PilotPete
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Does anyone know from experience tearing down or rebuilding diaphragm-type mechanical fuel pumps like the Lycoming/Tempest 15473 whether there should be any relative movement between the 2 plates on the check valves?
The assy stackup of the valve is: lower plate (swaged into pump housing); rubber gasket (seal); upper plate (connected to lower plate via a center post).
There is a small spring between the plates that tends to push them apart, so I'm assuming there should be relative movement between the two plates during operation. I am thinking that the upper plate is forced down to apply even pressure against the rubber seal to close the valve, and then reverse fuel pressure pushes the upper plate away to open the valve. The spring is there to ensure the valve fails open (safe state).
The 2 valves in my pump were seized open (ie. you couldn't compress the assy against the spring). I tapped the center post with a hammer, and it freed up so that the assy now does compress and rebound, but it's still quite stiff.
The assy stackup of the valve is: lower plate (swaged into pump housing); rubber gasket (seal); upper plate (connected to lower plate via a center post).
There is a small spring between the plates that tends to push them apart, so I'm assuming there should be relative movement between the two plates during operation. I am thinking that the upper plate is forced down to apply even pressure against the rubber seal to close the valve, and then reverse fuel pressure pushes the upper plate away to open the valve. The spring is there to ensure the valve fails open (safe state).
The 2 valves in my pump were seized open (ie. you couldn't compress the assy against the spring). I tapped the center post with a hammer, and it freed up so that the assy now does compress and rebound, but it's still quite stiff.
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