Masticator not running until very hot.

[Benlin]

This problem is everything contrary to owning a masticator!! The Fecon FTX-140 is having a problem heating up, it has been getting worse, along with it only liking to run way up at the top of the heat scale, it has a newer main pump, near new head motors. I suspect maybe its having a hard time picking up suction, maybe a plugged screen in tank, and the hot oil pulls better?? The John Deere runs in the middle of the heat range, the drives operate after getting about 1/3 way up in the heat. The head only likes to run strong RIGHT AT THE TOP, one bar from the RED range. Any thoughts???