1077/14 Internal/External Leakage of the High Pressure Fuel System


This code indicates high leakage in the high pressure fuel system(fuel rail pressure). This light will indicate both the MIL and CEL but with no engine reactions, no de-rate and engine shutdown. This is for a 3 filter fuel system EPA 07/10.


  1. Check for other fault codes. If 1077/14 is present, you must troubleshoot that fault code first as it will trigger this fault code as well.
  2. Perform an automated fuel system integriy check (FSIC) using DDDL.
  • If longer then 35 seconds, perform the same test while road testing the unit. If the Fault code does not come back again, release the unit or obtain driver info of specific situationĀ  fault occurs.
  • If less then 35 seconds, check for internal & external fuel leaks. Repair any faults/damages.
  1. If no leaks are present, perform an Idle speed balance test. Compare values.
  • If any cylinders are above 70% or below -70% remove each Fuel Injector transfer tube one at a time. Install cap tool J-48704 and perform a FSIC test. If the bleed off time is longer then 35 seconds replace the cylinders injectors
  • If no cylinder is above 70% or below -70% then inspect the PLV for leaks, and replace if leaking.

How to check High Pressure fuel system for leaks:

  1. Inspect high pressure pump fuel lines for kinks/damage or loose fittings, Repair as necessary.
  2. Inspect fuel injector tubes and connections at the fuel rail for kinks/damage or loose fittings. Repair as necessary.
  3. Inspect the fuel rail pressure sensor. Replace if leaking or loose.
  4. Inspect the fuel pump for external leaks (typically at the flanges). Replace if leaking.
  5. Cap all six injectors using tool J-48704, then attempt to start the engine. Using DDDL monitor rail pressure.
  • If rail pressure reaches desired rail pressure, then check rail pressure bleed down. If rail pressure bleeds down a 100 bar in less then five minutes then replace the high pressure fuel pump.
  • If rail pressure does not reach desired rail pressure, then replace the high pressure fuel pump.

PLV leakage checks:

  • Install clear hose to the PLV return line. Cap PLV return line on the fuel filter module. Perform a FSIC test. Any flow out the PLV indicates internal leakage. Replace the PLV and reset the PLV counter to 0.


4 thoughts on “1077/14 Internal/External Leakage of the High Pressure Fuel System

  1. Ron

    After 30 min. The engine loses power. Already replaced def pump, and injector harness. Per freightliner code reading. Still does the same thing.

  2. Mechanic Post author

    Any fault codes present and also check the EGR system for blockage

  3. Tom

    I have a DD15 SCR input Nox sensor not available code what could be the cause changed input sensor and no change

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