I have a similar problem with my tc18, it will be running then start to die like it's running out of diesel, sometimes it dies all the way and sometimes it stays running only to act up again later. When it dies, it starts right back up and as soon as you switch into gear from neutral it dies. Tested that switch and it testes good. I'm pretty sure it's something in the safety start circuit, but I'm lost on where to go look. The electrical diagram shows a safety start relay, but I can't find it in any online parts store? If anyone has any ideas, I sure would appreciate them. Thanks