I have developed a ticking sound too..Being that it goes away by pressing the purge button, couldn't it be as simple as bleeding the air out of the lines?

No ... It will be the lift pump... The slack is why it ticks, allow them to do it long enough and it could pip apart and the parts can fall into oil pan ... And them no run ... Bad deal, I wouldn't recommend the airtex pumps, but ya do what ya have to do ...

Well, before starting the truck today, I mashed the primer 6 or 7 times. Started, ran around town. Stopped and started the engine a few times, to go into stores. No more clicking. I did, replace the fuel filter a few weeks back and may not have purged all air out of the system. Hopefully the ticking will not come back. 150k miles, hopefully will not need to replace the lift pump soon.

Time will tell ...