Hello,

I thought the flight time problem with my Evolution 36 c/l engine was solved but this is not the case.
The engine-venturi-NVA-tank-prop-fuel-glow plug combination worked well for a while ( 7+ minutes flight times instead of 3 ) but two weeks ago the new problem appeared.

Specifically, the engine started quitting with the fuel still left in the tank.

Please see the details below - perhaps somebody experienced something so weird before.

Details:

Weather: 80 Deg. 60% humidity
Fuel: stock Omega, 10% nitro, no castor added. Did not use stock Omega, 15% nitro.
Prop: 11x4 Zinger
Lines: 60' eyelet to eyelet

Results:

1. Full tank of stock Omega 10% nitro ( 4.5 fl.oz ) burned to the last drop on the ground at 9,900 RPM.
Engine running time: 11 min. 25 s (!!) - run smoothly and very consistently, no RPM fluctuation.
Engine's head temperature immediately after the prop stopped: 289 deg.F

Let it cool for 15 minutes and the compression was completely back.

2. First flight - the same fuel and launch RPM like 1.
Flight time: 7 min 17 s. Plane landed with empty tank.
Engine's head temperature immediately after the plane stopped rolling: 221 deg.F.

Let it cool for 15 minutes and the compression was completely back.

3. Second flight - the same fuel and launch RPM like 1. and 2.
Flight time: 5 min. 07 s. Plane landed with some fuel in the tank.
Engine's head temperature immediately after the plane stopped rolling: 198 deg.F.

Let it cool for 15 minutes and the compression was completely back.

4. Third Flight - the same fuel and launch RPM like 1., 2. and 3.
Flight time: 3 min. 02 s. Plane landed with more than 50%  fuel in the tank.
Engine's head temperature immediately after the plane stopped rolling: 180 deg.F.

Let it cool for 15 minutes and the compression was completely back.

The plug used: OS Max Hot (6).

When I fly more, the flight times are decreasing and the engine quits with the fuel still in the tank.
Have you ever experienced something so weird?

No dirt in the fuel lines and fuel tank ( opened the tank already ), no dirt in the fuel filter, the plug goes bright orange while powered from the glow plug starter.

Any ideas what to check next?

Thanks,
Matt

A prop with an imbalance causing fuel foaming, maybe?

Those don't have plastic backplates, do they? Might still shift & leak with heat, even if aluminum. Some say the Evo's don't like castor oil, but I'm not sure everyone agrees on that. I'd sure check all the screws and gaskets, including the glowplug. But I can't do it tonight, I've gotta get up early to go fishing in the morning!  Steve

Everybody,
Just returned from the field with good news: the problem has been fixed by replacing the glow plug.
OS Max Hot #6 plug was simply dying. I have replaced it with the brand new Evolution medium plug and got five good and very consistent flights.

The flight time ( average of five ) : ~8 minutes with 10% Nitro Omega stock fuel, no extra castor added.

Launch RPM: 9,900 - 10,100, giving excellent lines ( 60 ' eyelet to eyelet)  tension overhead with 11x4 Zinger ( one flight: 9,900 RPM) and 11x4 APC Scimitar style prop.( four flights: 10,100 RPM).

Lap times: 5.2 - 5.3.

I consider the problem solved.

How to recognize that the glow plug is dying?
What are the indicators of it in order of importance?
What are the differences in appearance of the glow element of the dying plug and the healthy plug?

Regards,
M