the hydraulic release of the single hydraulic circuit of the caterpillar311D LRR excavator

This article introduces the hydraulic release of the single hydraulic circuit of the caterpillar311D LRR excavator

                                                       warn！

The pressure of rolling hot oil or hydraulic oil can cause harm to

personnel.

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After the engine shutdown, the hydraulic oil pressure will

remain in the hydraulic system. Serious injury may occur

without prior pressure release prior to repairs to the

hydraulic system.

When removing the components or lines of the hydraulic

system, ensure that all work machines are lowered to the

ground and that the hydraulic oil temperature is cold. Remove

it only when the engine is stopped and the filler cap is

cooled to manual touch. 

 

pay attention to

During inspection, maintenance, testing, adjusting and

servicing the engine. Prepare a suitable container for

fluid collection before opening or dismantling any stored

parts.

For tools and supplies suitable for the collection and

delivery of liquids on Caterpillar products, see Special

publications, NENG 2500, "Caterpillar Agents Tools

Catalogue."

Dispose of all liquids in accordance with local regulations and

regulations.

Follow the following steps to release the hydraulic pressure from the single

hydraulic circuit of the main hydraulic system.

 

1. Park the machine on the horizontal ground.

 

  

 
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2. Fully withdraw the bucket rod cylinder connecting rod. Adjust the bucket

position so that the bucket is parallel to the ground. Lower the boom

until the bucket falls horizontally on the ground. See the illustration

1.

 

3. Turn off the engine. 

 

4. Turn the engine start switch to the on position, but not starting the

engine.

 

5. Place the hydraulic start control lever in the unlock position. 

 

6. Move only the joystick or pedal of the repaired hydraulic loop to the

full position. This will only release only the high pressure in this

single hydraulic loop. This will also release any pressure that may

exist in the pilot hydraulic circuit.

Note: If the repaired hydraulic circuit needs to start the operating

switch, start the corresponding operating switch in the hydraulic

circuit. 

 

7. Place the hydraulic start control lever in the locked position. 

 

8. Turn the engine start switch to the off position. 

 

9. Slowly release the filling port plug on the hydraulic tank to release

the pressure on the hydraulic tank. The fill port plug shall remain

loose for at least 45 seconds. This releases the pressure that may be

present in the return hydraulic circuit. 

 

10. Tighten the filling plug on the hydraulic tank to the specified torque. 

 

11. The pressure in the single hydraulic circuit requiring repair is now 

 

released and the lines and components can be disconnected or removed from

the hydraulic circuit.

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How to Deal with the Alarm and Speed limit of 1400RPM when the Doosan Excavator Engine is Working

This article mainly introduces how to deal with the problem of alarm and speed limit of 1400RPM when the doosan excavator engine is working.

 

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Fault phenomenon:

An alarm occurs during engine operation and the speed is limited to 1400RPM. 

 Inspection Method: 

 1) The vehicle has been working for 2200 hours, the equipment speed limit is 1400rpm, and the fault code retrieved is P1251: fuel balance leakage;

2) Check that the low-pressure oil line pressure is 70kpa, which is on the low side (normally around 90kpa); after cleaning the oil-water separator, the low-pressure pressure has increased, but the fault still occurs from time to time;

3) After low-pressure inspection, check the high-pressure system, connect the software to perform cylinder disconnection test and crankshaft acceleration test. There is no obvious abnormality in the working status of each cylinder;

4) Check that the resistance of the IMV valve is 3.2 ohms and is normal. Since the IMV valve is easy to disassemble, the 2018-04-27 13:49 Wang Xiaobo IMVi valve was replaced first and tested. After replacement, the equipment works normally.  

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When the P1251 fault code occurs in the engine, the casing should be arranged from simple to difficult. First, check the low-pressure fuel oil line, and then conduct troubleshooting of the high-pressure well rail system.

 

How to Troubleshoot the Problem That the Coolant Temperature of the Excavator's Electronically Injected Diesel Engine is Too High

1. Cause of failure  

(1) The radiator fins are dirty, debris or damaged. 

 (2) Insufficient coolant. 

 (3) The radiator cap or pressure relief valve is damaged.  

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(4) There is air in the cooling system.

 (5) The cooling fan is not working properly and the fan belt is too loose.  

(6) The thermostat is damaged. 

 (7) The cooling system pipeline is blocked or leaking. 

 (8) The coolant temperature gauge is damaged. 

 (9) The water pump impeller is damaged or corroded.

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2.Fault  

(1) Visually inspect the cooling system for broken hoses or other throttling components. 

 (2) Check the radiator fins for dirt, debris and damage. Remove dirt and debris, clean and flush the radiator, and straighten any bent fins. 

 (3) Check the coolant level and add coolant if necessary.

  (4) Check whether the cooling system is leaking and repair the leaking area immediately. 

 (5) Check the cooling system pressure. 

 (6) Check the pressure relief valve and radiator cap. Clean and replace parts if necessary. 

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 (7) Check whether the seat surface of the pressure safety valve and the radiator cover are clean and damaged. 

 (8) Check whether there is combustion gas in the cooling system and whether there are bubbles in the coolant. If there are bubbles, combustion gases may have entered the cooling system.  

(9) Check whether the cooling fan is working normally. Check that the belt and pump are working properly.  

(10) Check whether the thermostat is operating correctly. If necessary, replace the thermostat.  

(11) Compare the coolant temperature reading from the ET to the coolant temperature reading from the mechanical measuring instrument. 

(12) Check whether the water pump impeller is damaged or corroded. Repair or replace water pump if necessary.  

(13) Check whether the fault is caused by system overload, reduce the load and check whether the condition recurs.

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How to Inspect the Caterpillar Excavator Air Intake and Exhaust System

How to inspect the caterpillar325c excavator air intake and exhaust system 

 1. Inspection of air intake and exhaust systems 

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 (1) Inspection of air intake resistance. If there is resistance in the intake and exhaust systems, it will be the 1U-5470 engine pressure assembly (Figure 3-1-46). 

 1) Check the intake pipe and exhaust pipe of the engine air filter to ensure that the pipes are not leaking.

 2) Check the engine air filter element. Use a clean engine air filter

 3) Check whether there are traces of dirt on the clean side of the engine air filter element. If traces of dirt are observed, it means that the contaminants have entered the engine air filter element and/or filter element seal. . NOTE: Hot engine parts can cause burns. Allow the engine and parts to cool before servicing the engine. Contact with a running engine can result in burns from hot parts or damage from rotating parts. When working on a running engine, avoid contact with hot or rotating parts. 

 4) Measure using the differential pressure gauge in the 1U-5470 engine pressure test assembly  

①As shown in Figure 3-1-50, connect the vacuum port of the differential pressure gauge to test position 3. Test location 3 may be anywhere on intake manifold 2 behind engine air filter 4 and in front of wheel booster 1. 

 

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 ②Open the pressure port of the differential pressure gauge to allow it to communicate with the atmosphere. 

 ③Start the engine. Run the engine at high idle speed with no load. 

 ④Record the pressure value, multiply this pressure value by 1.8, and then compare it with the corresponding value below. There is resistance to airflow through an old engine air filter. There will also be some resistance to airflow through a clogged engine air filter. in In the above two cases, the resistance must not exceed 6.2kPa; the resistance of the air flowing through the new air filter element must not exceed 3.7kPa. 

 (2) Inspection of exhaust resistance. Back pressure is the pressure difference between the exhaust pressure at the elbow outlet and the atmospheric pressure. The tools required to check exhaust resistance are 1U-5470 engine pressure components (Figure 3-1-46). NOTE: Hot engine parts can cause burns. Allow the engine and components to cool before servicing the engine. Contact with a running engine can result in burns from hot parts or injury from rotating parts. When working on a running engine, avoid contact with hot or rotating parts. Use the differential pressure gauge in the 1U-5470 Engine Pressure Test Assembly to measure exhaust backpressure. Use the following steps to measure exhaust back pressure. 

 1) As shown in Figure 3-1-51, connect the vacuum port of the differential pressure gauge to test position

 

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    2. Test location 2 may be anywhere on exhaust pipe

 3 behind turbocharger 4 and in front of muffler 

1. 2) Open the pressure port of the differential pressure gauge to allow it to communicate with the atmosphere.  

3) Start the engine. Run the engine at high idle speed with no load. 

 4) Record the pressure value. 

 5) Multiply the value in step 4) by 1.80. 

 6) Compare the value in step 5) with the value below. The exhaust back pressure must not be greater than 10.OkPa.

How to Test a Caterpillar Excavator Unit Injector

 How to test a caterpillar 325C excavator unit injector  

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This step can help determine why the injector is misfiring. 

 

 (1) If you have not yet checked for the presence of air in the fuel, perform the inspection steps and 

 

refer to the "Air in Fuel Test" section. CAUTION: ELECTRIC SHOCK HAZARD. The voltage used 

 

by the electronic unit injector system is 90~120V.  

 

(2) Remove the valve cover and check if there are any broken parts. Repair or replace any broken parts 

 

found. Check all wiring to the solenoid coil. Check to see if the connectors are loose. Also check to see 

 

if the wiring is worn or disconnected. Make sure the connector on the unit injector solenoid coil is well 

 

connected. Perform a tensile test on each wire.

 

  (3) Check for signs of oil leakage. Investigate the cause of the fuel leak. Repair oil leaks.  

 

(4) For the single-piece injector cylinder that is suspected to be faulty, check the adjustment of the valve

 

 clearance. Please refer to the "Inspection and Adjustment of Engine Valve Clearance" section. 

 

 (5) Make sure the bolts holding the unit injector are tightened to the correct torque. To check the 

 

torque, loosen the bolts holding the unit injector. Tighten the bolts to the correct torque. 

 

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 (6) Remove the suspected faulty unit injector and check for signs of coolant leakage. Leaking coolant 

 

can cause corrosion on the fuel injectors. If the unit injector shows signs of leaking coolant, remove the 

 

injector sleeve and inspect it. If the injector sleeve is damaged, replace it. Inspect unit injectors for 

 

excessive brown stains that have spread to the injector tips. If excessive stains are found, check the fuel 

 

quality. Refer to the "Testing of Fuel Quality" section. Replace the seal on the injector and reinstall the 

 

injector. Check for soot accumulation on the surface of the injector seat. If soot accumulates, there is a 

 

gas leak. The cause of the leak should be found and repaired. If the fault is a gas leak, there is no need 

 

to replace the injector. 

 

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 (7) If the fault cannot be solved, replace the faulty injector with a new one.

 

How to Test the Fuel System Pressure of Caterpillar Excavator

  How to test the fuel system pressure of the caterpillar 325C excavator 

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 The tools required to test the fuel system pressure are 1U-5470 engine pressure test assembly, 3Y-2888 

connector and 3J-1970 O-ring seal. NOTE: Both the 5P-2720 Detector Engagement Set and the 

5P-2718 Pressure Detector can be used with these tools. These additional tools will be used later when 

installing the pressure probe. Fuel leaks or splashes on hot surfaces or electrical components can cause 

a fire. Spills should be removed immediately. Keep all parts clean and free of contamination.

  Contaminants can accelerate component wear and shorten their service life. Always be careful not to 

lose fluid when inspecting, maintaining, testing, adjusting, and repairing this equipment. Suitable 

containers should be prepared to collect the liquid before opening any box or disassembling any parts 

containing liquid. All liquids should be handled in compliance with local regulations. The 1U-5470 

engine pressure test assembly is shown in Figure 3-1-46. The 1U-5470 engine pressure test assembly 

can be used to check the engine’s fuel pressure. There is a gauge in the tool set that records the 

 pressure 

in the fuel manifold. The fuel return pipe is shown in Figure 3-1-47,

 and the fuel pressure test is shown in Figure 3-1-48.

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Whether under normal working conditions or under loaded working conditions, the fuel pressure should

 be within the range of 400~525kPa; during low idle speed operation, the fuel pressure at the fuel filter 

inlet should be within the range of 400~435kPa. If the pressure difference △P on both sides of the 

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is ignored, the fuel pressure in fuel supply channel 1 should be equal. For a new fuel filter, the pressure 

differential loss on both sides of it is usually 35kPa. If worn particles accumulate in the fuel filter, the 

pressure difference across it will increase. If the filter becomes clogged, the fuel supply pressure may 

drop to 69kPa before the driver notices significant power loss. If the fuel pressure is lower than normal, 

it will cause cavitation and cause internal damage to the unit injector. The pressure difference on both 

sides of the fuel filter should not exceed 69kPa. Pressure regulator 3 is mounted directly on the 

cylinder 

head. The pressure regulator is located at the fuel return port toward the rear end of fuel supply passage 

1. The oil hole maintains the fuel pressure at low engine speeds.

When checking the fuel pressure on the unfiltered side, follow these steps: 

 (1) Remove the plug from 

 

the fuel pressure gauge port 6. 

 (2) Install the joints, seals and 1U-5470 engine pressure test assembly to

 

the fuel pressure gauge interface 6, so that the pressure of the fuel transfer pump can be measured.

 

  When checking the fuel pressure in fuel supply passage 1, follow the steps below. 

 1) Remove the plug

 

 from fuel pressure gauge port 7. 

 

 2) Install the joints, seals and 1U-5470 engine pressure test assembly

 

 to the fuel pressure gauge interface 7. 3) Run the engine. 

 NOTE: Before checking fuel pressure, make 

 

sure the fuel filter is clean. A clogged fuel filter will cause the pressure at port 7 of the fuel pressure 

 

gauge to be lower than the pressure at port 6 of the fuel pressure gauge.

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