 118	Re: fuel gauge issue Im having an issue where it reads i have a 1/4 tank ive switched with 3 gauges that i have lying around and one other reads the same 1/4 full and another goes like way past full by an inch or so.... You say you hard wired it?How? mines a 87 is mine different ? i also would like to know how much gas i have in it.

01-28-2011, 01:05 AM	#20
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: fuel gauge issue there's three connections that need to be made on the back of the gauge. 1. a switched 12 volt source 2. ground 3. and a connection from the sending unit. this usually is 2 pink wires on in the main harness connection to the gauge cluster. (at least mine was) __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)] Last edited by GMC Guy; 01-28-2011 at 01:07 AM.

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