Fuel gauge won't show full - The 1947 - Present Chevrolet & GMC Truck Message Board Network

YellowMenace · 01-31-2005, 03:42 PM

I've searched and found some wierd fuel gauge problems, but didn't see this one. Gauge seems to work, except that it shows between 1/4 and 1/2 tank when it is actually full. It goes down proportionally from there as the tank empties.

Will show full when key is turned off. Replaced the sender and fixed the previous problem (pierced float). Tries old sender manually and it does the same thing. I'm sure it's in the gauge itself.

Any ideas.

mtdave2 · 01-31-2005, 04:07 PM

i fought with mine for a while too. i went thru 3 floats, not sure what i was doing but they all broke. finaly i got a good one.. id pull the sending unit again, and connect the wire (away front the tank) and manualy move it too the full position, then you can see if the gauge is the prob or not.

JimKshortstep4x4 · 01-31-2005, 04:40 PM

If you have checked the sending unit output when the tank is full and the ohm reading is 90 ohms then it is probably the resistor on the back of the gauge.

A quick check of the resistor can be made by checking across the posts with the gauge disconnected for resistance from the wiring harness. It should read approximately 35 ohms.

Jim

jhow66 · 01-31-2005, 07:24 PM

This should help with your problem:
www.fix-a-gauge.com

Blue Beard · 01-31-2005, 09:37 PM

Good link, I have three trucks with gauge issues..

Tim240Z · 01-31-2005, 10:03 PM

I had that problem too. Found that the float had a pin hole in it, so it had gasoline in it. Put a new plastic one in and have no problems since.
Tim

01-31-2005, 03:42 PM	#1
YellowMenace Registered User Join Date: Jul 2004 Location: Katy, TX (Houston) Posts: 73	Fuel gauge won't show full I've searched and found some wierd fuel gauge problems, but didn't see this one. Gauge seems to work, except that it shows between 1/4 and 1/2 tank when it is actually full. It goes down proportionally from there as the tank empties. Will show full when key is turned off. Replaced the sender and fixed the previous problem (pierced float). Tries old sender manually and it does the same thing. I'm sure it's in the gauge itself. Any ideas.

01-31-2005, 04:07 PM	#2
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,508	i fought with mine for a while too. i went thru 3 floats, not sure what i was doing but they all broke. finaly i got a good one.. id pull the sending unit again, and connect the wire (away front the tank) and manualy move it too the full position, then you can see if the gauge is the prob or not. __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban

01-31-2005, 07:24 PM	#4
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	This should help with your problem: www.fix-a-gauge.com __________________ 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

01-31-2005, 09:37 PM	#5
Blue Beard Registered User Join Date: Jan 2003 Location: Washington State Posts: 8,834	Good link, I have three trucks with gauge issues.. __________________ 1970 Chev CST 2003 Harley Fatboy 1975 Chevrolet Step Van 1956 Chev Bel Air 1977 Blazer 2WD For Sale $3000.00 1978 Blazer 2WD For Sale $7000.00 1978 Silverado 2005 Monte Carlo

01-31-2005, 10:03 PM	#6
Tim240Z Senior Member Join Date: Jan 2005 Location: LAX area, So Cal Posts: 499	I had that problem too. Found that the float had a pin hole in it, so it had gasoline in it. Put a new plastic one in and have no problems since. Tim __________________ 1972 Suburban C20 454/TH700R4, eaton-corporate 4.10 (looking for 3.7) Sold: 71 Cheyenne 20 Installed a 99 5.7L L31/4L60E from Suburban 1500 (2005)

01-31-2005, 04:40 PM	#3
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	If you have checked the sending unit output when the tank is full and the ohm reading is 90 ohms then it is probably the resistor on the back of the gauge. A quick check of the resistor can be made by checking across the posts with the gauge disconnected for resistance from the wiring harness. It should read approximately 35 ohms. Jim

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