I worked on a Toro Model 2005 with a techumseh Engine. I did a tune up on it and it runs great when it left my garage. My friend cuts the grass and after 15 minutes or so it just dies and won't run or start again.
So I asked him to try it again and when it dies to take the gas cap off and try and start it then. He did and it died like before, however it did not start with the gas cap off and with primer.
I asked him to try it again another day with the gas cap loosen but not off.
My theory is that the gas is not getting the air needed and the carb is starving for gas. I am hoping that it will work with a loosen cap and then I can either get another cap of figure something out.
Any other suggestions?

This is my first post so I am interested how people respond.
Thanks