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From: Berni <bbreen@cableone.net>
Subject: Re: [LML] Re: Fuel restriction or air?

Scott:

I just read your response and I believe you may have nailed my problem.  At t=
he very least you have given me a good procedure to check what I believe to b=
e the culprit...air leaking into the fuel system via the fuel selector valve=
.

I will let you know how I make out.

Thank you!

Sent from my iPad
Berni Breen
Bbreen@cableone.net

On May 15, 2011, at 7:48 PM, Scott E Keighan <scottekeighan@sympatico.ca> wr=
ote:

> I had the exact same issue 2 years ago.  It took me 6 weeks to finally tra=
ck down the problem.
> I did the same things as yourself as in dismantaling the engine driven fue=
l pump, took the entire fuel system apart from the engine
> pump to the injectors, checked all the fittings and connectors from the ta=
nks to the engine etc.
> =20
> An auto mechanic told me how to find the problem,  vacuum not pressure.  L=
ots of time a system will hold pressure but not
> a vacuum.=20
> =20
> My issue was a broken o-ring on the fitting for the electric fuel pump (go=
t old and brittle).  Air was being sucked into the
> system via the broken o-ring.  This is what you do to check for this.  Go t=
o Harbor freight and get a
> hand pump vacuum pump (around $29).  Remove the fuel line at the engine fu=
el pump and make
> a fitting that will work with the vacuum pump.  Place your fuel valve to t=
he off position.  Try to get some
> of the fuel out of the line by the vacuum pump as the fuel will ruin the d=
iaphram at the pump (i learned this
> the hard way).  The pump will hold a vacuum if everything is ok.  If there=
 is a leak start to disconnect fittings
> and cap them off between the fuel selector valve and the pump to determine=
 where the leak is.
> =20
> Another check is to run the electric fuel pump with the mixture at idle cu=
t off. Have enough fuel in the tanks to cover the
> fuel return ports in the tanks.  If you hear bubbles in the tank then air i=
s getting induced into the system. (mine did this also).
> =20
> Good luck
> Scott Keighan
> LIV=20
> =20
> =20
> =20
>=20
> =20
> > To: lml@lancaironline.net
> > Date: Sun, 15 May 2011 08:04:47 -0400
> > From: bbreen@cableone.net
> > Subject: [LML] Fuel restriction or air?
> >=20
> > I have been trying to chase down the cause of a fuel issue in my normall=
y aspirated Lancair IV engine. During a cross country flight my fuel flow in=
dicator began to show fluctuations which I mistakenly believed to be false r=
eadings. Shortly thereafter during the same flight the engine began surging,=
 slightly at first but increasingly worse in short time. So much so that I b=
egan to plan for an emergency landing as I was looking to find the cause and=
 to introduce a remedy. I turned on my electric (back up) fuel pump and the e=
ngine immediately began to run strong and the fluctuation readings stabilize=
d.=20
> >=20
> > After gaining altitude I turned off the electric pump and the unstable f=
uel flow readings as well as the engine surge returned.
> >=20
> > My initial take was that my problem was caused by a failing engine drive=
n fuel pump. Even with that belief (once back on the ground) I checked as mu=
ch of the fuel system as possible looking for potential restrictions. I look=
ed at and cleaned the screens at the wing root connections as well as the in=
let on the GAMI injectors. I found no restrictions so I removed and exchange=
d my engine driven pump for a rebuilt unit.
> >=20
> > After installing the rebuilt pump the engine tested fine on the ground a=
nd fine in the air on a subsequent cross country trip. Approximately 2.1 hou=
rs of flying time later the exact same symptoms returned...erratic fuel flow=
 readings followed closely by engine surge.
> >=20
> > I am now at a loss as to what I should now look for. Could my problem be=
 due to air somehow being introduced into my fuel flow? Should I be looking a=
t my fuel selector as a possible culprit? If so how would I test that possib=
ility?
> >=20
> > Any and all suggestions would be most appreciated.
> >=20
> > Sent from my iPad
> > Berni Breen
> > Bbreen@cableone.net
> > --
> > For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.h=
tml