ANSWER:
If you've installed 2 new fusers and both are having jamming issues then odds are the fuser probably is not the issue. A number of things could be causing this. Some suggestions are:
1) Sensor issue
2) Slick or old pick up and separation rollers
3) Actuator is stuck or broken
4) Registration assembly (rarely it is this but once in a blue moon it is)
Posted by Jim Hawkins, 6/15/2016