Off the truck topic a bit, but this newsgroup has the best techs.
Guys like "George", (ww2 Pacific Air Theatre)
All kidding aside.
This problem is a 2.4 liter GMC twin cam engine with the TIMING GEAR DRIVEN WATER PUMP.
How do you get the timing chain tensioner (hydraulic + spring) to re-tension (bounce bask out) after reassembling the timing chain after a water pump replacement? Yup, pinned the timing gear alignment holes to reset chain timing. The chain tensioner pushed in easily with some spring tension, seemed to lock in when turned and now won't release or bounce out, even under hydraulic pressure after test startup.
Spud