Flaps

[Joan Ford]

I removed the flap valve on my M20E to replace the o rings.  Now I can't get the pump to work.  Any suggestions??

[Jim Peace]

Where does the plane live?

[Andy95W]

That is not uncommon, assuming the pump was assembled correctly and the bleed down screw is correct.  The flap pump is very difficult to get primed, and until it does it tends to just pump air.  You can’t even bleed the system until you start pumping fluid.

Worst case is you pull the pump assembly back out and pre-load the cylinder and re-install.  Once it starts pumping fluid, the process goes fairly quickly.  Usually, though, you just keep pumping the handle and slowly enough fluid gets into the cylinder that it starts pumping and you can bleed the air out of the slave cylinder at the back.

Good luck, it’s actually a very good system that tends to work really well- once you get it done.

[M20E for me]

There are some good write ups on this topic.  Google it and you should find what you need.  I had the same problem a few years ago but don’t remember exactly what I did to get it to work but I do remember finding a really good write up here.