Author Topic: Fuel gauge stopped working  (Read 156 times)

hedonastik

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Fuel gauge stopped working
« on: November 10, 2019, 10:01:52 PM »
Hi all,

I started my '69 Z/28 for the 1st time in 2 months and discovered that the previously working fuel gauge was now reading as over full.
IE; the needle is as far to the right as it can go and doesn't move, despite there being only a half tank of fuel in it.
Has anyone encountered this before?

Regards.

rich69rs

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Re: Fuel gauge stopped working
« Reply #1 on: November 10, 2019, 10:05:49 PM »
Stuck float? Short to ground somewhere in the wiring?
Richard Thomas
1969 RS

hedonastik

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Re: Fuel gauge stopped working
« Reply #2 on: November 10, 2019, 10:15:16 PM »
OK, so it's mechanical or electrical, sounds terrific.

Thanks

TangoBravo

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Re: Fuel gauge stopped working
« Reply #3 on: November 11, 2019, 12:33:29 AM »
Check for a loose, disconnected ground on the fuel tank sender. Also check for a disconnected brown sender wire at the fuel sender or at the gauge. Both conditions will send the fuel needle past full. Be certain you have a good ground at the gauge panel.

169INDY

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Re: Fuel gauge stopped working
« Reply #4 on: November 11, 2019, 01:09:32 AM »
"Tango Bravo" has is correct but let's expand on the troubleshooting steps.

1) Assure you have not overfilled the unit.   (*Total joking :) )

1a) Open the trunk and inspect the Brown (Tan) wire that is connected via in line connector near the latch support. Where it penetrates  the trunk floor. For grins disconnect and clean (Isopropyl Alcohol or Deoxit 5)   &  inspect connections both the Packard Series 56 terminals and the plastic connector male and female plugs.  and reconnect using a small blade screw driver. (Recheck gauge operations.
& /or
1b) While this connection is disconnected get a (VOM) Volt Ohm Meter digital or analog and set to resistance and test the wire that goes down thru the trunk floor to the sender ie. (tan- brown) thru the variable resistor to ground. Expected range in Ohms is 0-90ohms.  100 ohms to Infinity will cause dash gauge to indicate way full indication thus it overdrives dash gauge past full. Zero ohms should drive the gauge to Empty & 45 ohms appx 1/2 etc.

If no continuity to ground is found;
2) Jack up car secure etc &  Remove Right (Pass) Rear tire.
3) Inspect the grounding connection of the circuit the black ground wire from the sender soldered or crimped to the body of the sender-pickup assembly.  The lug is terminated at the right side gas tank strap forward hinge point. Remove the sheet metal screw, clean and polish the lug and the body for good ground surface interface, Inspect the wire and lug barrel for broken strand or corrosion etc.

If no ground found after verifying termination;
4) Try to determine the 90 degree molded connection is secure on the top pin of the sender. This is Very difficult to do with the rear end, muffler & tank in place. This may require "DROPPING" the tank.

These two areas are the predominate areas of concern;

Next up would be the trunk wiring extension inline connection in the driver side qtr and issues under the dash related to the connection or further inline connections to the gauge or the 12VDC hot supply (Pink) Additionally the gage ground as TB stated.

Start aft (easy areas then work your way forward.)

I have a pegged gauge on my 68 right now (* I have been playing Fuel Tank Lotto for a while and got stranded once) & I have narrowed it down to the Back of the car by using a Fuel Tank Simulator I made.

JIM
Jim
68 SS/RS L35 Th-400 LOS
69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS

169INDY

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Re: Fuel gauge stopped working
« Reply #5 on: November 11, 2019, 02:21:58 AM »
Tech reference
Jim
68 SS/RS L35 Th-400 LOS
69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS

BULLITT65

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Re: Fuel gauge stopped working
« Reply #6 on: November 11, 2019, 03:14:21 AM »
I had this happen on my white 69. ( it actually was like that when I bought it). I took the sender apart and realized the resistor had reached the end. I had to rebuild the unit with a new resistor.
Not recommended, but if you're handy and have patience it can be done. I liked knowing I was able to re-install the original, and it is back to being spot on, after who knows how many years.
1969 garnet red Z/28 46k mile unrestored X77
-Looking for 3192477 (front) spiral shocks 3192851 (rear)
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