17. Monitor The FRP While Cranking Test
17. MONITOR THE FRP WHILE CRANKING TESTPurpose:
The purpose of this test is to determine if the high pressure fuel system generates minimum fuel pressure to sustain starting.
Scan Tool - Data List Monitoring
- The scan tool may reset below 9.5 volts.
- Select the parameters indicated from the scan tool parameter list and monitor the fuel pressure.
A reading above the FRP sensor specification indicates high fuel rail pressure with the engine OFF.
Check for exhaust gas in the fuel rail, air in the fuel rail, a biased FRP sensor or an electrical concern.
A reading below the minimum FRP sensor specification indicates low fuel rail pressure during crank.
Check the fuel rails and high pressure fuel lines for leaks.
Recommended Procedure:
- Connect the scan tool.
- Ignition ON, engine OFF.
- Access and monitor the FRP volts PID.
- Record the FRP sensor value with the engine OFF.
- Access and monitor the FRP pressure PID.
- Record the FRP sensor value while the engine is cranking.
Fuel pressure greater than 0.49 volts 0 MPa (0 psi) with the ignition ON, pressure may read high due to exhaust gas in the fuel rail, air in the fuel rail, a biased FRP sensor or an electrical concern. If no concerns are found and the engine does not start, carry out the Glow Plug Mist Test - No Start to continue diagnosis. If the engine has a hard start condition, carry out the Power Balance Test to continue diagnosis. 18. Glow Plug Mist Test - No Start 21. Power Balance Test
Fuel pressure less than 27.58 MPa (4,000 psi) during cranking indicates that the fuel pressure is too low to sustain engine starting. Check the fuel injectors, high pressure fuel injection pump, high pressure fuel supply line to the fuel rails and left and right bank fuel rails for leaks. If any leaks are present, repair as necessary.
Possible Causes:
- High pressure fuel injection pump
- Fuel volume control valve or circuitry
- Fuel pressure control valve or circuitry
- Fuel injectors
Tools Required:
Scan tool