new gas gauge still pegged full - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70blackfish · 11-07-2012, 12:58 AM

my trucks gas gauge was pegged on full, I unhook the wire from the sending unit, still reads way past full. SO I thought the fuel gauge was bad. install new one same things happens.....

what is it sending unit wire shorted out???

black_sheep454 · 11-07-2012, 10:29 AM

Sounds too me like it's grounded
Posted via Mobile Device

AirSpeed · 11-07-2012, 11:21 AM

Trace the wire from the dash to the tank, I bet it's shorted against the body somewhere, grounding it making it read full. Look under your sill plates, one of the screws holding it down may have pierced the wire.
Posted via Mobile Device

68K30 · 11-07-2012, 11:45 AM

Empty is 0 ohms=grounded;
Half is 44 ohms to ground;
Full is 88 ohms to ground
your sender wire is open between the gauge and sender

GMCJOE · 11-07-2012, 12:25 PM

You are grounded out somewhere for sure. Tracing the water is your best option, or just replace it. Grounding it out, it will read full. With unhooked it should read about a 1/3 of a tank ( I think). Simple fix.

JimKshortstep4x4 · 11-07-2012, 08:34 PM

68K30 has the information listed correctly. Try grounding the terminal on the fuse panel where the brown wire from the tank plugs in. It should go to empty with the key on.

Also, make sure the fuse that feeds the gas guage is good.

Jim

Husker · 11-08-2012, 06:34 PM

Good fuel guage reads about 90 ohms+- 5ohms or so unwired. Just checked. Wire from fuel sender unhooked from sender to ground should read approximatley the same, just checked also. I am checking all of this for a guy at worrk is having some problems with his. Radings may vary on temperature a bit. Hope this helps.
Ron

70blackfish · 11-19-2012, 09:28 PM

Thank you for the replays...it was a big air gap.....

11-07-2012, 12:58 AM	#1
70blackfish Registered User Join Date: Oct 2012 Location: Newhall CA Posts: 1,195	new gas gauge still pegged full my trucks gas gauge was pegged on full, I unhook the wire from the sending unit, still reads way past full. SO I thought the fuel gauge was bad. install new one same things happens..... what is it sending unit wire shorted out??? Attached Images

11-07-2012, 10:29 AM	#2
black_sheep454 Registered User Join Date: May 2011 Location: Lebanon, Mo. Posts: 1,315	Re: new gas gauge still pegged full Sounds too me like it's grounded Posted via Mobile Device __________________ 1968 chevy lwb, getting ready to join forces with the 70 gmc 1970 gmc swb, getting ready to be a 68 chevy swb 1971 gmc lwb 2500 2wd Sierra Grande 1988 chevy 1-ton crew cab 2wd waiting for a 12v cummins Last edited by black_sheep454; 11-07-2012 at 11:45 AM.

11-07-2012, 11:21 AM	#3
AirSpeed Registered User Join Date: Jul 2007 Location: Fall River California Posts: 2,026	Re: new gas gauge still pegged full Trace the wire from the dash to the tank, I bet it's shorted against the body somewhere, grounding it making it read full. Look under your sill plates, one of the screws holding it down may have pierced the wire. Posted via Mobile Device __________________ http://smg.photobucket.com/albums/v655/aaronhero/

11-07-2012, 11:45 AM	#4
68K30 Registered User Join Date: May 2007 Location: Pennsylvania Posts: 99	Re: new gas gauge still pegged full Empty is 0 ohms=grounded; Half is 44 ohms to ground; Full is 88 ohms to ground your sender wire is open between the gauge and sender

11-07-2012, 12:25 PM	#5
GMCJOE Registered User Join Date: Aug 2012 Location: Junction City, KS Posts: 782	Re: new gas gauge still pegged full You are grounded out somewhere for sure. Tracing the water is your best option, or just replace it. Grounding it out, it will read full. With unhooked it should read about a 1/3 of a tank ( I think). Simple fix. __________________ Joseph Joe's 69 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=543253 1969 GMC SWB-350 SBC 700R4 2013 Ram 2500 CC Laramie Longhorn Edition-6.7 PPEI EFI Live CSP5 5” ProFlo Exhaust

11-07-2012, 08:34 PM	#6
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: new gas gauge still pegged full 68K30 has the information listed correctly. Try grounding the terminal on the fuse panel where the brown wire from the tank plugs in. It should go to empty with the key on. Also, make sure the fuse that feeds the gas guage is good. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

11-08-2012, 06:34 PM	#7
Husker Registered User Join Date: Dec 1999 Location: Mid NE USA Posts: 2,212	Re: new gas gauge still pegged full Good fuel guage reads about 90 ohms+- 5ohms or so unwired. Just checked. Wire from fuel sender unhooked from sender to ground should read approximatley the same, just checked also. I am checking all of this for a guy at worrk is having some problems with his. Radings may vary on temperature a bit. Hope this helps. Ron __________________ Member #111 68 C-10 Daily Driver 70 4x4 Project 76 Jeep CJ-5 Help Support the Board: http://67-72chevytrucks.com/vboard/payments.php He who knows nothing is closer to the truth than he whose mind is filled with falsehoods and errors. Thomas Jefferson

11-19-2012, 09:28 PM	#8
70blackfish Registered User Join Date: Oct 2012 Location: Newhall CA Posts: 1,195	Re: new gas gauge still pegged full Thank you for the replays...it was a big air gap..... __________________ 69 SWB 780hp Hellcat powered, manual 6 speed, currie 9



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