Maintenance of Common Rail Diesel Engine after Power Performance Deterioration
Feb 08, 2017
The technical state of the diesel engine gradually deteriorates with the increase of working time, causing its power performance to deteriorate. The main manifestations are: weak engine operation, difficulty in starting, increased fuel consumption, black smoke from the exhaust pipe, abnormal noise from moving parts, etc.
1. Poor sealing performance of cylinders or inconsistent sealing performance of each cylinder
The cylinder pressure gauge can be used to measure the pressure cylinder by cylinder to find out the cylinder with poor sealing. Check the tightness of the valve and valve seat, grind, correct or replace the valve or valve seat as necessary; check the wear of the piston, piston ring and cylinder liner, replace new parts if necessary; check the cylinder gasket, cylinder head and cylinder block Whether there is damage or cracks, repair or replace with new parts.
2. Diesel engine compression ratio is reduced
The main factor for the reduction of the compression ratio is that the valve sag exceeds the maximum limit value, and the valve or valve seat should be replaced. If the center distance between the big and small end holes of the connecting rod is less than the allowable value, the connecting rod should be repaired or replaced.
3. Individual cylinders do not work well or do not work
The cause and location of the fault can be identified and determined by means of listening, temperature sensing, pulse or cylinder breakage.This fault mainly comes from the oil supply system. The common fault is that there is air in the oil circuit or the fuel injection pump and the fuel injector work abnormally.Check and exhaust the air in the oil circuit; check the technical condition of the oil supply components, and replace the plunger spring as needed; grind or replace the plunger, oil outlet valve and needle valve coupler; adjust the fuel injection pressure of the injector and replace Injector pressure regulating spring or ejector rod to remove carbon deposits and blockages at its injection holes and oil return holes.
4. The injection time is too early or too late
First, check the fuel supply advance angle and adjust it reasonably; secondly, check the working condition of the fuel supply device to eliminate the inaccuracy of the fuel injection time caused by the wear or improper adjustment of the fuel supply device.For example, the serious wear of the plunger and the oil outlet valve will cause the fuel injection time to be delayed; if the fuel injection pressure of the injector is too low, the fuel injection time will be advanced and the diesel fuel atomization will be poor.
5. Insufficient diesel or air supply
The oil supply and gas supply pipelines should be inspected and eliminated one by one in the order of the outside and the inside. If the governor is damaged due to long-term use, resulting in malfunction, or the fuel supply is reduced due to improper adjustment, the governor should be re-inspected, repaired and adjusted; If the oil supply and air supply are reduced due to blockage or leakage, the location should be identified and dredged or repaired.
6. Incorrect valve timing and valve clearance
Check and adjust the valve timing and valve clearance. When the camshaft and its bushings and other parts are seriously worn, the valve lift height is reduced, the valve opening time and the opening overlap time of the intake and exhaust valves are shortened, resulting in inaccurate valve timing.
When adjusting, take the intake advance angle and exhaust retardation angle as the benchmark to ensure the best valve timing. Under this advance, the valve clearance is appropriately reduced. The valve clearance is generally greater than 0.2mm, so as not to cause the valve to close loosely and the valve to hit the piston. Otherwise, parts such as camshafts should be repaired or replaced.
7. Poor lubrication and cooling system
The poor lubrication system is manifested as high or low oil pressure. Check and clean the filter, oil filter and impurities and dirt in the oil circuit, replace the oil or filter element, and check the pressure limiting valve, bypass valve and oil pump. Adjust the oil pressure of the oil pump according to the specified value.
The poor cooling system is manifested as the engine water temperature is too high or too low. Check and tighten fan belts as required, remove scale from radiators and engine water jackets, repair leaks, overhaul water pumps and thermostats, and evacuate or enhance cooling air passing through the radiators.
In addition, too much carbon in the combustion chamber and diesel fuel contains water and other reasons, can also cause poor power performance of diesel engines. The combustion chamber should be cleared of carbon and the water in the diesel fuel should be excluded.
