Mitsubishu has developed various types of turbo diesel engines:

1. Injector Pump with mechanical control (eg early versions of the 4d56 and 4m40 engines).
These diesel engines have mechanical injector pumps with no compensation controls.
This means that the throttle acts as a "tap", opening a valve which allows more diesel to be fed to the injectors.
Once the calibration and pump timing is set, the diesel delivery is controlled by throttle setting only.
The only compensation is for high boost situations. The pump has a vacuum valve, activated by boost pressure, that allows more diesel at high boost.


2. Mechanical pumps with electronic control (ECU) (eg later versions of the 4d56 and 4m40 engines, as well as the 4m41 3.2 Di-D engine)
These engines still have mechanical injection pumps, but the timing and volume of the diesel injection is controlled by sensors and a ECU.


3. Common Rail diesel engines (eg the 2007 versions of the 4d56 and the 4m41. The 4m40 seems to have been discontinued)
These engines have no injector pump, but a high pressure pump, that keeps a common rail (manifold) under extremely high pressure.
The timing and volume of the diesel injection is controlled by ECU and sensors. The ECU controls the feed of diesel fuel from the common rail (manifold) to the injectors according to the mapping of the ECU, the sensors, temp, load, speed etc.

The down side of the Common Rail engine is the reliance on very clean diesel fuel. The pressures in the manifold and injectors are similar to those in liquid cutting equipment. Any impurities will erode the injectors very quickly)