Circuit DescriptionBattery voltage to the fuel pump is passed to the engine control module (ECM) through the controller area network datalink. Component LocationThe voltage measurement is located within the pump control module. Shop Talk1) This fault is set when the fuel pump control module registers a voltage value outside of its threshold limits (6.5 to 18-volt) for 0.5 second.2) The fuel pump fully compensates for voltage fluctuations within its signal range check. Excessive voltage (more than 24-volt) will damage the pump controller.3) Troubleshooting must focus on sources of high or low voltage or engine grounding. Cummins ISB CM550 (1990-94) Fault...

Circuit DescriptionThis fault code indicates that the fuel pump speed/position signal is lost. Component LocationThe speed/position sensor is located in the fuel pump. Shop TalkThe fuel pump determines its speed and position in relation to the engine by referencing aninternal tone wheel gap-analog signals are converted to digital.If the digital signal is not available or if the gap of the incremental angle sensor tone wheel isnot recognized, the pump controller will set a fault code. Also, rapid speed changes, stalling,or inlet pressure under 21 kPa [3 psi] can cause this fault code to set. Cummins ISB CM550 (1990-94) Fault Code:...

Circuit DescriptionThe fuel pump uses an internal check to determine if the fuel injection pump can reach thecommanded timing. Component LocationThe fuel pump circuit is internal to the fuel pump. Shop TalkThe fuel pump uses pressure generated by an internal vane-type transfer pump and its timingsolenoid to vary the fuel pump’s timing according to the specified ECM commands. Possible causescan be classified into four groups:1) Static timing – offset key, gear train issues2) Low-pressure fuel supply issues – restriction issues, low supply pressure3) Fuel pump return plumbing issues – high return restriction, overflow valve issues4) Noise in the engine position...

Circuit DescriptionThe fuel pump uses an internal check to determine if the fuel injection pump can reach thecommanded timing. Component LocationThe fuel pump circuit is internal to the fuel pump. Shop TalkThe fuel pump uses pressure generated by an internal vane-type transfer pump and its timingsolenoid to vary the fuel pump’s timing according to the specified ECM commands. Possible causescan be classified into four groups:1) Static timing – offset key, gear train issues2) Low-pressure fuel supply issues – restriction issues, low supply pressure3) Fuel pump return plumbing issues – high return restriction, overflow valve issues4) Noise in the engine position...

Circuit DescriptionThe engine control module (ECM) receives a signal from the engine speed/position sensor. This signal is then sent to the fuel pump to indicate where top dead center is for each cylinder. Component LocationThe engine speed/position sensor is located on the fuel-pump side of the block, behind the starter. Shop TalkThe fuel pump controller monitors/processes 10- to 12-VDC square wave signals at pin 8 (engine harness pump end). The leading edge of this wave is the top dead center reference for the pump. The reference signal must occur within a defined window. If an engine pulse is not recognized...