Cm870 starts then shuts off,starts back up with a puff off white smoke and stays runn

[JimT]

While this is outside my area of knowledge, I'd say the top of the pickup and fittings to the fuel line are probably a good place to start. Anywhere fuel could leak out is a point where air could get in. It's clear you have some sort of leak in that area so it's a good place to start.

Also, it would be prudent to check the overhead again. There's always a chance that a mistake last time could have caused the problem you currently face.