Kibo informs me that Chuck Harris stated
that:

[poor paper feeding]

Paper jams on HP laserjet 3/4/5 printers are almost
always caused by a good looking takeup roller that cannot
grip the paper. The symptom of that problem is 100% of the
time the paper not quite reaching the first feed roller.

Using WD40 sounds counter intuitive, but it works! It took
a great leap of faith for me to try it the first time (on the
recommendation of a friend who deals in surplus printers), but
I did, and it works perfectly.

Back when I did this for a living, I used acetone (paint thinner or nail
polish remover) on the same roller to restore the grip. Apply with a
cloth, in the same way that Chuck described.
The reason it works is that the suface of the pickup roller eventually
hardens & loses its tackiness, resulting in it slipping on the paper
instead of gripping it. Cleaning the roller with solvent removes the
hardened surface, restoring the gripping surface.
The same method works well on the separation pad, when you get the
problem of the feeder picking up multiple sheets instead of single
sheets.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------