Gas Gauge HELP! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

lookingtobuy · 07-15-2007, 11:21 AM

Good morning all!!

The gas gauge on my 72 is always on empty.The garage I took it to said the
gauge is bad so I bought an aftermarket-- still reads empty.

I followed the brown wire from the tank to the fuse block and when i unplugged it the old gauge went to full. Plug it back in and it goes to empty.
I KNOW the the tank in full.

Any suggestions before I start cracking beers this early in the A.M.

Thanks in advance!!!

**zeusflash** · 07-15-2007, 03:02 PM

Your in dash gauge is fine. Either your sender is bad or the float on the sender has a hole in it. The float is usually the culprit in my experiance. Either way the bad news is the fuel tank has to come out...sorry!

tom71 · 07-15-2007, 04:13 PM

check the ground for the sender before you drop the tank

lookingtobuy · 07-15-2007, 05:29 PM

thangs four yur halp -- 8 bears lateter i wil tri it

just kidding--- i went off and did other things. I will put it back together
and run out the tank. Then I can check the sending unit>

69TowRig · 07-15-2007, 11:37 PM

I would unplug the wire where it plugs into the sending unit and see if it pegs the needle. If it does, you have a short to ground in the sending unit. If it stays at "empty" then you have a short somewhere between the sending unit and the fuse panel. And then the last option, the float has "sunk" and needs to be repaired or replaced. I have repaired mine before with solder plugs, they don't last long so it is best to get a new float or an entire sending unit.

lookingtobuy · 07-16-2007, 06:28 PM

Thanks everyone, I believe its the sending unit, gotta drive for awhile to empty the tank. I just ordered a new one so it should be good to go!!

DURRTY · 07-17-2007, 02:16 AM

just crack the beers and start unbolting things...... the more beers the more gets done :P

lookingtobuy · 07-25-2007, 05:25 PM

Hi again

Ok, I unplug the tank wire from the fuse block and the gage pegs.
I unplug the wire from the sending unit and it pegs.
I buy a new sending unit and find that the original float has a hole in it
(thats why it was always on "E")

So I install the new sender, reinstall the tank and sand the frame and bolt back in the ground bolt, put everything back together and fill the tank.

The gage only goes slightly above 1/4 (WTF? I say out loud)
Wiggle this wiggle that nothing, unplug the wire to the sender and the gage pegs.

IT looks like I've got a bad sender-- any ideas before I tear it apart again????

Thanks, John

**zeusflash** · 07-25-2007, 09:36 PM

I hate to have to say this but you probably have a bad gauge. I just went through this last weekend on a buddys 72 Blazer. Dropped the tank,changed the sender,reinstalled the tank.....filled with gas....gauge reads just over 1/4 tank.....wiggle poke,prod,hit,swear.....everything looks good...it should be working!!!!!!

Well,only one thing left....the gauge. Dug around in the old spare parts bins,found another gauge,pulled cluster,installed gauge,reinstalled cluster....(drum roll please as I turn the key)....TADA..gauge works.

(Yes,I tested the old sender with an ohmmeter before replacing the old one...it was dead...the old double failure..I love those!)

lookingtobuy · 07-26-2007, 09:13 AM

Hello, are there any tests I can to before taking it all apart again??

Thanks for your help!!!!

jhow66 · 07-27-2007, 12:42 AM

Quote:

Originally Posted by lookingtobuy

Hello, are there any tests I can to before taking it all apart again??

Thanks for your help!!!!

Yes -
www.fix-a-gauge.com

lookingtobuy · 07-27-2007, 08:47 AM

Hi jhow66,

I just sent off an email to the fix-a-gauge co. Their website is a little vague
Do you have experience with them and what is it that they do /offer/sell??
Thanks again!!!!

jhow66 · 07-27-2007, 11:23 AM

The thing that goes wrong with the gauge is the small white resistor on back of gauge on the 2 posts. If you have an another gauge (just about any year) take it off and try it before ordering one.

69TowRig · 07-27-2007, 12:18 PM

You can buy the OEM style resistor from the Truck Shop for $10:

http://www.truckandcarshop.com/trucks60_72/t60_034.html

gringoloco · 07-27-2007, 01:58 PM

Quote:

Originally Posted by lookingtobuy

Hello, are there any tests I can to before taking it all apart again??

Thanks for your help!!!!

Stole this from the FAQ:

Quote:

Originally Posted by VetteVet

fuel gauge--32ohms post to post on both
left to ground 65 ohms right to ground 63 ohms

You can also check your sender to be sure it is giving the correct resistance. With a full tank, you should have ~90ohms from the brown sender wire to ground, 0ohms@empty.

lookingtobuy · 07-27-2007, 02:12 PM

Thanks for everyones help,

TOOO hot and humid here in NH to do anything I'll try over the weekend and report back!!

lookingtobuy · 07-28-2007, 04:41 PM

Thanks to everyone for your help, I went and got a resistor from a donor
gas gauge and IT WORKED! The old one tested with no continuity!

I know the sending unit was bad because the float had holes in it!

The troubleshooting tips helped, and the resistor was the problem!

Thanks

**Yukon Jack** · 07-30-2007, 09:30 AM

Glad you got it figured out!

07-15-2007, 11:21 AM	#1
lookingtobuy Registered User Join Date: Sep 2006 Location: Northeast Posts: 159	Gas Gauge HELP! (Revised) Good morning all!! The gas gauge on my 72 is always on empty.The garage I took it to said the gauge is bad so I bought an aftermarket-- still reads empty. I followed the brown wire from the tank to the fuse block and when i unplugged it the old gauge went to full. Plug it back in and it goes to empty. I KNOW the the tank in full. Any suggestions before I start cracking beers this early in the A.M. Thanks in advance!!! Last edited by lookingtobuy; 07-28-2007 at 04:37 PM.

07-15-2007, 03:02 PM	#2
zeusflash Senior Member Join Date: Feb 2005 Location: Post Falls,Idaho Posts: 691	Re: Gas Gauge HELP! Your in dash gauge is fine. Either your sender is bad or the float on the sender has a hole in it. The float is usually the culprit in my experiance. Either way the bad news is the fuel tank has to come out...sorry! __________________ '69 3/4 ton 427 CST Pickup '71 CST Blazer '72 GMC 3/4 4x4

07-15-2007, 04:13 PM	#3
tom71 what happened to flint mi Join Date: Oct 2005 Location: san diego Posts: 437	Re: Gas Gauge HELP! check the ground for the sender before you drop the tank __________________ 71 swb 2wd fleet frame off in progress 72 4x4 blazer daily driver 70 olds cutlass s mint condition owned by a grandma 56 gmc 2wd project waitng 97 fiance mobile

07-15-2007, 05:29 PM	#4
lookingtobuy Registered User Join Date: Sep 2006 Location: Northeast Posts: 159	Re: Gas Gauge HELP! thangs four yur halp -- 8 bears lateter i wil tri it just kidding--- i went off and did other things. I will put it back together and run out the tank. Then I can check the sending unit>

07-15-2007, 11:37 PM	#5
69TowRig Senior Member Join Date: Jan 2005 Location: Raleigh, NC Posts: 894	Re: Gas Gauge HELP! I would unplug the wire where it plugs into the sending unit and see if it pegs the needle. If it does, you have a short to ground in the sending unit. If it stays at "empty" then you have a short somewhere between the sending unit and the fuse panel. And then the last option, the float has "sunk" and needs to be repaired or replaced. I have repaired mine before with solder plugs, they don't last long so it is best to get a new float or an entire sending unit. __________________ -Chris Building a stripper, one part at a time: 1969 K5, 307, 3spd, 3 seats, hard top. Added Pwr Discs, Pwr Steering, Aux Battery, T-case Skid, Lighted Sidemarkers, HEI, Lock-Right Diff, ECE Class IV Hitch, 32" MT/Rs. Parts to Install: Hand Throttle, Console, Tow Hooks, Dual Horns, AM-FM, Dealer Swing-Away Tire Carrier, Gas Tank Skid. Also building a 1950 Willys CJ-3A and off-roading a 2001 Nissan Frontier on 1-Ton Portals...

07-16-2007, 06:28 PM	#6
lookingtobuy Registered User Join Date: Sep 2006 Location: Northeast Posts: 159	Re: Gas Gauge HELP! Thanks everyone, I believe its the sending unit, gotta drive for awhile to empty the tank. I just ordered a new one so it should be good to go!!

07-17-2007, 02:16 AM	#7
DURRTY USMC Join Date: May 2007 Location: SLc,UT Posts: 300	Re: Gas Gauge HELP! just crack the beers and start unbolting things...... the more beers the more gets done :P __________________ Semper Fi

07-25-2007, 05:25 PM	#8
lookingtobuy Registered User Join Date: Sep 2006 Location: Northeast Posts: 159	Re: Gas Gauge HELP! Hi again Ok, I unplug the tank wire from the fuse block and the gage pegs. I unplug the wire from the sending unit and it pegs. I buy a new sending unit and find that the original float has a hole in it (thats why it was always on "E") So I install the new sender, reinstall the tank and sand the frame and bolt back in the ground bolt, put everything back together and fill the tank. The gage only goes slightly above 1/4 (WTF? I say out loud) Wiggle this wiggle that nothing, unplug the wire to the sender and the gage pegs. IT looks like I've got a bad sender-- any ideas before I tear it apart again???? Thanks, John

07-25-2007, 09:36 PM	#9
zeusflash Senior Member Join Date: Feb 2005 Location: Post Falls,Idaho Posts: 691	Re: Gas Gauge HELP! I hate to have to say this but you probably have a bad gauge. I just went through this last weekend on a buddys 72 Blazer. Dropped the tank,changed the sender,reinstalled the tank.....filled with gas....gauge reads just over 1/4 tank.....wiggle poke,prod,hit,swear.....everything looks good...it should be working!!!!!! Well,only one thing left....the gauge. Dug around in the old spare parts bins,found another gauge,pulled cluster,installed gauge,reinstalled cluster....(drum roll please as I turn the key)....TADA..gauge works. (Yes,I tested the old sender with an ohmmeter before replacing the old one...it was dead...the old double failure..I love those!) __________________ '69 3/4 ton 427 CST Pickup '71 CST Blazer '72 GMC 3/4 4x4

07-26-2007, 09:13 AM	#10
lookingtobuy Registered User Join Date: Sep 2006 Location: Northeast Posts: 159	Re: Gas Gauge HELP! Hello, are there any tests I can to before taking it all apart again?? Thanks for your help!!!!

07-27-2007, 08:47 AM	#12
lookingtobuy Registered User Join Date: Sep 2006 Location: Northeast Posts: 159	Re: Gas Gauge HELP! Hi jhow66, I just sent off an email to the fix-a-gauge co. Their website is a little vague Do you have experience with them and what is it that they do /offer/sell?? Thanks again!!!!

07-27-2007, 11:23 AM	#13
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Re: Gas Gauge HELP! The thing that goes wrong with the gauge is the small white resistor on back of gauge on the 2 posts. If you have an another gauge (just about any year) take it off and try it before ordering one. __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

07-27-2007, 12:18 PM	#14
69TowRig Senior Member Join Date: Jan 2005 Location: Raleigh, NC Posts: 894	Re: Gas Gauge HELP! You can buy the OEM style resistor from the Truck Shop for $10: http://www.truckandcarshop.com/trucks60_72/t60_034.html __________________ -Chris Building a stripper, one part at a time: 1969 K5, 307, 3spd, 3 seats, hard top. Added Pwr Discs, Pwr Steering, Aux Battery, T-case Skid, Lighted Sidemarkers, HEI, Lock-Right Diff, ECE Class IV Hitch, 32" MT/Rs. Parts to Install: Hand Throttle, Console, Tow Hooks, Dual Horns, AM-FM, Dealer Swing-Away Tire Carrier, Gas Tank Skid. Also building a 1950 Willys CJ-3A and off-roading a 2001 Nissan Frontier on 1-Ton Portals...

07-27-2007, 02:12 PM	#16
lookingtobuy Registered User Join Date: Sep 2006 Location: Northeast Posts: 159	Re: Gas Gauge HELP! Thanks for everyones help, TOOO hot and humid here in NH to do anything I'll try over the weekend and report back!!

07-28-2007, 04:41 PM	#17
lookingtobuy Registered User Join Date: Sep 2006 Location: Northeast Posts: 159	Re: Gas Gauge HELP! Thanks to everyone for your help, I went and got a resistor from a donor gas gauge and IT WORKED! The old one tested with no continuity! I know the sending unit was bad because the float had holes in it! The troubleshooting tips helped, and the resistor was the problem! Thanks



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07-30-2007, 09:30 AM	#18
Yukon Jack Post Whore Join Date: Feb 2000 Location: Rose Hill, KS, USA Posts: 12,683	Re: Gas Gauge HELP! Glad you got it figured out! __________________ 1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14

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