Lesson 2/Learning Event 1
Multiple-Unit Injection Pump System
In the multiple-unit injection pump system, each cylinder has an individual injection pump which meters the
fuel and delivers it under high pressure to the spray nozzle, which leads into the combustion chambers. The
pumps are mounted in a common housing, are operated by a common camshaft, and use the same control
mechanism to ensure an equal amount of fuel in each cylinder at the proper time.
Diesel fuel oil flows from the supply tank through a fuel filter to the fuel supply pump. The fuel supply
pump forces the fuel through an additional filter to the injection pumps. The fuel injection pumps force a
measured amount of fuel through high-pressure lines to the spray nozzle in the combustion chambers.
Surplus fuel flows from the injection pumps through a check valve on the common housing and returns to
the fuel supply tank.