XC90 2005 5 cylinder. Was driving car just started stalling would not start had it towed. When hooked up to a computer and said bad crankshaft sensor. Replaced the crankshaft sensor still no start?.a mechanic put a pressure test on it said I was only getting around 60 to 75 PSI which needed around 150 psi. I'm not too confident with the mechanic I was wondering could it be the timing that went off or something worse as in need a new Pistons?