I probably should have taken a better photo but the salt system, filter and ball valves actually belong to a sperate pump that just does the pool. The pump in the photo just has the blow off valve, the suction line with the check valve (which works although I have no idea why it's even there) and the suction line.
The owner says that it worked sometimes and he would have to turn on and off the pump to get it to prime. When you put a hose into the pump basket, the infinity edge trough just overflows into the yard. The pressure side goes to two return jets at the pool. The owner replaced the motor this week after the other one burnt out.
I have an idea myself what the problem could be just because I have 4 other infinity edge pools on my route, but I would be very interested to hear what the experts think and what possible solution there could be.