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Date: Tue, 07 Sep 2010 10:48:36 -0400
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From: Tom Thibault <tthibaultsprint@earthlink.net>
Reply-To: Tom Thibault <tthibaultsprint@earthlink.net>
Subject: RE: Dukes fuel pump problem
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Russell,

Some questions first.  Are you saying that the pump did not turn (no noise =
at all) or that it would not develop pressure but did make noise?  Be sure =
the cockpit is quiet and your headset is off your head.  You should be able=
 to hear the pump.  When it is pushing fuel it sounds a little labored.  Th=
at is good.  When it is dry, it spins faster.  This is bad.

If no noise at all,  does anyone know if there is a thermal overload circui=
t in the Dukes pump?  Does it reset itself when cooler?  If true, then you =
are probably OK, Russell.

If no pressure, this just sounds like vapor lock.  The high heat evaporates=
 the fuel at the pump and it can not push the air bubble.  Be careful to ru=
n it only a few seconds at a time in this condition.  The pump can not be r=
un dry for long, it overheats and will destroy itself quickly.

In general with the vapor lock, you just have to use a good hot start proce=
dure.  This varies from Lyc to Continental, you did not say what you have. =
 This works for me in an LNC2 with Lyc IO-360.  When heat soaked, more than=
 15 minutes:

1.  Mixture off.

2.  Throttle about 1/4".

3.  Engage starter.

4.  At first fire, full mixture and Dukes fuel pump as required.  The engin=
e will be very rough until all the air is purged.  Fuel pump off as soon as=
 the mechanical pump can keep the pressure in the teens or better.  If the =
engine does not start on that first try, the likelihood of another try righ=
t then is very low.  You got a burp of running from vaporized fuel down str=
eam from the servo, and once it is gone it will be difficult to pump more u=
ntil the engine cools off.=20


If you can do a very fast re-fuel or pax swap (shut down for just a couple =
minutes), then:

1.  Mixture full.

2.  Throttle about 1/4".

3.  Dukes pump for about 1/4 to 1/3 of the time you would use for a cold st=
art.

4.  Engage starter.

5.  At first fire, full mixture and probably much less with the Dukes pump.

Good Luck,

Tom


Russel wrote:

"Yesterday after flying into a field the Dukes of electric fuel pump would =
not run at all. I was forced to leave the aircraft at the field because I c=
ouldn't get the engine started.=20

The field elevation was 1300 feet and it was close to 90=C2=B0. The density=
 altitude was about 3000 feet for the day."


=20