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Discussion Starter #1
My 2004 FX35 fuel pump only reads to the halfway point when filled. I replaced the passenger side fuel pump thinking it was a sensor issue but I still have the same issue. I'm not sure if the driver-side fuel sensor is the problem or something else altogether. The fuel gauge does move toward empty but never pass mid point.

Any help would be appreciated.
 

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from my understanding there are two sensors, one on either side of the drive shaft. I've had my passenger actually jam on the bottom of the tank periodically which makes my tank read as empty. so by that logic the driver's side float is the one that measures the "top half" of the tank so it stands to reason that if yours is jammed or dead your gauge would read as half full.

Unjamming mine was simple, I just lifted the float assembly half an inch (didn't even need to disconnect hoses/cables) and wiggled it around a bit, then reconnected
 

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Discussion Starter #3
Yesterday, I removed the driver-side pump and replaced the sensor gauge using that came with old passenger side to see if any difference was noted. There was some small amount of gas inside the driver's side tank. The gas gauge itself was reading near empty but it had to be half-full given that the other passenger tank holds the main suction pump hat drives the engine. Noting change.

I then replaced the sensor gauge back and flipped the paddle 180 degrees inside the tank, nothing change. If the passenger side is still holding half a tank of gas, I would assume that the new pump I installed a couple of days back would show half a tank, but it shows near empty. Only when I fill the tank up will it raise to half fill. Basically, working completely opposite to the logic you mentioned.

When filled = gauge reads 1/2 full
As it drains, the gauge drops to empty, yet it still has gas in the driverside tank. (This happens even with the new pump).
From then on, I need to watch my mileage or run out of gas.

I'm now thinking of a bad gas gauge on the dash. I would hate to hassle with that.

Thank you for your input. I will double-check the passenger side paddle and see if it gets stuck with the underlying feeder hose to the pump or anything else inside.
 

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Discussion Starter #4
I'm now sure that the fuel pumps are not the issue. I now suspect the issue is in the passenger side electrical sender unit that transmits to the dash panel gauge. I would be interested in knowing what readings I should be getting out of the pump from the 4 pin plug in the main pump. Any help would be appreciated.
 

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try this page, I think this is where I'd got information from (I'm sure the info is similar for most FM platform vehicles

 

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Discussion Starter #6
I will try this tomorrow. Today, I removed the passenger fuel pump and tested the resistance off of the leads coming from the sensor to the soldered point that connects to the male plug on top. It read 3.5 to 80 ohms in its swing. I did not think to test it off the head of the male plug pins.

As a note, this is a new fuel pump unit and it shows the same issue as the replaced unit. This leads me to believe that it's not the pump. Still. I'll check it again from the plug end. Thanks.
 
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