It’s just a simple PM

Doing a PM service on my truck (CAT 3406E) while replacing fuel filters I did the usual ,fill them with clean fuel (through filter side) till full, water separator o-ring replaced, everything seemed to seat nicely. Went to prime and it was a little easy at first and then firmed up. Great. After 5 or so firm pumps went completely loose. Not so great. I loosened the bleed screw, got some bubbles, got fuel flowing, still loose. Checked filters again, still topped off. Took of o-ring off and placed it again in case it didn’t seat correctly. Pump still loose. Bled air again and then for a third time and now I guess that bolt has decided to retire and totally stripped its threads… It screws down, just not very tight and will just keep turning. Question is did I probably have fuel pressure and my hand pump just by chance failed? Pretty sure I should replace the bleeder before attempting to crank over, that would probably bring air into the system. Refilling the engine oil now. I had the oil filter off for the first half of this and put it on filled in between bleed attempts. Pretty sure that doesn’t matter, but I usually deal with everything oil related first.

Feel embarrassed having to ask this, but what the heck went wrong with this simple task?

Thanks in advance.

 

It’s the one that comes with the water separator. Fits over the threads on the housing.

 

I’m trying to figure out how this happened in the first place before the bleeder stripped out. I loosened and tightened back down twice and it’s stripped on the 3rd time down