Fuel Gauge - never quite full

[DuctTape]

I stood there and watched until the gas was within sight of the top of the channel, and the gauge makes it to not showing full. This was while still sitting at the pump.

 

Gauge issue? Faulty or bad connection? Bad ground? OPEC scam? 
 

(Maybe related, after displaying correctly the temp gauge sometimes shoots to the top and then shortly after drops into correct position. Do these share a common ground maybe?)
 

Any help is appreciated.

Edited July 26 by DuctTape

[John76]

Yes, these are common problems that can easily be fixed (usually!).

You have too much resistance in the fuel sender wire, or the ground wire. This causes the gauge to read low.

Clean these connections carefully and add an additional ground wire to the sender if needed.

I cleaned everything and still could not stop the fuel gauge from bouncing when I used the right turn signal. Adding an additional wire solved the problem.

Also, add a ground wire to the 2 gauge connections (fuel and temp) on the back of your dash pod.

 

 

 

[Henning]

Well, the glass seems to be half full.

And what is more: it isn't half empty.

 

henn

[DuctTape]

1 hour ago, John76 said:

Yes, these are common problems that can easily be fixed (usually!).

You have too much resistance in the fuel sender wire, or the ground wire. This causes the gauge to read low.

Clean these connections carefully and add an additional ground wire to the sender if needed.

I cleaned everything and still could not stop the fuel gauge from bouncing when I used the right turn signal. Adding an additional wire solved the problem.

Also, add a ground wire to the 2 gauge connections (fuel and temp) on the back of your dash pod.

 

 

 

Oh this looks good. Thx!

 

[Mike Self]

One more thing....remove the sender unit from the tank (best done when the tank is nearly empty)--lots of FAQ posts on how to do this without spilling gas all over the place.  Then carefully remove the outer aluminum housing (again, check the FAQ for a how-to), and you'll see the float that's allowed to ride up and down two hair thin wires. 

 

The wires are resistance wires, and the float connects 'em so as to vary the resistance, which the dash gauge translates to fuel level.  Take a cotton ball and soak it in carb cleaner and VERY, VERY carefully clean those wires.  Gunk will build up on 'em--especially one that sat for awhile and will affect (increase) the resistance and thus lower the gauges' true reading.  While you're at it, make sure the filter screen in the bottom of the aluminum tube is nice and clean.

 

Finally, a 2002 gas tank is very flat on top, and even when you think you filled it (the pump shuts off), you probably haven't.  If I burp my tank by bouncing the car a couple of times, I usually get at least another half gallon in the tank.  With the tank really full, the needle should be slightly above the full line on the gauge.  

 

Hope that helps

mike

[John76]

Since you just filled your tank, removing the sender can be a sloppy job.

Use a meter to measure the resistance between the insulated tab on the sender a solid ground.

If the reading is close to 3 ohms, the sender is good. Full tank = approx. 3 ohms.  Empty tank = approx. 80 ohms.

If all is good with the sender, then concentrate on checking your ground wire(s).

 

[DuctTape]

Thx all.