Starting problem after standing with a hot engine

[EA1191]

Sometimes the engine will not start if it has been standing hot for a time.
Did a test using a variable resistor to replace the temp. sensor. The pump would not run if the temp was 80deg and had to be set below 50deg. After the pump had run the temp could be increased to 100 and it would run. The next day it ran at 100deg first try. The engine was actually cold.
When it will not start I have manually closed the pump relay and had the idea of fitting a push switch in the cabin to pulse power to the pump, but not sure where to connect it, perhaps the cigaret lighter. The circuit shows a connection to the computer power lead on later models. That may activate the pump without the computer control when the starter switch is turned to accessories???
The main problem is suggested to be a leaking valve in the pump because the pressure should be maintained for hours. The pump pumps OK but there could be dirt or something affecting the valves sometimes. Perhaps the pressure regulator?. Some cars have a second pump.
Someone must have fixed this problem. And just what controls the pump relay apart from the temperature and ignition pulse? The TFI ignition module? Is there a simple test?
Just suggestions may not be confirmed because the car is not used much and the problem is intermittent.
Some time ago I had a problem with no power to the starter on the first few turns of the ignition. Others wrote with the same problem but there was no one on the system to tell us that the cause could be a corroded push-on clip on the solenoid.
The car was bought second hand with offers from Ford that if I had a problem I could ask the mechanics at the Ford sales for information. They answered questions but I now know that they knew I was off track and had no intention of making any suggestions which could fix it.