1968 2000 TC Restoration Project

I installed the alternate fuel tank sending unit as described earlier in this thread. The hope was to get improved accuracy. I hit a stumbling block when I tried to attach the fuel lines. This reproduction unit has the two fuel connections too close together to attach the original OEM fuel lines. I made a small modification with to the way the lines attached and was able to get everything connected. Not what I would have preferred but it should work. I have the 55 litre tank. The good news is that I added 6 litres of fuel (the reserve amount) and the gauge still read as empty. I added another 20 litres and the gauge read just under half full. Hopefully it will read full the next time I go to a filling station and top the tank off. So far, this is much better accuracy than the old sender.
 
I filled up the fuel tank today and unfortunately the gauge only reads 3/4 full. It looks like I still have more work to do. Given the measurements of resistance I made with the 2 differemtnt senders, I would not expect this problem at the top end from an electrical issue. I am wondering if the orientation of the sender is off enough that the float is contacting the side of the tank as it gets close to the top of the tank. Time to drain the tank again and check out my new theory.
 
Didn't you check the sender out of the tank but connected to the gauge to verify if the float movement corresponds to the correct indications?
 
Demetris said:
Didn't you check the sender out of the tank but connected to the gauge to verify if the float movement corresponds to the correct indications?
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As you state, I did check that things worked with the unit out of the tank and connected to the gauge. That is why I am leaning towards the idea that it is a mechanical issue. I measured inside the tank with the sender removed and there was 12 inches of vertical room. I bent the float arm slightly to achieve 12 inches of extension at full travel of the rheostat. It is possible that I installed the float into the arm 180 degrees in the wrong position and it could be running into the side of the tank. There is a tab on the sender that locks into the tank to keep the sender in the correct orientation but it is fairly "sloppy" and there is some latitude to move the sender back and forth. Tightening the lock ring could push the sender hard against one side of the tab and create an issue. Only draining the fuel and taking it apart again will solve the mystery.
 
The fuel tank sender is now working properly. The float was making contact with the side of the tank as it reached higher levels. I rotated the float 180 degrees so that it is pointing away from the base of the sender unit and now it clears the side of the tank. This sender seems to be quite accurate. Unfortunately due to the other issues with its construction, they are no longer available.
 
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