Fuel Sender/Gauge

[Oren09]

My fuel gauge stops working at 1/2. Meaning it never goes below 1/2, just stays there. The car has run out of gas at 1/2 a few times...
I pulled the pump module out of the tank to test/inspect it. Everything is intact and I cleaned the contacts. The sending unit works perfect out of the tank. It reads empty, 1/2, and full as it should. There's nothing in the tank that could obstruct the float.

Why will it not read below 1/2 when submerged...?

[JohnGunn]

Just to be sure I understand how you tested the sender and gauge. With the sender out of the tank and still connected to the gauge, with ignition switch on, you moved the float up and down and saw the appropriate corresponding movement of the gauge. Correct?

If so, there must be some restriction to the movement of the float arm when it is inside the tank. I assume you noticed no such restriction while it was outside.

Here is one difference between the action on the float arm when inside the tank as opposed to being outside when you tested it. As the float drops slowly is spends a lot of time at each position along the way. At each point, as the car moves the fuel moves around pushing and pulling the float and the arm into many different positions. If there was a slight irregularity in the piviot point of the float arm at the 1/2 full level this movement of the fuel might allow the arm to get caught in that irregularity and remain stuck there.

You could test this by concentrating on the movement at and close to the 1/2 full gauge point. As you move the arm slightly up down and sideways through that point see if you discover a point at which it sticks. You might even want to turn the pump upside down and move it to see if any irregularity shows up. I know this is a stretch so take it for what it may be worth.

John Gunn
Coronado, CA

[Oren09]

I tested it how you stated in your top paragraph.
I'll pull it out again and check in the tank again and closely examine the arm movement.
Probably won't get to that today, though.