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Hi::
This "stalling engine on takeoff," is , and
has been a problem with gravity feed engines.
the true problem is the fuel line in it's routing
from the tank through the gascolator droops below the needle valve input to the
carburetor somewhere, and an air bubble exists in this location.
To illustrate, place a couple of hundred pounds of
sandbags on the tail of a coupe and weight down the tail which will allow you to
observe closely the true angle of the hoses, and tubing fueling the engine, by
looking closely, you will probably be aware of the "Low spot" almost
immediately. with the tail down have someone blow air into the header tank
to keep "head pressure" on the fuel, and bleed off the fuel line where it enters
the carburetor. you will probably see a little air pass through.
Lower the plane and refuel. The bubble won't redevelop if you don't run
the header tank out of fuel, or drain the fuel line to the
carburetor.
This problem usually occurs when lines are
repositioned under the cowl, or someone replaces an aluminum or rubber line with
one that is a little too long.
Wayne Woollard
----- Original Message -----From: Charlie RenoSent: Sunday, September 07, 2003 6:26 PMSubject: Re: [COUPERS-TECH] Engine Power loss----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----I had a similar problem of losing partial power when I rotated to lift off.After several hours of AP time/testing, the main cutoff fuel valve was replaced.I have the original(in perfect condition) in front of me and just used a screwdriver to repeat some tests.The handle comes off with removal of a single screw. the hex shaft allows the handle to be put back on 60 or 120 degrees out of phase. Putting the handle on correctly: shut off and no air can be blown through. Both 60 and 120 out of sync reinstallation make it behave such there is still much air easily blown when in the "off" position OR IN THE ON POSITION. However, the amount of fuel flow is reduced below normal in the "full on" position.I had had to replace my handle several times as it came off in flight!After lift off rotation, there is a bit less "head" between tank and carb! Hence reduced fuel flow and reduced power(RPM).I came back to the field(5300 ft long) and landed down wind by declaring emergency. This was after a cylinder replacement at annual inspection time at local FBO! Then the expense and replacement of valve.Experiment: Run engine at idle, turn main valve full OFF and see if engine still runs. If so, review the history of rotated handle.Charlieps I keep the original valve as a reminder of having learned something!----- Original Message -----From: John SteelSent: Sunday, September 07, 2003 3:48 AMSubject: [COUPERS-TECH] Engine Power loss----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----Group,
I have been having a problem recently, and I thought I would get some input from the group. my 1946 415 C/D with C85 and Marvel Carb will loose some engine power shortly after take off, the RPM's will decrease to about 1900 RPM, this does not show up on the ground in the mag check or even in a full static run up on the ground.
when it happens you can turn off the left mag, and then the right mag in the air and there is NO EFFECT. Full carb heat does not help either.
So far I have cleaned the plugs, then replaced the plugs with new ones, Checked for water in the fuel, and there is no water in the fuel.
Strange that this does not show up on the ground. I am getting pretty good at getting it back to the runway, But would rat6her practice this knowing that I have full power if I need it.
Any Ideas ??
John Steel
94115
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