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Date: Mon, 16 May 2011 13:24:37 -0400
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Subject: Re: [LML] Re: Fuel restriction or air?
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From: Berni <bbreen@cableone.net>
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Bob:

Thanks for your thoughtful response.  I am on it and will let you know how I=
 make out.

Sent from my iPad
Berni Breen
Bbreen@cableone.net

On May 15, 2011, at 7:48 PM, Robert R Pastusek <rpastusek@htii.com> wrote:

> Berni Breen wrote:
>=20
> I have been trying to chase down the cause of a fuel issue in my normally a=
spirated Lancair IV engine.  During a cross country flight my fuel flow indi=
cator began to show fluctuations which I mistakenly believed to be false rea=
dings.  Shortly thereafter during the same flight the engine began surging, s=
lightly at first but increasingly worse in short time.  So much so that I be=
gan to plan for an emergency landing as I was looking to find the cause and t=
o 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 fue=
l flow readings as well as the engine surge returned.
>=20
> My initial take was that my problem was caused by a failing engine driven f=
uel pump.  Even with that belief (once back on the ground) I checked as much=
 of the fuel system as possible looking for potential restrictions.  I looke=
d at and cleaned the screens at the wing root connections as well as the inl=
et 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 and=
 fine in the air on a subsequent cross country trip.  Approximately 2.1 hour=
s of flying time later the exact same symptoms returned...erratic fuel flow r=
eadings followed closely by engine surge.
>=20
> I am now at a loss as to what I should now look for.  Could my problem be d=
ue 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 possi=
bility?
>=20
>=20
> Berni,
>=20
> I suggest you check two other things. First, be sure the tank(s) you are f=
eeding from are properly vented. A blockage of the vent will cause a vacuum t=
o build within the tank as you burn fuel, eventually keeping the engine-driv=
en fuel pump from being able to draw fuel. (as an aside, Don Goetz, renown L=
ancair test pilot, told me once that he'd observed the ribs showing in right=
 wing of a Lancair he was flying, and wondered that he'd never seen anything=
 like it before...the wing skin seemed to be shrinking around the ribs. Then=
 the engine quit, and the cause became obvious)=20
>=20
> Second, check for an air leak in your fuel supply system. Test this by cap=
ping the fuel lines at each wing tank and apply a slight vacuum to the engin=
e fuel pump inlet line. This little tester from Amazon is inexpensive and ve=
ry useful for this...as well as pitot/static system troubleshooting. http://=
www.amazon.com/Actron-CP7830-Hand-Vacuum-Pump/dp/B0009XQUK2/ref=3Dsr_1_1?ie=3D=
UTF8&qid=3D1294676784&sr=3D8-1 =20
>=20
> Switch tanks with the control valve to test both positions...and the conne=
cting lines. The fuel selector valve is a known issue for leaking air into t=
he fuel lines under a very slight vacuum, while testing OK under positive pr=
essure. Overhaul kits are available.=20
>=20
> Good luck, and let me know what you found.
>=20
> Bob Pastusek
>=20
> --
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