Fuel injected engine cranks but hard to start and now won't start at all; has spark at plugs, ignition coil resistances normal; injectors and resistor pack resistances normal; new fuel filter; cap and rotor ok; fuel pump hums for few seconds when ignition turned on so it's getting power; main relay, harness, and all fuses ok; fuel output from pressure regulator return hose should be 7.8 ounces but puts out less than 2 ounces when ignition turned on for 10 seconds; recent plug and wire replacement; starter spray ineffective; when it could be started it ran ok but tendency to stall unless constant pressure on gas pedal, loses power climbing hills