HP Laserjet 6l trouble

[xmastree]

Any experts here? My 6l is becoming unreliable.

What happens it that it will start feeding, then stop after about 1 1/2" of paper has fed in. The wheels are still turning at this point, and sometimes it will pick up the paper again and continue feeding. If this happens, it will stop again as (presumably) the sensor at the end of the run expects to see the paper, but doesn't since it's a little bit behind where it ought to be.
So, it stops with a jam.

Other times, when the paper stops after the first 1.5" it stays like that, then it all stops and I have to reset again.

I've taken it apart as much as I dare (and had time for) cleaned what I could, especially the two optical sensors (but not the 'exit' one) but it still fails.

If I feed some card in , and push it, I can feel it stop and start again, even though the wheels don't stop. It's as it it's hitting something.

It's hard to see what, with the toner in place, but without it there's nothing to see. As if it's hitting the cartridge itself.

Sorry if this doesn't make sense, I've been at the thing all evening and I'm too tired now so I gave up for the night...

FWIW, It's had the separation pad thing done, some time ago.

 

[xmastree]

So, having slept on it, I had another go this morning. I found out why it stops pulling after 1.5", then picks up again.
There are two rubber wheels, and two nylon pinch rollers. The rubber wheels are worn so they aren't pushing on the rollers so hard, and they're no longer round, so they grip at the wider part but not at the narrow part.

So, I bodged it for now, while I look for some spare parts.

The yellow arrow shows part of one of the rollers, and the red is my 'adjustment'. Two bits from a drive bay cover jammed in above the holders for the rollers, thus pushing them down harder on to the rubber wheels. You can't see the rubber wheels, they're below that curved panel.