Case IH 3633 – Engine Control Unit (ECU) / EDC (Electronic Diesel Control): Fuel in Oil delayed expected reaction

The engine control unit detects fuel dilution in the engine oil, which raises the fluid level and increases pressure in the crankcase. The system attempts to protect the engine by reducing torque, but logs code 3633 if there is a delay in correcting the underlying fault or a delay in the expected torque reduction response.

• Case IH Steiger Tractors (350 to 600 horsepower)
• Case IH Combines (5140, 6140, 6150, 7140, 7150, 7240, 8240, 9240, 9250)
• Case IH Farmall Tractors
• Case IH CVX Tractors

1. 1

   Check the Engine Oil Level: Verify if the engine oil level is over full, which strongly indicates that fuel has contaminated the oil.

2. 2

   Inspect for Fuel Leaks: If the oil level is high, perform a fuel system leakage test to inspect the engine's internal fuel system (such as injectors or the high-pressure pump) for leaks.

3. 3

   Inspect the Crankcase Pressure Sensor: If the oil level is correct and uncontaminated, check the crankcase pressure sensor, its wiring harness, and all connector pins for damage, corrosion, or loose connections.

4. 4

   Check the Venting Valve: Ensure the electrically controlled crankcase venting valve (Fuel in Oil valve) is not mechanically blocked or stuck open.

1. 1

   Clear and Recheck

   Use the Electronic Service Tool (EST) to clear the fault code. Run the machine and recheck. If the code was simply a delay in correcting a previous code, it may not return.

2. 2

   Address Fuel Contamination

   If the code reappears and the oil level is high/smells of fuel, you must locate and repair the internal fuel leak (e.g., replacing leaking fuel injectors or pump seals).

3. 3

   Change the Oil

   Drain the contaminated engine oil and remove the oil filter. Refill the engine with fresh, uncontaminated oil to the correct level.

4. 4

   Repair Wiring

   If the oil was not contaminated, test the continuity between the crankcase pressure sensor and the ECU. Repair any shorts or open circuits in the wiring harness.

5. 5

   Replace the Sensor

   If no defects are found in the wiring or connections and the oil is clean, the crankcase pressure sensor is providing a false reading and must be replaced.