I installed a Perry (regulating) pump on my Skybolt/TT-120 last summer to move the tank on CG and for better fuel delivery.
It ran great last summer. The weatherman says in the 60's Sunday so I spent all morning trying to get this thing to run for more than a few seconds.

It pumps good up to half throttle but more than that it starts to pump air straight to the carb. The air is coming from the case/pressure side because there are no air leaks in the tank and no bubbles in the line up to the pump, only after it.

I thought vibes were causing this but it still does it un-mounted.

Adjusting the screw raises and lowers the pressure correctly while it's pumping solid fuel at 1/4 and lower, but when I go to 1/2 throttle the air bubbles start coming from the pump.
It pumps solid air at full throttle and dies as soon as the line runs dry.

The pump has only seen a few flights last summer, but mostly sits.
Anyone else experience this?
Do the diaphragms deteriorate this soon?
Are these things re-buildable?


Thanks for any help!!! Kirk

They are not rebuildable by the consumer.

A glow fuel one can be destroyed by using a petroleum based after run oil.

Jim

Thanks Jim.
Neither pump nor engine has seen after-run oil, WD-40, ATF mix or anything.
I only use 0-5% nitro and drain it at the end of the day. None of the fuel lines are soft and like I said, only a hand full of flights last summer then sat till now.

Could this 120 have too much crankcase pressure and blew the diaphragm?

I would assume this is how they fail?

Is there anyone out there with years of service from one of these?

Thanks, Kirk