Case IH 755 – ENG (Engine Control Module / Engine ECU): Front Bank injector is bad

Incorrect fueling or a power imbalance was detected on the front bank of cylinders (typically cylinders 1, 2, and 3). It can also be triggered by a fault in the Injector Metering Rail Pressure Sensor Circuit for the front bank.

• MX Magnum
• STX Steiger
• Magnum series
• Steiger series
• MX series
• TG series

1. 1

   Inspect the fuel rail pressure sensor wiring at or near the engine wire harness connector for internal breaks (a common misdiagnosis for this code).

2. 2

   Check the camshaft engine speed sensor and the engine harness connector pins for damage or poor connections.

3. 3

   Monitor the front and rear fuel rail pressure signals using a diagnostic tool (like CNH EASy or Cummins INSITE). Inconsistent values point to an ECM or sensor issue; consistent but low values indicate a fuel leak or air in the system.

4. 4

   Perform an electronic cylinder cut-out test to isolate exactly which injector on the front bank is failing or causing the power imbalance.

1. 1

   Prep and Access

   Remove the valve cover and the rocker shaft assemblies to gain access to the injectors.

2. 2

   Remove the Injector

   Carefully extract the faulty injector from the cylinder head. Inspect the injector and the cylinder head bore for signs of abnormal wear, scoring, or damage.

3. 3

   Clean the Bore

   Clean the injector bore using a specialized bore brush. Place a shop towel on the brush to help pull soot and debris out of the bore. Note: Do not blow compressed air into the injector hole, as this can force debris down into the cylinder.

4. 4

   Prepare the New Injector

   If reusing an injector, replace all O-rings. Ensure the different-sized O-rings are seated in their correct, respective grooves. Lubricate the O-rings generously with clean engine oil.

5. 5

   Installation

   Carefully align and seat the new injector into the bore.

6. 6

   Torque

   Tighten the injector hold-down bolts to the manufacturer's specification (e.g., 59 ft-lbs for specific 15L engines, but you must verify the exact torque spec for your specific engine serial number via QuickServe or your shop manual).

7. 7

   Reassembly

   Reinstall the rocker shaft assemblies.

8. 8

   Set Lash

   Crucially, you must set the valve and injector lash (overhead settings) to factory specifications before starting the engine.

9. 9

   Clear Codes

   Clear the ENG 755 fault code and test run the machine to verify the repair.