New with equipment issues

Hello all,

Sorry for what will be a long winded post- but I am unsure of what my issue may be, I'm thinking/hoping the pump. I am in Arizona and have been in our house for about a year. The house was built in the early 80's with an in-ground pool. The pool has 1 suction port, about 3 feet below the deck. Above the port, I have a debris basket that sits below a device attached to it which allows simultaneous surface skimming and floor vacuuming. We have a sand filter and the filter & pump is approximately 10' from the pool and 6" above the pool deck. I would estimate the pump sits 5' above the pump supply underground piping. I do not know how old the filter and pump are- but the pump looks be old, possibly original to the pool installation with the house.

Lately my pool pump/filter hasn't been running well at all- at start up I get no suction from the port and consequently no water return to the pool from the filter. My first thought would be the pump is drawing air from someplace. I tried checking for air leaks in the exposed piping at the pump and filter via a spray bottle with soapy water. I didn't see any bubbles formed which led me to believe no air leaks which could be easily repaired. Also, when we bought the house I had someone check the pool and the found a very small air leak in the underground pipe taking water from the pool to the pump about halfway between the pool and pump and repaired that. So to try and brainstorm possible causes, I tired the following in this order:

1.) Checked in-ground piping by placing the hose in the suction port at the pool and opening the pump debris basket cover. With the system off, no water came into the pump debris basket area (not surprising as the garden hose doesn't hold great pressure as the water would have to travel uphill).
2.) Checked the in-ground piping in reverse by placing the hose to the inlet pipe at the pump and with the aid of gravity, the water will come out at the pool suction inlet. Again with the system off.
The first two led me to believe there is not a drastic puncture in the underground pipe
3.) Removed the cover of the filter basket at the pump and placed the garden hose directly into the suction inlet of the pump. When I did this the system would recirculate the water leaving the hose, without much pressure. I expected this since the pump would be drawing air with the water form the hose as the cover was removed. The system would recirculate the water at the same pressure with the filter selection lever set to "filter" and bypassing the filter by setting the filter lever to "recirculate".
4.) If I replace the pump cover and run the pump it will not prime within 10 minutes. I turned the pump off after that so it wouldn't run dry. I can eventually prime the pump by placing the hose at the suction/inlet port of the pool- supplying the underground pipe with a constant flow of water. After a while, the pump will prime I get decent suction and the recirculation aerator to the pump will throw water.
5.) Once I have the pump primed by the process above it will run with decent suction for about 45 seconds or less, the suction then dissipates and there is a trickle at the aerator. Then after a couple of minutes the system will again repeat the cycle of 45 seconds good, 2 minutes bad. This happens if the filter selection is set to filter, backwash or rinse. If the filter is set to recirculate, this cycle dynamics will change slightly- maybe a full minute to 1 min 30 seconds of prime then nothing and repeat.

Therefore, my hypothesis is hopefully the pump is just 'going bad'. This very unprofessional opinion would be in tandem with:
1.) Once the pump is "primed" it loses its suction quicker with the filter set to anything but recirculate since the horsepower needed from the pump would be less due to not needing to cycle the filter ie: water level dropping and rising. and,
2.) The pump prime/suction works then doesn't work on a repeating cycle- I would find it very hard to believe that any air gaps would be variable- either their is an air gap or there isn't. Nothing that I know of is creating a variable air gap.

I have some very limited knowledge of pumps, but I have never heard of them diminishing their effectiveness over time. From what I have seen either the work, or they don't. No in between.

I am trying to schedule someone to come out this week to inspect the system. in the meantime, any help/advice/thoughts would be GREATLY appreciated if only to hopefully put my mind at rest. A $500 pump is manageable for us. A more expensive filter or having to dig up the pipe and/or drain the pool and replace piping would be really crappy in comparison. Sorry again for the long winded post! Thanks!