flyrotary@lancaironline.net Mailing List Archive

Kelly,

This was not done to work around leaky injectors (I have six new injectors) but to ensure that if I ever run a tank dry that the pump could re-prime itself. While doing ground testing I discovered that if I ran the fuel tank dry the EFI pump could not re-prime itself, resulting in a vapor-lock situation. The only way to get it pressurized again was to crack open the fitting near the fuel rail while running the pump and bleed off the air which would get the pump sucking fuel again. There was at least one incident involving an Eggenfellner a/c that had this problem which resulted in a forced landing. They came up with the "bleeder circuit" as a fix. I borrowed the idea from them. It is discussed on their web site. I've tested it and it works like a charm. I don't recall the exact size fitting I used. It was an old 2-stroke motorcycle jet that I had in my toolbox. Any small jet should work. Bobby Hughes also incorporated this design feature into his RV-10. I recommend it to everyone, or else don't run your tanks dry.

The only thing that I can think of that would make this unnecessary is if this happens in flight your engine will probably continue to windmill which should keep the injectors cycling. This could allow enough air to pass through the system to eventually allow for a re-start. (This didn't happen with the Eggenfellner installation.) If this happens at low altitude you may not have enough time for the engine to re-start though. Personally, I feel this is such a simple fix, I didn't see any reason not to do it.

Mark

On Sat, Jul 2, 2011 at 8:52 AM, Kelly Troyer <keltro@att.net> wrote:

Ernest,

Your EFI fuel pumps have a check valve in them and will hold regulated pressure

for a long time or until leaky injectors relieve this pressure..........Short of replacing

the injectors the fix is to put a pressure relief orifice from the fuel pressure line to

the fuel return line......This is the band-aid fix commonly used for hi-milage RX7's

and "Mazdatrix" even sells a kit for this (I made my own for my 88 Rx7).............The

orifice needs to be small (I think I used 0.020).............The fuel pump has enough

excess capacity to make up for the small amount of leakage when the engine is

running...........Make the orifice very small...........I bought a kit of micro sized bits

from "Harbor Freight Aircraft Supply"........<:)...........Mark Steitle did this for leaky

injectors on his 20B..........Jump in here Mark.........Do you recall what orifice size

you used ??..............

Kelly Troyer
"DYKE DELTA JD2" (Eventually)

"13B ROTARY"_ Engine
"RWS"_RD1C/EC2/EM2
"MISTRAL"_Backplate/Oil Manifold

"TURBONETICS"_TO4E50 Turbo

From: Ernest Christley <echristley@nc.rr.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Friday, July 1, 2011 11:23 PM
Subject: [FlyRotary] Leaking injectors?

I was installing a coolant overflow bottle today, working right next to the intake manifold. Kept smelling gas. Then I noticed a little puddle inside the little depression formed by a modification I just added. The new fiberglass didn't have any paint on it, so that is why I could see through it. There was maybe an ounce of gas floating around in the bottom of the manifold.

Could I have been running so rich during my test run that an oz of gas was left on the manifold walls? Or could it be that it dripped through a leaky injector, even though I shut down by switching off the fuel pump in order to relieve line pressure?

I know some others have had problems with leaky injectors. Does anyone have an idea for making them not quite so leaky?

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