I'm trying to help out a friend diagnose an issue with his TCM FCG15-N6 LP forklift that starts, but won't stay running unless he presses and holds in the little spring-loaded button on what I'm guessing is a fuel diaphragm. (Located on left-front of engine bay)

I have a basic knowledge in automotive and small engine repair, but when it comes to LP Forklifts I need all the help I can get.

I'm not seeing a way to share pictures, but I've put the picture of the diaphragm and the spring loaded button in my profile signature.

Thanks!