Using check valve in YS 140DZ fuel system

Mon Aug 30 14:39:22 AKDT 2004

Hi Earl,

Are you saying in your first paragraph that the fuel head pressure and
pressure caused by thermal expansion is lower than the pressure required
forcing the check valve to open and allow fuel to flow?

Peter

Peter Pennisi
Pentagon Systems QLD Pty Ltd
P.O Box 4280
Eight Mile Plains
QLD 4113
Australia
Phone:    61+0738414234
Fax:        61+0738414264
Mobile:   0408007206
Email: pentagon.systems at bigpond.com

-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On
Behalf Of Earl Haury
Sent: Tuesday, 31 August 2004 8:22 AM
To: discussion at nsrca.org
Subject: Re: Using check valve in YS 140DZ fuel system

Peter

You're correct regarding check valve placements regarding fuel / air flow. 
The pump inlet valve will unseat with very little positive pressure, if the 
carb is even slightly open, fuel will then flow into the head via the 
injection path and flood the engine. The intent of the check valve in the 
feed line is to prevent fuel tank head pressure, thermal expansion pressure,

or fueling pressure from causing fuel to flow to the engine when it's not 
running, thereby causing flooding (eliminates the need to clamp the fuel 
line).

The pressure drop across the check valve is very low and will not generally 
impede fuel flow unless fuel draw is diminished by a worn pump. However, a 
worn pump will demonstrate other unacceptable symptoms. Notably, loading up 
at idle and leaning on vertical uplines. (Side to side movement of the upper

inlet pushrod in the pump housing is indicative of wear.)

My favorite system is to use the loop vent and an external clamp (available 
from the heli guys) on the feed line. Simple, positive, and effective.

Earl
----- Original Message ----- 
From: "Peter Pennisi" <pentagon.systems at bigpond.com>
To: <discussion at nsrca.org>
Sent: Monday, August 30, 2004 4:41 PM
Subject: RE: Using check valve in YS 140DZ fuel system

Hi Tony,

Could you please share your thoughts on check-valve placement especially on
the injector line? Earl also suggested placing one on the fuel feed line if
I understand correctly. That makes it 3 possible locations when you include
the vent line.

I didn't know that people are placing them in the injector line. I am very
interested to hear more.

Earl, what is the theory behind placing it on the feed line. I assume in all
of the cases the valve is orientated such that it goes in the direction of
either fuel or air flow, or is there something different here as well.

Sorry for all the questions, now you have me thinking.

Regards,

Peter

Peter Pennisi
Pentagon Systems QLD Pty Ltd
P.O Box 4280
Eight Mile Plains
QLD 4113
Australia
Phone: 61+0738414234
Fax: 61+0738414264
Mobile: 0408007206
Email: pentagon.systems at bigpond.com
________________________________________
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On
Behalf Of tony at radiosouthrc.com
Sent: Tuesday, 31 August 2004 5:25 AM
To: discussion at nsrca.org
Subject: Re: Using check valve in YS 140DZ fuel system

Ed:

Most of the uses of the check valve are in the injection line going to the
head. This will also prevent the line from going empty during idle
maneuvers, and giving a hesitation during throttle up, like at the bottom of
an outside loop. I have installed one earlier this year, and it did seem to
help this issue.

Tony Stillman
Radio South
3702 N. Pace Blvd.
Pensacola, FL 32505
1-800-962-7802
www.radiosouthrc.com
----- Original Message ----- 
From: Ed Deaver
To: discussion at nsrca.org
Sent: Monday, August 30, 2004 2:06 PM
Subject: Re: Using check valve in YS 140DZ fuel system

I've used the check valve in the vent line from day one without any
problems. Have never noticed any pressure buildup at all in the tank.

ed

Peter Pennisi <pentagon.systems at bigpond.com> wrote:

Some flying buddies of mine have been having a discussion about using a
check-valve in the fuel system to essentially stop fuel from dripping out of
the vent line. I have been using this system without any problems that I
know off for some time. One of the pattern flyers I fly with is very good
with engines and he doesn't think it is a very good idea to use the valve in
the DZ fuel system as the tank will always have a slight pressure build up
inside which may result in inconsistent engine runs. I don't know about his
theory but I do know that all the Japanese flyers at the recent CAOCC event
were using check valves in the fuel system.

I would be interested to hear from anyone who may have an opinion on this
subject.

Regards,

Peter

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