Same song, third verse: work a small break in the Proseal to remove the fuel sender plate and ground plate to gain access into the bowels of the tank.
Below is the original return line that is being removed. A total of two rivets that held clips which restrained the line to the roof of the tank were drilled out, the AN fitting loosened and the assembly removed. Relatively easy process requiring no more that about 20 minutes.
In order to minimize or eliminate any outlet flow disturbances in the sump or baffled section of the fuel tank, the flow of the returning fuel needs to be slowed down as much as possible. To that end, I substituted a larger 3/8 inch AN fitting and upsized the new return line to 3/8 from 1/4 inch. Shown below are the 1/4 inch fitting on the left and the new 3/8 fitting on the right.
Next, it was time to get creative and bend some tubing into the new shape required to bring the returning fuel back to the bottom of the sump area of the tank and as far away from the outlet drain as possible. Furthermore I also attempted to have the outlet of the return line close to one of the baffle walls, again, to minimize any risk of disrupting or disturbing the outlet flow of fuel. The resultant line is shown below.
Yet another attempt to slow the flow rate of the returning fuel was to drill 5 more #30 holes in the sides and bottom of the return line to more evenly and gradually disperse the returning fuel into the tank. The next two pictures attempt to show the auxiliary holes.
Break out the Locktite 567 thread sealer and wrench down the new return line. It was quite a challenge to photograph the installation with one hand reaching the camera blindly into the fuel sender plate's hole and capture the image I was after. Shot below shows a portion of the line's AN fitting and the tubing turning over and approaching the opposing baffle wall.
Yet another couple of poor quality shots of the new return line installation with and without the camera flash.
The last two pictures of the installation that give a bit better perspective of what I was trying to accomplish with the alternative location of the return line.
As I was beginning to put the tank back together, I took the opportunity to double-check the published spec's of the sender unit. Van's states that the fuel sender's minimum resistance "should be approximately 30 ohms. The maximum resistance should be approximately 240 ohms."
Fate pitied me for all of my fuel tank sorrows and smiled upon me. As I tested the unit again, I found that the max resistance would never go past 198 ohms, but the other stop reached exactly 30 ohms. Further investigation found that the last 3/16 inch of movement of the float arm resulted in a dead spot on the unit. I never could get a full scale reading past the 198 ohms. Thankfully, I had saved the Stewart Warner box, found the part number and went shopping on Ebay. 30-something bucks later I'm in business with a new unit on order. I removed the old unit from the ground plate, cleaned it and the sender plate up and all is ready for the wicked Proseal yet again.
And yes, I will be testing the new unit for full resistive range before I install it. So, this was my "blessing in disguise."
One final thought. The Van's Pilot Operating Handbook, states in the Before Takeoff section on page iii, "Fuel Quantity Indication - CHECK (no take-off with less than 4 gallons fuel)."
....Fast forward a few days.....turns out my blessing in disguise was just an extraordinarily stupid mistake on my part. When one checks resistance with an Ohm meter, one must use the proper scale. Its pretty fundamental that when using a 200 scale setting on the meter and the measured entity exceeds 200 ohms, that the meter would stops displaying values! Such ends the saga of the bad fuel sender. Oh well, at least I now have a back up unit. Also, it was quite satisfying to find that the tech people at the distributor from whom I purchased the sender unit reproduced my "error". To their credit, they figured out the problem in about 15 minutes.
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