REFLECTOR: Primer Nozzles

[Laurence Coen]

John,

Your new arraignment sounds like what I did.  Attaching the primer solenoid to the starter power may have unintended consequences.  Even with the aux pump off the open solenoid valve will still allow fuel to be drawn in due to the negative pressure in the manifold.  I guess I'm just a "Nervous Nellie" when it comes to making things automatic.

Larry Coen
N136LC


From: aminetech at bluefrog.com 
Sent: Saturday, August 20, 2011 7:50 AM
To: Velocity Aircraft Owners and Builders list 
Subject: REFLECTOR: Primer Nozzles


I had plain elbow fittings instead of nozzles and decided to convert to nozzles.  I'm amazed how tiny the opening is on the nozzle (# 76 drill size).  The tubing side connection is fine thread which can't be used with the coarse thread compression fittings on my tubing lines, so I made nozzles from the plain elbow fittings by inserting a piece of brass sheet metal held in place with structural adhesive and drilling a # 76 hole.  I also moved the fittings from the 1 and 2 cylinders to the middle ones.  Before installing, I connected to the fuel lines and had someone press the primer button.  I was expecting to see a spray, but it was a mostly coherent stream of greater volume than I expected from such a tiny hole.  It shot up about 6 inches which means fuel is getting right at the back side of the intake valve.  The engine fired the instant I engaged the starter.  I'm thinking of making the priming automatic by powering the primer solenoid from the starter + terminal.  The only time I don't need priming is when the engine has been off for less than 10 minutes and I think I can "turn off" the primer by simply not turning on the electric fuel pump.

John


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