PACCAR MX (2004 Emissions) Fault Code: P1086 Common Rail Fuel Pressure – Increase Too Slow

PACCAR MX (2004 Emissions) Fault Code: P1086 Common Rail Fuel Pressure – Increase Too Slow

SET CONDITIONS:
The PCI ECU (D420) detects that the actual rail pressure is below 150 bar [2176 psi] for more than 5 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs when the rail pressure operating state is: Filling rail (during starting).

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back?
– no, repair successful
– yes, repair unsuccessful

POSSIBLE CAUSES:
A leaking injector sealing ring.

This DTC is mostly the result of a fuel system-related issue for which another fuel system-related DTC is stored Troubleshoot these DTCs first

If no fuel system related DTCs are present:
1. Air present in the fuel system. If the fuel system or parts of it have been emptied during maintenance or repair, this DTC may become active temporarily after the engine is started. If the DTC stays inactive when the engine is running, no further investigation is necessary.
2. Fuel gelling at very low ambient temperatures.
3. An external or internal leakage on the high-pressure fuel system components

ADDITIONAL INFORMATION:
1. The rail pressure is closed-loop controlled. A comparison is made between the requested and actual rail pressure measured by the common rail pressure sensor.

2. The actual rail pressure is measured in the common rail by the common rail pressure sensor (F854)

3. P1086 only indicates that the rail pressure is insufficient during cranking. It is mostly the result of a fuel system related issue for which another fuel system-related DTC is stored. Therefore always check if another fuel-system related DTC was stored on the diagnostic service tool session report just before P1086 was stored. The driver’s complaint and malfunction point of time can help indicate a related DTC. Start investigating these DTCs first.