Disconnecting a piezo common rail injector while the engine running is highly dangerous and can kill. Unlike with old-style rotary diesel pumps, Piezo injectors work by passing a current through a piezo stack in one direction to expand the piezo crystals then discharge them to the ground to contract back to the original size, this expansion and contraction operate a servo valve, this servo valve controls fuel pressure above the injector needle.

The piezo injectors are operated by up to 200 volts, 15 amps. This has the potential to kill and if you manage to disconnect the injector while the piezo crystals are expanding, the crystals will not complete the process and discharge to the ground causing them to remain in their expanded stake, keeping the injector open.

The fuel pressure within the rail can be as high as 2000 bar at higher engine speeds/loads, even at idle it will be several hundred bars. At this high pressure, the engine would not be able to burn the excessive amount of fuel being continuously injected and it would only take a few engine revolutions to spray enough fuel into the combustion chamber to cause the hydraulic lock and serious engine damage.

PF Jones technicians are fully trained to operate piezo and solenoid operated common rail injectors.