Hello, I have a 1999 Ford Explorer.

Hello,
I have a 1999 Ford Explorer Sport, 2dr, 2wd, 4.0L V6, SOHC. The VIN starts with a “1” and the engine code on the VIN is “E”. I am having a starting problem. Engine will rotate but will not start. When I turn the ignition to the run position, (just to the point where the gauges turn on), the fuel pump will not turn on, yet sometimes it will. Rocking the ignition switch will sometimes get the fuel pump to engage. Jumping the vehicle has gotten the fuel pump to turn on. I have checked, swapped and replaced the fuel relay, PCM relay. I can find no breaks in the wiring. This same problem happened over a year ago and I replaced the PCM relay and the problem stopped. Now it is back and new relays have not helped. If a fuel pump is going bad, would that not mean that the engine would not start, or if it did start it would cause idling and stalling problems while driving? This car runs great once the fuel pump does turn on. No stalling, idling problems at all. Can it be a bad fuel pump if it works once you get it to turn on? The fuel pump seems like it needs a jolt of electricity to get going. Any help would be appreciated.