Kubota P1172 – Engine Control Module (ECM): EPR/CFV Regulation Pressure Lower than Expected

The actual fuel pressure delivered by the Electronic Pressure Regulator (EPR) or Continuous Flow Valve (CFV) is lower than the pressure commanded by the engine computer (actual-commanded pressure is < -2.50 in H2O), which typically initiates a Power Derate 2 and imposes a Low Rev Limit.

• WG1605
• WG1903
• WG2503
• WG3800
• LiuGong CLG2020-2035
• Hyster S120FT
• Genie
• Toro
• Haulotte

1. 1

   Verify that the fuel tank is not empty

2. 2

   Ensure that all manual fuel shut-off valves are fully open

3. 3

   Check for a plugged or heavily restricted fuel filter

4. 4

   Verify that the LPG lock-off valve is functioning and opening completely

5. 5

   Inspect the fuel line routing between the Megajector/EPR and the carburetor/mixer for kinks, restrictions, or leaks

6. 6

   Check the engine cooling system (LPG vaporizers rely on engine coolant to prevent freezing; poor coolant circulation can cause pressure drops)

1. 1

   Verify Fuel Supply

   Fill the fuel tank and open all manual valves. Clear the code and run the engine to see if P1172 returns.

2. 2

   Replace the Fuel Filter

   If the fuel supply is adequate, replace the fuel filter, as a plugged filter is the most common cause of low delivery pressure.

3. 3

   Test the Lock-Off Valve

   Cycle the ignition and listen/feel for the LPG lock-off valve clicking open. If it is sticking or failing to open fully, replace the lock-off valve.

4. 4

   Inspect and Reroute Lines

   Visually inspect the hoses connecting the Megajector/EPR to the mixer. Repair or replace any kinked or leaking lines.

5. 5

   Check Engine Coolant

   Ensure the radiator is full and the water pump is circulating coolant to the vaporizer.

6. 6

   Replace the Megajector/EPR

   If all physical fuel supply components, filters, lines, and the cooling system are operating properly and the code persists, the internal circuitry or actuator of the Megajector/EPR is faulty and the unit must be replaced.