Year, make, model, engine size, mileage...and I promise you'll get a good answer, otherwise not likely.
A bad regulator can indeed cause a no start. Some systems have current sensing in the injector drivers and high line pressure will cause the drivers to go into current limit and not fire because the computer thinks there's a short. Try disconnecting one injector and see if it starts. Disconnecting one or two injectors reduces the load on the drivers and allows the others to fire.
Well the simple answer may be your fuel pump is garbage. If the regulator is bad, it will bypass fuel and/or leak. If the fuel pump is not operating correctly, it may not be moving enough fuel (thus it "stalls" fuel flow before the regulator sees its set bypass pressure) or it may have a leak that bleeds off pressure before it even gets to the regulator.
Test for bad regulator is to plug the return line and VERY quickly check fuel pressure. If pressure spikes to or above regulator pressure, the regulator is bad. If it doesn't spike, you have a bad pump or leak in the lines IN the tank (otherwise you'd see it of course).
No.
Would a bad fuel pressure regulator cause a vehicle not to start? There's spark and fuel. On my car, the regulator is on the end of the fuel injector rail, while the other end of the rail has the hose that supplies the fuel. I disconnected that hose, and fuel definitely gets to the rail/injectors, but when the return line hose on the regulator is disconnected, nothing comes out. Isn't the excess fuel that the injectors don't use come out of that? Could it be bad? And if so, would it cause the car to not start?
