With the engine not running and the fuel tank about empty, hold the plane nose up (vertical) and shake the plane. Make sure you can hear the clunk "clunking" inside the tank.

Here's how many of us tune these engines:
1. Fuel tank 1/4 full.
2. Full throttle, peak the engine by turning in the HSN to get max rpms.
3. Go back down to idle and let idle for about 1 minute (around 2500 rpm), pinch the fuel line. If it quits instantly, open the LSN 1/8 turn. If it runs for a long time and speeds up, close the LSN about 1/8 turn. Repeat until correct.
4. From idle, slam the throttle to full, if the engine quits, the LSN is too lean, open another 1/8 turn. If it hesitates and slowly gets to full throttle, LSN is too rich, close the throttle 1/8 turn. Repeat until correct.
5. Go back to full throttle, and richen the HSN until you hear a drop in speed. If you have access to a tachometer, try to get a 300-500 rpm drop from peak. (edit: you can do this adjustment while holding the plane veritically up.)
6. If this works out, you don't have to touch the LSN unless you get a very big change in temperature, or you change fuel, glow plug type, or prop size. And even then you most likely won't need to touch the LSN once set correctly.
7. If the engine still quits, then you probably have either bad fuel, wrong/bad glow plug, or a leak in your fuel system.