Mechanically controlled pumps
Mechanically controlled injections pumps are divided in two categories: the in-line type and the distributor type. In-line fuel injection pump The In-line fuel injection pump has the same number of fuel pressure mechanisms (elements) as engine cylinders. This type of pump (including the governor, timer and the feed pump on the pump’s body) is mainly used for medium and large trucks and construction machinery. The pump body is equipped with fuel pressure/feed mechanisms (elements) and injection quantity control mechanisms. Furthermore there is a camshaft to drive these mechanisms. The elements in the pump body feed fuel to each engine cylinder according to the injection order.

Distributor injection pump
The Distributor injection pump has only one fuel pressure mechanism, irrespective of the number of engine cylinders. Instead, it has a distributor designed to distribute the pressurized fuel to each cylinder according to the injection order. All the components, including the governor, timer and feed pump, are built into the pump housing. It is a small and light type of pump that can operate at high speeds which is why it is widely used for small engines.