Pool pump won't prime

Hello -

Asking for some help this year after opening my pool for the past 18yrs. myself w/o a problem.

4 days we opened the pool and the pump primed right away. My wife vacuumed the pool, once stopping the pump to empty the pump and skimmer baskets. She turned the pump back and on and the pump primed again and she continued vacuuming. When she was finished I went over to the pump to shut it off and prepare to backwash when I saw that the the pump basket was struggling to keep water in it and loosing it's prime. I shut it off and prepared to backwash. I turned the pump handle to close while I opened up the backwash valve. I then turned the motor on without turning the pump handle to backwash and then quickly realized what I had done and shut off the motor, turned the pump handle to backwash and turned the motor back on. The pump would not prime. I have done the following:

1. removed the motor (AO Smith) and checked in the impeller which was clear and turning fine.
2. replaced the diffuser ring gasket (w/grease) while I had the motor off.
3. removed the pump basket assembly from the motor housing and checked the gasket which appeared ok and put back on (little grease).
4. inspected the pump basket cover gasket that was ok, greased and put back on.
5. blew pool skimmer line and outtake line to pool and both are clear.
6. checked for intake air leaks as best I could and appears there are none. I also wrapped plastic bags around various connections that did nothing. Did not see any cracks anywhere.
7. tried to manually prime pump by placing hose, with a heavy towel wrapped around it, in pool skimmer pipe to try and force water into pump basket but was unsuccessful geting any water to pump basket.

I'm leaning towards a bad impeller and diffuser. The motor sounds fine. It is sucking water out of the pool pump basket but for some reason not sucking water in from the pool via the skimmer pipe. I also have another intake pipe from the deep end of the pool to the pump that I tried to prime independently as well w/o success. I did try to find these replacement parts for my AO Smith motor and it seems to be a challenge.

Anyone have and ideas? Also if you know where I can find AO Smith motor parts?

Pump is a Sta-Rite T-200BP1 (about 5yrs. old)
Motor - AO Smith USQ1072 Type B 115/230 volts RPM 3450

THANK YOU! Jeff

OK.

1. You started with a working pump, vacuumed and ended up with non-priming pump.

2. I suppose a bad impeller/diffuser could be the problem, if some gravel or whatnot had damaged the existing parts. But failure there would weaken suction, not introduce air into the system.

3. You did a lot of checking on the pressure side of the pump -- but again, air doesn't enter there; water leaks out.

4. You could -- if it's not a massive PITA -- hook up a temp line from the pump suction into a bucket, barrel or over the deck into the pool. That would allow you to rule in/out the failure in the pump, strainer lid or pot.

5. It doesn't sound like you've ruled out cracked lines from the pool. A crack in a below water level line would have likely been leaking out, and wouldn't leak air IN, until all the surrounding water was gone. This winter was cold enough to do freeze damage unlike anything seen in 25 years.

Gotta go . . . wife got home and we have errands.

. . . membership upgraded.