Metering Oil Pump Stepping Motor: Description and Operation

Because of rotary engine operating characteristics, a metering oil pump with related distribution hoses and discharge nozzles are utilized to provide adequate combustion chamber lubrication. Rotor apex seals in particular require lubrication in this manner. In order to ensure low emissions while supplying lubrication, the system is ECU controlled via a stepping motor and position sensor. The ECU calculates oil discharge amount based on engine speed, coolant temperature and intake air volume (load).

With position sensor input, the ECU is apprised of pump stepping motor position at all times. This is compared to preprogrammed values as to what is the correct position should be throughout the range of driving conditions, allowing the ECU to detect malfunctions and set a code. If a problem is detected, the ECU will control the pump in fail-safe mode. The pump control pin is fixed at its lowest compensation step and oil is discharged in proportion to engine speed only. If oil injection requirements exceed the lowest compensation step range, fuel injection will be restricted to keep engine speed within oil injection capacity and prevent damage.

The stepping motor is ECU controlled (an output) to provide adequate, but not excessive, metering oil pump discharge that varies as engine operating conditions and emission controls require.