REFLECTOR: Franklin

[Hiroo Umeno]

Last weekend, I went to the hangar with my wife.  We pulled the cowl off, pulled the plug and went to work on them.  While there was no sign of deposit evident on them, some of them (particularly bottoms of No. 5 and No. 6) were soaked with oil.  We soaked all of them in lacquer thinned, then took stainless-steel brushes to clean off any deposit that might have formed.  After drying them all out, we put graphite lube on the threads and installed them to 360inch/lb torque.  While the cowl still off, I tried starting it again.

This time, it will not start AT ALL.  I tried about 6 times, each time cranking for about 10 - 15 seconds each.  Heeding you'all's advise, I did not pump the throttle while not cranking and I tried one and two strokes of throttle movement on two occasions.  I tried booster ON and OFF, Mixture rich and leaned.  After each attempt, I let the engine sit for a minute or so so as not to build up unburnt fuel in the system.

I suspected flooding or otherwise over-fueling, so after some of the attempts, I got out and sniffed around the exhaust for AVGAS smell.  To my surprize, I did not smell much at all.  Admittedly, it was a bit of a windy day but I was standing downwind and I would have smelled fuel.

I should note that I got it to make the "Brr" noise once indicating there was some ignition but it did not catch.

My fuel system is a fairly standard FG setup with sump and electrical boost pump.  I have the Franklin fuel pump AD done with a bypass with a check valve.  I do not have the primer yet (parts are on order).

The sump pickup is on the bottom as factory specifies and the fuel line run "uphill" for a bit to about halfway between the carry-through spar and fuselage bottom where the boost pump, flow sensor and fuel filter is located.  From there, the line goes through the firewall, to a T-fitting that separates the bypass line and the feed to the mechanical pump.  After the pumpl, it will re-merge and drop down to the Carb. The fuel pressure sensor is located at the Carb.

When I turn on the boost pump prior to cranking, the fuel flow and pressure both indicate activity indicating that fuel is flowing.

I am really scratching my head as to what may be causing this difficulty and how I could debug the problem.  With the electrical system, I can go around poing each connections with a multimeter and what not but I am at a loss as to what to do with the power plant.

Somehow, I am suspecting that the fuel is not getting to the carb, based on the absense of fuel smell in the exhaust stack after unsuccessful tries.  Is that a fair assumption?

One thought that did occur this week was to run the electric boost pump until I see fuel pressure and continue running until I see the flow drop to near 0 indicating that the bowl on the Carb is full and the float has tipped the fuel supply off.  Perhaps the fuel line is filled with air while the aircraft sits on the ground.

Is this a sound reasoning?

Hiroo



________________________________
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Laurence Coen
Sent: Tuesday, September 05, 2006 8:47 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Franklin

Hiroo,

Here's how I did it.  I made my primer injectors form two AN822-2D elbows that are screwed into the bottom center primer port on each manifold.  The original Franklin primer manifold injects fuel at three points in each manifold. The threads on the manifold plug are straight and not pipe.  You can convert them to pipe by running a pipe tap in a few turns because the thread pitch and diameter are a match.  I made a spray nozzle by tapping the inside of the AN822-2D for a short brass screw and drilling it lengthwise with a #60 drill.  I used #2 Permatex on the threads so it couldn't vibrate loose.  You need to tee into your fuel system on the pressure side of your electric fuel pump.  This goes to a solenoid valve which is in turn plumbed to the injectors.  You will need wire and a push button switch to operate the solenoid valve.