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#1 |
Registered User
Join Date: May 2007
Location: East Haven, CT
Posts: 882
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Fuel guage suddenly reading 1/2 empty with a full tank
My truck in signature below has a new odd issue. Today I was at about 1/4 tank of fuel so I filled up. Started up and drove away. Gauge now only reads 1/2 empty. Gauge always worked properly. Unless maybe I missed the rest of the gas and poured it on the ground.... no that didn't happen.
What are some simple things to check for? I am hoping it is not the sending unit in the tank..... I've had this tank dropped twice for two failed pumps, I'd like to not drop it again. The last pump was replaced months ago so I know it wasn't the pump install that affected the gauge readings. It's a dual 16gal tank 1987 swb 305
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87 Chevy 2wd SWB: 305/700r4 Dual Exhaust, K&N Filter, Injector Pod Spacer, TBI Spacer, Belltech Front Sway Bar, Corvette Servo, Western Chassis 4/6 and c-notch |
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#2 |
Robert Olson Transport
![]() Join Date: Oct 2002
Location: recent transplant to NC USA
Posts: 20,287
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Re: Fuel guage suddenly reading 1/2 empty with a full tank
ground on the tank? does the other side work ok?
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Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!! |
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#3 |
Registered User
Join Date: Oct 2009
Location: Manchaca, TX
Posts: 45
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Re: Fuel guage suddenly reading 1/2 empty with a full tank
Would a bad ground cause the tank to read way past full...both sides do it, they both go back to empty when the key is off. When the key is on they both race up to way past full??
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77 Scottsdale,.454 .30 over, 10:1 flat top pistons, 480 lift comp cam, 781 heads stock valve size, some no name polished aluminumn dual plane intake advised by my machine shop to match the cam(He said is was great lol) Holley 750 vac sec, Turbo 400 built raybestos clutches and Kolene steels, Eaton Posi 3:73 14 bolt ![]() |
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#4 |
Registered User
Join Date: Nov 2007
Location: Franklin Indiana
Posts: 635
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Re: Fuel guage suddenly reading 1/2 empty with a full tank
Guys what you may be seeing is the effect that sulfur in the fuel has on the resistor in the tank. Cheap gas is high in sulfur try adding techron to a few tanks and see if it clears up. Here is a copy of a post from a Corvette Forum where there have been a lot of these issues
#1 cause sulfur build up on the sending unit from using gas with insufficient detergent package.... Use a good fuel system cleaner like Techron fuel system cleaner ( NOT the injector cleaner) , Seafoam. Berrymans Chemtool B-12, Valvoline Synpower fuel system cleaner for a coule tank fulls and switch to a top tier gasoline www.toptiergas.com #2. corroded ground for the sending unit #3. bad sending unit
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My Truck's not leaking its marking its territory! |
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#5 | |
Registered User
Join Date: Oct 2009
Location: Manchaca, TX
Posts: 45
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Re: Fuel guage suddenly reading 1/2 empty with a full tank
Quote:
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77 Scottsdale,.454 .30 over, 10:1 flat top pistons, 480 lift comp cam, 781 heads stock valve size, some no name polished aluminumn dual plane intake advised by my machine shop to match the cam(He said is was great lol) Holley 750 vac sec, Turbo 400 built raybestos clutches and Kolene steels, Eaton Posi 3:73 14 bolt ![]() |
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#6 |
Registered User
Join Date: Dec 2007
Location: Palmer, Alaska
Posts: 13,821
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Re: Fuel guage suddenly reading 1/2 empty with a full tank
if the circuit is open, broken wire or no ground, it will read way past full like yours is and drop to empty with the key off. If it is the same for both tanks, I would check your tank changing switch.
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#7 |
Registered User
Join Date: Jul 2009
Location: Clearviller PA
Posts: 50
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Re: Fuel guage suddenly reading 1/2 empty with a full tank
mine is reading right above quarter tank when full but still moves to empty as it uses fuel...
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#8 | |
Registered User
Join Date: Aug 2009
Location: Prescott MI
Posts: 8
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Re: Fuel guage suddenly reading 1/2 empty with a full tank
Quote:
I put in a new sending unit and made sure ground was good at frame and it is still only reading Quarter tank when full?? I guess i will have to try a new guage ![]() |
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