1 Troubleshooting Approach:

1) Regarding power: The low-pressure fuel line, high-pressure fuel line, and intake system are blocked or obstructed, and engine internal faults result in incomplete fuel combustion.

(2) Electrical aspects: abnormal faults in proportional solenoid valves, main pressure sensors, EGR solenoid valves, camshaft position sensors, controllers, and wiring.

(3) Hydraulic System: The hydraulic pump regulator is jammed, and power abnormalities have resulted in a mismatch between the hydraulic system’s power and the engine’s power.

(1) Power: The low-pressure fuel line, high-pressure fuel line, and intake system are blocked, and

The engine body fails, resulting in incomplete fuel combustion.

(2) Electrical: Proportional solenoid valve, main pressure sensor, EGR solenoid valve, cam

Position sensor, controller, and circuit abnormalities

(3) Hydraulic: The hydraulic pump regulator is stuck, and the power supply is abnormal, leading to a mismatch.

between hydraulic system power and engine power

2 Troubleshooting process:

1. Circuit system inspection

A. Display screen data check

(1) After the excavator is powered on and started, the display screen shows an abnormal alarm indicating a problem with P131 EGR zero-point learning. Check the plug of the EGR solenoid valve; the wiring harness associated with the EGR valve is found to be normal.

(2) Cancel the automatic idle speed and enter the engine speed query page. In the 10th gear, the engine will lift the boom to relieve pressure, causing the engine speed to drop by 230 (RPM). This speed drop is abnormal. Cancel the automatic idle speed and enter the engine speed query page. The engine speed in the 11th gear is 1850 rpm, which is normal.

B. Main system pressure and proportional solenoid valve current check

(1) Enter the display screen and check the main system pressure under the 10-level overflow condition. The main system pressure shows a pressure of 249 kg for Pump 1 and 304 kg for Pump 2. The main pressure is abnormal. Inspect the main pressure sensor, the voltage of the main pressure sensor, and the wiring harness for any abnormalities.

Enter the display screen and check the main system pressure in the 10th gear overflow state. The main system pressure shows that the pump 1 pressure is 249 kg and the pump 2 pressure is 304 kg, which is abnormal.

(2) Enter the display screen, and under the overflow state of gear 10, check the current of the main pump proportional solenoid valve. Pump 1 current is 28mA, and pump 2 current is 55mA. The currents are abnormal. Clean the proportional solenoid valve, but the currents remain unchanged. Enter the display screen, under the overflow state of gear 11, check the current of the main pump proportional solenoid valve; pump 1 current is 474mA, and pump 2 current is 473mA—no abnormalities detected.

C. Check boost pressure and common rail pressure

(1) In the 10th gear overflow state, the display shows a common rail pressure of 114 MPa, which is normal. The common rail pressure sensor and the high-pressure oil pump have been ruled out as potential faults.

The common rail pressure of 128 MPa displayed on the screen is normal, and the common rail pressure sensor and high-pressure oil pump are...

ruled out.

(2) In the 10th gear overflow state, the display shows that the boost pressure is normal. When the 10th gear overflows, the display indicates that the boost pressure is normal.

2. Main pump power check

(1) Adjust the pressure of the main relief valve to 1,307 kg for pump 1 and 3,500 kg for pump 2.

(2) Replace the regulator of pump 2; the pressure of pump 2 returns to normal. Adjust the pressure of pump 1 to 341 KG and the pressure of pump 2 to 342 KG. The proportional current for pump 1 and pump 2 returns to 462 mA. Both pump pressure and current return to normal, thus eliminating the hydraulic pump fault. Replace the regulator of pump 2, and the pressure of pump 2 returns to normal. Adjust the pressure of pump 1 to 341 KG, pump 2 to 342 KG, pump 1 and pump 2 proportional current to 462 MA, pump pressure and current to normal, and troubleshoot the hydraulic pump.

3. Power system inspection

A. Low-pressure oil circuit inspection

1) After checking the oil-water separator, we found that the filter element was clogged. After replacing both the water separator and the fuel filter element, the fault remained unchanged, ruling out a filter-element failure.

It was found that the filter element was clogged. After replacing the water separator and fuel filter element, the fault remained unchanged, and the

The filter element fault was eliminated.

(2) Remove the oil inlet pipe of the first water separator. The fuel level is normal, ruling out a fault in the fuel line between the fuel tank and the oil-water separator. Remove the first water separator oil inlet.

Pipe: The fuel level is normal; eliminate the oil line fault between the fuel tank and the oil-water separator.

(3) Remove the oil inlet pipe of the high-pressure oil pump. With power applied, the outlet flow is normal, ruling out any faults in the entire low-pressure oil circuit.

The outlet volume is normal when the power is on, and the fault of the entire low-pressure oil circuit is eliminated.

B. Inspection of the air pre-filter, air filter element, and intake pipe

Check the air pre-filter, air filter element, and air intake pipe.

(1) Replace the air filter and eliminate the blockage of the air filter.

(2) Check the air pre-filter to the air filter element, the air filter element to the turbocharger pipes, and the pipe clamps for any abnormalities.

C. Clean the EGR

Cleaning EGR

(1) Remove the solenoid valve of the EGR valve and find that the solenoid valve is stuck.

(2) Clean the EGR valve, from the 10th gear to the overflow state. During commissioning, the engine speed drops normally, and the vehicle’s overall speed is also normal. Job completed. Clean the EGR valve, from the 10th gear to the overflow state, the engine speed of the commissioning is normal, and the speed of the whole vehicle is normal, so it is finished.

Four: Fault Summary

(1) National III engines have relatively high requirements for fuel quality. Poor fuel quality can lead to EGR valve jamming, early wear of the high-pressure fuel pump and fuel injectors, and engine maintenance must be performed on time and in the correct quantities as specified by Sany’s manufacturers.

(2) The air filter needs to be cleaned and replaced in time according to the actual working conditions.

(3) During troubleshooting, perform multiple test runs and, in conjunction with the information displayed on the screen, identify any abnormalities. Follow the principle of tackling easier issues first before moving on to more challenging ones.

When troubleshooting, you should test the car more often, combine the information on the display screen, find the abnormality, and troubleshoot the problem point by point based on the principle of starting with the easy and then the difficult.