The Murphy Builders Site

Posted: **Sat Feb 18, 2012 9:50 am**

Two questions from your post George:

- If the M14P is "injected" why does it have a carburator (otherwise
stated, what role does the carburator play in the M14 injection process?

- What would it take to install a vapor return system on an existing
M14P installation?

Thank you,

Ted

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
George Coy
Sent: Tuesday, December 14, 2004 10:10 AM
To: rebel-builders@dcsol.com
Subject: RE: Rebel Fuel Management

In the good OLD days we were taught the same thing, Run one tank dry and
you know how much is in the other. That worked for carburetor engines
with a float bowl that gave some warning before it quit stone cold. With
injected engines (M14P is an injected
engine) the process may not be so safe. If you get a slug of air in the
line, the pump may cavitate for a bit before it picks up again (if it
does at all). It is not good for your heart health! Injected engines
will quit just like you turned off the mag switch. If your fuel system
has a vapor return system, then things are a little better, as the fuel
pump has a place to put the air in the line besides through the injector
system. That is why I advocate a vapor return system with the M14P
engines (IO540 as well).

George Coy
President
Gesoco Industries Inc.
629 Airport Rd.
Swanton, VT 05488
TEL 802-868-5633
FAX 802-868-4465
Web Site www.gesoco.com
e-mail George@gesoco.com
Franklin County Airport (KFSO)

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Posted: **Sat Feb 18, 2012 9:53 am**

The M14P has a pressure carb. A pressure carb is essentially a mechanical
throttle body injection system. There is no float bowl or mixture control.
A vapor return system needs a line from a point after the fuel pump and
before the carburetor that goes back to the header tank or the fuel tank.
This line should have a restrictor in it. The usual way to make a restrictor
is to fill a brass flair fitting with solder and then drill a small hole
through the solder. A #40 drill would work. The idea is that there is now a
constant flow of fuel from the tank to the pump and back to the tank. This
will also help prevent any vapor lock on hot days. (particularly if you use
auto gas).
The fuel should ideally go back to the tank from which it came or there is
a possibility of overflowing one tank while flying from the other tank. A
header tank solves this problem.
Some Be23 Musketeer's had a IO-346 (2/3's of an IO-540) and a vapor return
to the left tank only. You had to be careful with fuel management. To use
the full 6 hour range you needed to fly the first hour on the left tank, the
next two hours on the right tank and the last three hours left tank in that
order. You can see the implications of a vapor return that was to the left
tank only. My first trip to Sun-N-Fun was in a Musketeer with this fuel
system. We landed with a dead prop as the fuel system unported on that last
sharp turn from base to final as the controller turned us to the parallel
runway at the last second.

George Coy
President
Gesoco Industries Inc.
629 Airport Rd.
Swanton, VT 05488
TEL 802-868-5633
FAX 802-868-4465
Web Site www.gesoco.com
e-mail George@gesoco.com
Franklin County Airport (KFSO)

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com]On Behalf Of Ted
Waltman
Sent: Tuesday, December 14, 2004 12:14 PM
To: rebel-builders@dcsol.com
Subject: Vapor Return System

Two questions from your post George:

- If the M14P is "injected" why does it have a carburator (otherwise
stated, what role does the carburator play in the M14 injection process?

- What would it take to install a vapor return system on an existing
M14P installation?

Thank you,

Ted

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
George Coy
Sent: Tuesday, December 14, 2004 10:10 AM
To: rebel-builders@dcsol.com
Subject: RE: Rebel Fuel Management

In the good OLD days we were taught the same thing, Run one tank dry and
you know how much is in the other. That worked for carburetor engines
with a float bowl that gave some warning before it quit stone cold. With
injected engines (M14P is an injected
engine) the process may not be so safe. If you get a slug of air in the
line, the pump may cavitate for a bit before it picks up again (if it
does at all). It is not good for your heart health! Injected engines
will quit just like you turned off the mag switch. If your fuel system
has a vapor return system, then things are a little better, as the fuel
pump has a place to put the air in the line besides through the injector
system. That is why I advocate a vapor return system with the M14P
engines (IO540 as well).

George Coy
President
Gesoco Industries Inc.
629 Airport Rd.
Swanton, VT 05488
TEL 802-868-5633
FAX 802-868-4465
Web Site www.gesoco.com
e-mail George@gesoco.com
Franklin County Airport (KFSO)

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