My 03 Sport Trac got a new fuel pump on friday due to a no start issue. Ran fine until Sunday evening and then started repeating the same problem. Inertia switch is good, fuses and relays have all been replaced just to be safe. Would like to change the fuel pressure regulator but I cant find the darn thing! A diagram of its location would be great and any other advice to fix this problem would be greatly appreciated. Thanks in advance

 

You may be on a wild goose chase looking for the pressure regulator because is located on the fuel pump module in the fuel tank.
It is possible you received a defective pump assy , but it is also possible there is an electrical problem. Many times a poor ground for the fuel pump itself can provide the same symptoms as a bad pump.
Some other causes could be a problem with the security system, or no signal to let the computer know the engine is turning over so activate the fuel pump relay and pump.

 

First question would be..

During a No Start, do you hear the pump run/hum? If it won't start, cycle the key a few times ON/OFF (it's a timed pump run function) and the pump run should be easily heard. If a helper is available, listening through an open fill neck helps to hear the pump if in less than perfect areas or back ground noises.
If it does run the pump, I'd check pressure/volume on the fuel rail to make sure it's spec. and take that off the diagnostic table.

Defective pump,, maybe, most likely not unless an install issue. Possible, yes. Prior to replacing parts, did you check for voltage at/through the inertia? Same with during a No Start, check through the inertia for hot out to the pump. If checks are good, time to move on and look elsewhere..