Try pulling out the GLOW PLUG element as much as possible. Make sure your starter Assembly use the new speed 500 motor. Any slipping during startup will cause a fail start.

Remember the lower the ecu GLOW PLUG (48) setting the brighter the plug glows. Try pressing the air button to get the max RPM to jump start the engine then hit the start button. Some time its best the remove the glow plug from the engine then connect the plug wires to the glow plug then try to start the engine. This give you an idea how to adjust the plug voltage