I ended up rebuilding an Auto Cocker today. I’d aired it up in the morning and thought that the cocking force was a bit light on. The back block was a bit too spongy when pushing back against the ram. So I tweaked the low pressure regulator (LPR) and all hell broke loose. The LPR suddenly delivered full pressure to the cocking system causing the 4 way’s o-rings to fail and the hoses to blow off with a sharp crack. Hmm that was embarrassing.
So I stripped down the LPR and the 4 way and discovered that the urethane o-rings were completely perished. They were so crumbly that I was surprised that they had held together this long.
The other thing that surprised me was how much grunge was inside the LPR and 4 way. They both needed a good clean. I also stripped down the high pressure regulator (HPR) for good measure and replaced its main o-ring whilst I was at it.
Whilst I had the marker apart I cleaned and lubed the hammer and checked the sear release. Unfortunately I couldn’t get the sear screw out so I had to clean it in situ. It looks like the locking screw had been overtightened damaging the sear screw’s thread. But that’s a job for another day.
Everything went back together without an issue and I only had to tweak the timing a tiny amount to stop a leak from the 4 way. I don’t think it’s been apart for around twenty years so I can’t complain really.