Fuel Gauge reading wrong

[dank GN]

Make sure your gauges are grounded well . Mine did the same thing for a long time I would tap on it and it would rise and fall eventually getting to the correct level. Mine turned out yo be the actual gauge in the dash .

 

[Justin85]

This may be old but I just swapped out my OEM flex circuit board for a caspers flex board circuit and my gas gauge is very accurate now. Maybe the gauge was not getting a good connection anymore from the old Flex Board.

 

[GNICETRY]

This may be old but I just swapped out my OEM flex circuit board for a caspers flex board circuit and my gas gauge is very accurate now. Maybe the gauge was not getting a good connection anymore from the old Flex Board.

Are you talking about this?

Grand National 84-87 Analog Dash Flex-Board

107150 Grand National 84-87 Analog Dash Flex-BoardReplacement for # 25079363New and improved Flex-Board from the original obsolete version.Features: -Full Proof Alternator Circuit. -Includes Field Fix Feature built in the Board itself. Made with a special Kevlar Material sufficient fr

www.casperselectronics.com

 

[Justin85]

Are you talking about this?

Grand National 84-87 Analog Dash Flex-Board

107150 Grand National 84-87 Analog Dash Flex-BoardReplacement for # 25079363New and improved Flex-Board from the original obsolete version.Features: -Full Proof Alternator Circuit. -Includes Field Fix Feature built in the Board itself. Made with a special Kevlar Material sufficient fr

www.casperselectronics.com

Correct

 

[Vegas Turbo T]

I have the same problem. Gas gauge reads between 3/4 and 7/8 when full and has about 4-5 gallons when indicating empty. In my case it seems to be related to the 3 wire plug at the back bumper. I disconnected it and sprayed it with contact cleaner. It moved up to the correct reading and then slowly settled back to the incorrect reading. I was going to check Caspers to see if they sell the plugs and re-terminate the wires.

 

[earlbrown]

There's a design flaw with the factory sender. The float arm has a crappy ground connection because it just passes through a hole in the hanger assy. It's nowhere near a positive connection.

The fix is to solder a jumper wire from the arm to the hanger assy. After doing that to my car a few years ago, the sender resolution is so fast now, I can watch fuel slosh on the gauge.

 

[Vegas Turbo T]

Update: My initial problem is the gas gauge reading 1/8th low. When I fill the tank the gauge goes to 7/8th's. I bought a new sending unit and hooked it up and there was no change. Back to the drawing board.

 

[Vegas Turbo T]

I believe I found the smoking gun. After exhausting bad sender, damaged wires, loose connectors and loose grounds I went after the gauge. Wasn't too hard to remove. Just have to pop off the dash appliqué panel, it's held in by clips and pulls right off. Next remove the instrument glass (plastic), it's held on by 4 screws 7/32" socket I believe. Then there are 3 more screws to remove and the pictured assembly with the fuel gauge comes out.

What I found was the 3 pins on the back of the fuel gauge were loose. I used a 5/16" wrench and got about 3/4 of a turn on all 3 pins. The fuel gauge began reading correctly after I put it all together.

The 2nd photo shows the fuel gauge and RPM/boost indicator removed

 

[HotAirWH1]

When I ohm out the stock digital sending unit with a full tank I'm reading 348 ohm and not the 120 ohms that I'm suppose to read. After I drive the car and burn half a tank of fuel (9 gal.) My gas gauge will be at 15 gal. So I'm 6 gal off. I have a Digital Dash with a new Caspers Digital Dash Flex Plate. I have eliminated any loose or bad connections / grounds from the rear of the car to the dash. My plan is to fix using Earl Brown's solution or replace, if I can find an OE the digital sending unit this winter after the driving season ends. My question is - if I'm reading 348 ohms (full tank) at the sending unit - C320 (connection under the bumper to the tanks sending unit) could I temporarily install a 184 ohm resistor in parallel with the Pink Wire thus giving me the 120 ohms at the connector C320 and will this give me accurate readings on my fuel gauge as I burn gas. ???????