I have an engine with what I think is an old Perry pump. I have heard that these things go bad somehow over time and cannot be repaired. Is there any way to tell if it works without trying to run the engine? I'm just curious because it will be a few days before I can test it on the stand. Also, I assume there are no user adjustments on these things, right?

Thanks,
David

You may check the static mechanical integrity of the pump

See if you can blow through it in the forward fuel direct.

See if you cannot blow through it in the reverse direction.

When blowing through it in the forward direction, see if it doesn't leak air from the fuel chamber into the engine

The check valves can get sticky after sitting for a long time. I free mine up by squirting a little fuel into the inlet nipple using a fuel bulb. You don't need much, maybe a teaspoon full (approx ) and then connect the inlet and outlet nipples with a short loop of fuel line.
Let it soak for a while...to loosen things up...
You might need to do it a few times...
You can get an idea of the pumps function by flipping the prop and watching to see if some fuel moves through the fuel line loop from outlet back to inlet.

Check for leaks from the vent/weep hole...and you can also remove the backplate and look for any fuel comming through the 4 little pin holes.

Thanks w8ye. With a piece of tubing connected to the "IN" side I can blow air through the pump. If I cover the "OUT" fitting with my finger I cannot blow any air through it, so it doesn't seem to have an internal leak. I can also hear something clicking inside the pump which I assume is the diaphragm (or reed).

I can just barely blow air through in the reverse direction.

proptop, I will try your test, too.

David

Ok, I squited some fuel through the pump and then attached a loop of tubing. I can watch the bubbles travel around the loop when I flip the prop. I guess that means it still works?

Thanks,
David

OK...it moves fuel...that's a start [8D]
I've had 'em pump nothing but bubbles though, so.....the true test will (obviously ) be by running it.

That brass hex screw is the regulator adjustment, and it looks like it's screwed waaayyy too far in IMO. (could be just camera angle though? )
You want to have about 3/32 to 1/8" between the black plastic pump body and the screw. The further in the screw is, the more pressure...just like an Oxy/Acetylene regulator.

I've read that there could be damage to the diaphram caused by having the adj. screw in (or also out ) too far.
Maybe that's what caused one of mine to pump bubbles?

Just out of curiosity...is that a Webra?

Yes, it's an old Webra RE .61.

I set the hex screw so that the back surface of it is about 3/32" away from the plastic housing. Does this look better?

Thanks again,
David

Yeah...that oughta be better...easier to adjust the needles.
When the pump adj. screw is too far in the carb needles need to be turned way in as well and they can get REALLY touchy.

Which carb do you have?

Right now, the backplate/pump is on a "parts" engine with no carb. Now that it seems to be working I will install it on another .61 RE that has a Dynamix to test run it.

David

That's purty [8D]
I've never run a Perry pump with a Dynamix...hope it works out well for ya...the in flight adjustability feature is a nice bonus.

FWIW...if you have a problem with it running too rich in the mid range, the pump pressure adj. screw should be backed out some more...and vice-versa.

Thanks for all your help. I actually got a lot of info out of this thread.

If it isn't easy to adjust and doesn't run perfectly on the stand, I will not use the pump in a plane. So, I might end up going back to the standard backplate and a TN carb (which is pretty foolproof).

David