Mechanics

FUEL GAUGE

1999 GMC Yukon

Electrical problem
1999 GMC Yukon 6 cyl Four Wheel Drive Automatic 86000 miles

I just purchased this used Yukon, and was happy to see the dealer filled the gas tank. But after 200 miles of highway travel and the gauge was still reading full.
I decided to stop and fill the tank to see just what was happening. It took 20 gallons, and now the gauge was reading EMPTY. Strange? After about 50 miles and a moderate bump the gauge went to FULL, more bumps more empties and fulls, until it finally settled at full. I refilled the tank after 300 miles and same thing all over.
At first I thought loose wire. But then it would read correctly when making connection and either full or empty when open.
Now I'm guessing sensor in tank, so how do you change that?
thanks for your time and expertese
JON

updated 4-8-09
Very good reply, very detailed. Although I don't think I'm up to that much work. Do you think my guess is correct or could it be something else? I'm going to be 70 in June and can't do a lot of physical stuff but I am very experienced electrical trouble shooting and repair.
Thanks again for your time.
Avatar
JonVan
April 7, 2009.



Procedures below are for hte 5.7L and 7.4L engines, let me know if your engine size is different.

REMOVAL: Disconnect the negative battery cable.
Relieve the fuel system pressure.
Drain the fuel tank and remove the tank.
Remove the fuel sender assembly.
Disconnect the fuel pump electrical connector.
Remove the fuel level sensor electrical connector retaining clip.
Disconnect the fuel level sensor electrical connector from under the fuel sender cover.
Remove the fuel level sensor retaining clip.
Squeeze the locking tangs and remove the fuel level sensor.

INSTALLATION: Install the fuel level sensor.
Install the fuel level sensor retaining clip.
Connect the fuel level sensor electrical connector.
Connect the fuel level sensor electrical connector retaining clip.
Connect the fuel pump electrical connector.
Install the fuel sender assembly.
Refill the fuel tank.
Install the fuel filler cap.
Connect the negative battery cable.

Inspect for leaks: Turn the ignition switch ON for 2 seconds.
Turn the ignition switch OFF for 10 seconds.
Turn the ignition switch ON.
Check for fuel leaks.

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