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2023年11月16日星期四

How to solve the problem that the diesel engine used in Caterpillar excavators cannot start Cause of failure

 How to solve the problem that the 3126B diesel engine used in Caterpillar excavators cannot start  Cause of failure

 

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  (1) The battery is out of power.  

(2) The battery cable is not firmly connected. 

 (3) There are certain fault codes or event fault codes that prevent the diesel engine from starting. 

 (4) There is no power supply to the ECM. 

 (5) The engine oil level is too low.  

(6) The starting circuit or starter solenoid coil is faulty. 

 (7) The starter is damaged. 

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 (8) The flywheel ring gear is excessively worn.

  (9) The intake air heater of the starting auxiliary device is faulty.  

(10) The diesel engine parking switch is in the ON position. 

 (11) The speed/timing sensor is faulty, incorrectly installed and needs calibration. 

 (12) The fuel injection drive pressure is abnormal. 

 (13) The fuel injector does not work.

  (14) There is a fault in the fuel supply system. 

 (15) Combustion failure.

  (16) The internal parts of the diesel engine are bent or stuck.

 

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2. Check diesel engine speed/timing  
 
(1), crank the diesel engine and observe the diesel engine speed on the ET screen. If ET shows 0 r/mim,
 
 then check the speed/timing sensor. Note: When cranking for the first time, the diesel engine speed 
 
signal may be abnormal. Once the ECM can calculate the diesel engine speed from the signal, this 
 
information is replaced with the diesel engine speed. 
 
 (2) Check the diesel engine speed/timing sensor calibration.  
 
(3) Confirm that the timing reference gear is installed correctly. If the gear is installed backwards, the 
 
diesel engine will not start. Check for correct positioning between crankshaft and camshaft drive gear.
 
  If necessary, correct positioning and/or replace drive gear.
 
 
3. Check the injection drive pressure 
 
(1) Check the engine oil level.  
 
(2) If the diesel engine has been repaired recently, there may be air in the injection drive pressure 
 
circuit. Allow the diesel engine to warm up completely and operate the engine under load to bleed the 
 
air from the injection drive pressure circuit. 
 
 (3) Compare the actual driving pressure on the ET with the required driving pressure. If the difference 
 
between the two readings during the fault does not exceed 2MPa, it means that the problem does not lie 
 
in the injection driving pressure circuit. (3). 
 
 (4) Check the sealing condition of the injection drive pressure control valve. If there is a seal failure 
 
then replace the seal and repeat the steps 
 
 (5) Check whether the wiring harness connected to the injection drive pressure control valve is open 
 
and/or short-circuited. 
 
 (6) Measure the coil resistance of the injection drive pressure control valve, it should be 4~162, 
 
otherwise, replace the injection drive pressure control valve. Can leak.
 

4. Check the fuel system 
 
 (1) Visually check the fuel level, do not rely solely on the fuel gauge. Add fuel if necessary. If a diesel 
 
engine runs out of fuel, the air must be bled from the fuel system. 
 
 (2) Check the fuel pipe for problems such as throttling, collapse, and pinched pipes. If the fuel line is 
 
faulty, repair or replace it. 
 
 (3) Check whether there are any foreign objects in the fuel tank. Foreign objects will hinder the fuel 
 
supply.  
 
(4) After replacing the fuel filter, repairing the low-pressure fuel supply circuit, or replacing the 
 
injector, check whether there is air in the low-pressure fuel supply system. You can use the observation 
 
window in the low-pressure fuel supply line to determine whether there is air in the fuel. Note: Do not 
 
crank the diesel engine continuously for more than 30 seconds. Before cranking the diesel engine again,
 
 let the starter cool down for 2 minutes. 
 
 (5) Bleed the air from the low-pressure fuel supply circuit. 
 
 (6) Check the fuel quality. If the temperature is below 0°C, check for solidified fuel (wax). 
 
 (7) When cranking the diesel engine, check the fuel pressure behind the fuel filter. If the fuel pressure 
 
is low, replace the fuel filter. If the fuel pressure is still low, check the fuel transfer pump, fuel transfer 
 
pump coupling and fuel pressure regulator valve.
 
5.Other inspections 
 
 (1) There are certain fault codes and/or event fault codes that will prevent the diesel engine from 
 
starting. Connect the ET and check for current fault codes and/or historical fault codes. Before 
 
continuing with this procedure, troubleshoot and troubleshoot existing fault codes. Note: If the ET 
 
cannot communicate with the ECM, the problem most likely lies in the power supply to the ECM. 
 
Please refer to Section 11.5 of this chapter. 
 
 (2) Check the engine oil level. Add engine oil if necessary. 421
 
  (3) Confirm that the air intake heater has reached the on position. 
 
 (4) The diesel engine parking switch should be in the OFF position. Use ET to check the status of the 
 
diesel engine parking switch. When parking, the ignition key switch should be turned to the OFF 
 
position for at least 15 minutes before the diesel engine can be started again.

 

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