Combining technical case studies and key maintenance points, Shacman engineers have compiled the following common fault analysis for Shacman CNG Tractors:
I. Engine Fails to Start
Insufficient Gas Pressure
Phenomenon: No signs of ignition during startup, trouble code indicates low gas pressure (e.g., Code 43).
Troubleshooting: Check cylinder pressure, check if the high-pressure shut-off valve is stuck or the solenoid valve is faulty. Replace faulty components.
Ignition System Failure
Phenomenon: Weak or no spark, abnormal ignition coil voltage.
Solution: Replace ignition coil or spark plugs, check wiring connections.
Electrical Circuit Issues
Phenomenon: Blown fuse (e.g., F4 fuse), no signal from ECU.
Troubleshooting: Check the high-pressure solenoid valve protection device for short circuits. Replace damaged components.
II. Insufficient Power
Abnormal Boost Pressure
Phenomenon: RPM drops during climbing, trouble code 72 (Insufficient Boost).
Solution: Check if the air filter is clogged, replace deformed spark plugs, or clean the gas metering valve.
Imbalanced Air-Fuel Ratio
Phenomenon: Low air-fuel ratio reading, high gas consumption.
Troubleshooting: Clean or replace the gas metering valve, check the NGP sensor.
III. Brake System Faults
Brakes Fail to Release
Cause: Trailer valve air crossover or incorrect pipeline connection (e.g., port 11 mistakenly connected to the dryer).
Solution: Correct the air circuit according to the diagram, replace the trailer valve and test drive for verification.
Brake Fluid Leakage
Phenomenon: Brake pedal feels soft, insufficient braking force.
Troubleshooting: Check the sealing of wheel cylinders/master cylinder, replenish brake fluid or replace seals/gaskets.
IV. Cylinder & Gas System Faults
Gas Cylinder Leak
Detection: Locate leak points using soapy water application or a methane leak detector.
Action: Replace valve seals/O-rings, reinstall and conduct a pressure test.
Pressure Regulator Freezing
Prevention: Regularly check the water circulation system to avoid clogging by impurities.
V. Other Typical Faults
Unstable Cruise Control: Check ECU signals or throttle response.
Sudden Stalling: Investigate fuel metering valve nozzle operation or oxygen sensor short circuits.
Maintenance Recommendations for Shacman CNG Tractors:
Prioritize using a diagnostic tool (e.g., Weichai Zhiduoxing II) to read trouble codes.
For complex issues (e.g., ECU programming), contact professional Shacman service engineers.