Van Dorn 300 RS-Help Needed

[Dave Mclean]

Have a problem with this machine it's van dorn 300.model # 300 rs 30f vv vb made 11 86.
the problem is the screw motor go's stops go's stops go's stops? its does this in manual mode and auto.we have pressure and if you increase the flow it gets quicker but still takes a long time to go back. it all started in one cycle. all the solinode have been taken apart to check them tested for pressure at different points all solinode are getting power when needed. want to try find out before i rebuild the screw motor and its still happens.