The Fuel Rail Pump Solenoid Test function can be used to verify the operation of the Fuel Rail Pump Solenoid. This test provides a method for determining whether or not an open circuit or short circuit is present.
Use this procedure to troubleshoot the system when one of the following Diagnostic Codes is active or easily repeated:
1779-05 Fuel Rail #1 Pressure Valve Solenoid current below normal 1779-06 Fuel Rail #1 Pressure Valve Solenoid current above normal
The Fuel Rail Pump Solenoid is used to control the output from the Fuel Rail Pump. The solenoid receives an electrical supply from the ECM. The Fuel Rail Pump Solenoid is then energized when the fuel is required to be pumped into the Fuel Rail. Varying the timing of the voltage to the solenoid controls the fuel delivery from the Fuel Rail Pump.
When the Fuel Rail Pump Solenoid is deactivated, the fuel that is not sent to the fuel rail is returned to the fuel tank.
The fuel Fuel Rail Pump Solenoid forms part of the closed loop control system for the Fuel Rail Pressure in conjunction with the Fuel Rail Pressure Sensor, the ECM and the software. The Fuel Rail Pressure Sensor measures the Fuel Pressure in the High Pressure Fuel Rail. The signal from the Fuel Rail Pressure Sensor is processed by the ECM and software. The measured pressure is compared to the desired Fuel Rail Pressure for the given Engine operating conditions.
If the Fuel Rail Pump Solenoid fails, it is likely that the fuel will not be pumped into the High Pressure Fuel Rail. The Engine will shut down or the Engine will fail to start. The Fuel Rail Pressure can be observed on the status screen of the Electronic Service Tool/ CAT ET.
Diagnostic Code: 1779-5
This Diagnostic Code indicates that the Electronic Control Module (ECM) has detected an open circuit or low current condition in the solenoid for the Fuel Rail Pump.
An electrical fault may prevent the provision of pressure to the Fuel Rail. This may result in the loss of Fuel Injection. If the solenoid for the Fuel Rail Pump fails, it is likely that fuel will not be pumped into the Fuel Rail. The Engine will STOP or the Engine will NOT START.
Here the STEPS:
1). Connect CAT ET Software to the ECM.
2). Open Menu: Diagnostic - Diagnostic Test- Fuel Rail Pump Solenoid Test
Power All or
Start and wait the process until completed (Mode: Powered).
Test Results is Not OK (*Short), indicates that the Fuel Rail Pump Solenoid is damaged/shorted. Note: This test identifies an open circuit or a short circuit for the Fuel Rail Pump Solenoid. The test activates the solenoid while the Engine is not running. A good solenoid will create an audible click when the solenoid is activated. CAT ET indicates the status of the solenoid as
Not OK (Open), or
Not OK (Short).
During the Fuel Rail Pump Solenoid Test, the ECM pulses 105-volt to the solenoid. The pulses are sent at the proper time and for the correct duration for a given Engine load and speed. The ECM monitors the current flow through the circuit for each solenoid. If the current flow is too high or too low, the ECM activates one of the following diagnostic codes:
1779-5 Fuel Rail Pump #1 Output Current Below Normal 1779-6 Fuel Rail Pump #1 Output Current Above Normal 1780-5 Fuel Rail Pump #2 Output Current Below Normal 1780-6 Fuel Rail Pump #2 Output Current Above Normal