Last week when I was at the field a new engine problem creeped up on me. When i'm tuning the plane by holding it vertically the engine has fuel for about 10 seconds and then fuel just stops running to the carb completely. What could be causing this? I changed the glow plug checked all the crankcase bolts everything seemes tight. The engine is a .40la and is about 3 years old. Could the motor just be worn out?

Did you have a hard landing? Perhaps the clunk is jammed against the front of the tank. If so, hold it nose up & shake it hard up & down.

How does the engine sound just before dying? Like it tis too lean, or like it ran out of fuel? Could be the clunk. Could be a an air leak in the adjuster or maybe a leak elsewherealong the fuel lines. Or loss of pressure from the muffler. Make sure all your lines are airtight. Maybe take the fuel system apart to make sure everything is still secure and go from there.

I doubt if the muffler is a problem, unless something is obstructing the pressure nipple -- gunk maybe?

Agree with britbrat i had the same problem.... after much messing around turned out the clunk had come forward and jammed in the front of the tank. Shake the plane can you hear the clunk rattling?

I'll try to bang the tank to see if the clunk got jammed. I don't think gunk could be in the engine because I just cleaned it with an antifreeze treatment a few weeks ago.

Hey RCforlife. One easy thing to check is to take out the airscrew and clean it off and blow out the fitting that it screws into. I had a problem a while back that sounds like the same you're having. I checked the clunk, checked the motor for leaks, and checked the fuel lines for holes and none of those fixed it untill I took out the airscrew and cleaned it off.