Hi mate,
minimum pressure should be about 1000 bar. Check crank sensor signal. Check vacuum from high pressure pump to tank. This is a delphi system, no pick up pump, it has a transfer pump in HP pump. The crank sensor, pressure sensor, hp pump then rail are all possibilities. You need to get the kit to test. If not then use volt meter connected to pressure sensor and record voltages and I will check what they should be for each pressure.
HTH
James