Defective fuel sender

I’m sitting here about to start typing when the girl in my life starts chuckling………?

Apparently she was looking at Quidco and saw it.

So, back to the fuel sender.  The fuel gauge for the main fuel tank has become erratic and now reads full all the time.  After a few emails with the manufacturer I’ve decided to send it to them for testing; and if necessary repair.  Of course it’s the most inaccessible of all the tank sender units.  To get at it the inspection plate below the Morse controller has to be removed.

The port and starboard sender units are mounted vertically on the rear bulkhead.  The white hose in front goes to the deck shower outlet.  The sender unit requiring removal is behind the hose.

It’s actually a simple task to remove the sender except access is so awkward.  I need to disconnect the three electrical cable ends, the air line and then the four mounting screws.  It was the latter that caused the most difficulty.  Eventually it came out.

The sender unit works on air pressure.  A small copper pipe connects to the brass inlet fitting at the right end.  A hand pump is connected to the blind fitting sticking out the side of the unit and air pumped into the copper pipe.  The other end of the copper pipe goes down into the fuel tank just short of the base.  The principle is the weight of the diesel in the tank varies the air pressure in the copper pipe which is measured by the electronics in the small black box in the sender unit.  The reader is then sent via the wiring to the digital gauge on the instrument panel.

I was having considerable difficulty pressurizing the system and I think I “blew” the sender unit by pumping too vigorously.