Hello i have a 1998 GT3 with the Kesley Hayes system. But
The "dreaded switch" that is mentioned.
May I suggest this as a possibility.
Use a Diesel common rail pressure sensor - lots of pressure headroom.
Some signal conditioning to provide pump on/off switching at desired pressures with relay contact for output.
Low pressure alarm relay contact.
Analog scaled pressure output- to aid diagnostics.
Would anyone like to contribute a knackered switch so that a fluid adaptor can be engineered?