I have had a Wren MW44 in an L-39 but have been unable to start it due to overtemp condition on each try. I finally took it out and put it on a test stand and it started and ran perfectly each time. I think my problem is either the fuel system or temperture probe. The instructions say the probe should extend 4mm into the tail cone. It was set at 4mm while the engine was in the plane. When I put it on the board I extended it only 2mm. Is 4mm correct? The instruction manual I have was for a two piece cone. This engine is an autostart version with a one piece cone.

Thanks for any help.

Hal

Try it at 4mm on the test stand and if it doesn't start you know that was the problem and not the fuel system.
Call Sarah at Wren.

try turning your gass down, you only need to reach 100 + degrees c before the fuel pump is switched on

Hal,

The problem may well be that the engine is mounted too close to the jetpipe. The original jetpipe instructions show a 10mm gap, but this is a minimum and it will work fine with 20-30mm between the end of the exhaust and the bellmouth of the jetpipe.

If you have further problems, please email Wren directly, or phone and talk to one of the guys here.

Sara Parish
Wren Turbines Ltd