From: JIMRHER@aol.com
Message-ID: <a5.1a363973.28b4614f@aol.com>
Date: Tue, 21 Aug 2001 21:13:51 EDT
Subject: Lancair IV P fuel selector valve
To: lancair.list@olsusa.com
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I just changed my 4P fuel selector to the Andair because of the following 
stories. My plane is due to fly by the end of next month (Hope, Hope) and a 
friend who just flew his 2 months ago went through several engine stoppages 
before changing to the Andair which is what the factory now sells. It cost me 
$500.00 more and I have a brand new old type for sale. 
This friend found that by purging both tank positions before take off that it 
helped the original fuel interruption problem until he flew at high altitude 
for over 1 hr. and then, even with the purge before flight, the engine 
stopped for 20 seconds (seamed like forever, he said) when switching tanks. 

His theory(and several of us agree) is that when the selector was feeding 
from one tank the Cabin Pressure was pushing air into the Unselected tank 
line inside the Selector Valve. Upon changing to the Andair the problem went 
away.
I also flew to OSH last month in another 4P that has over 570 hrs. TT and I 
discussed this fuel problem with the owner /builder. He said he never had a 
problem but he had changed out the very first selector he got with his kit in 
92/93. So as we are flying at FL220 and switching tanks after 20 gals burned, 
the engine stumbled. He said that he may need to look into that stumble.

I changed mine because I feel that fuel flow is a MUST HAVE item. 
To change form the last generation factory selector to the Andair (current 
factory selector) is Not a trivial issue. It requires some new bent lines and 
new fittings. While I was at it I moved my boost pump to the lowest position 
under the right floor foot rest and made sure the flex line from the wing to 
the fuselage is laying as low / horizontal as possible all because if you do 
get air pushed into the line, from the selector side, it could cause an 
airlock at the high point in the line TO the boost pump. Since the pump is 
Not a self priming pump, it needs fuel to pump not air. I don't know if the 
tank vent line gets pressure from the small NACA scoop on the tip but that 
and gravity would be the only way to push the air through the pump. I also 
installed 1/2 in. line from tank to selector even though this may not be a 
real necessity.

How may others have had a fuel flow interruption issue with the 4P?

Jim Hergert
L4P in paint.
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LML website:   http://www.olsusa.com/mkaye/maillist.html
LML Builders' Bookstore:   http://www.buildersbooks.com/lancair

Please send your photos and drawings to marvkaye@olsusa.com.
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