Low fuel pressure

Low fuel pressure could be either poor fuel supply to the injectors or the injectors are worn and not holding the fuel pressure. The best way to diagnose this is to look at the fuel supply in 3 areas.

1. A. Low pressure supply from the tank to the fuel injection pump. The supply from the tank to the injection pump via the lift pump should be about 2 to 5 bar (30 to 70 psi).
2. B. Fuel is delivered from the injection pump to the injectors at approx. 175 atmos.
3.  Once the fuel is delivered to the injectors at the relevant pressure it must lift the needle and spray finely atomised fuel into the cylinder.