5. Fault Judgment and Elimination of Cummins Diesel Engine

The release date: 2021-05-20

If you have Cummins diesel power generator, maybe you meet some problems in its diesel engine.

1.Why diesel engine starts up more difficult in winter?

Start-up of diesel engine, not only depends on itself technical situation, but also is influenced by ambient air temperature. Here is the reason as follows:


A.In winter, the climate is cold, the ambient temperature is low, the oil viscosity increases, and the friction resistance of the moving parts increases, which reduces the starting speed and makes it difficult to start;


B.The capacity of storage battery decreases with the decrease of temperature, which further reduces the starting speed;


C.Because of low speed of start-up, leakage of compressed air increasing and heat dissipation of cylinder wall increasing, the temperature and pressure of air at the end of compression are greatly reduced, and the delay period of diesel ignition is increased, even if it is serious, it can not be burned;


D.Diesel oil viscosity increases in low temperature, so that injection velocity speed decreases, and at the end of air compression, the whirlwind speed, temperature and pressure of air are relatively low, which makes the quality of diesel fuel injected into the cylinder poor. It is difficult to form a good combustible gas with air quickly and ignite in time, even can not ignite, leading to difficulty in starting.

2.The good conditions of diesel engine start-up

A.Must have enough start-up speed. If starting speed is high, there will be less gas leakage in cylinder, time of heat transfer from compressed air to cylinder wall will be shorter, will loss less heat, so that gas temperature and pressure at the end of air compression is higher. In generally, the speed is more than 100 r/min;


B.The cylinder needs better sealing. This can further reduce the air leakage, ensure that the gas has enough combustion temperature and pressure at the end of air compression, and the compression pressure of the cylinder should not be less than 80% of the standard value;


C.It is required that the fit clearance between the engine and the engine parts be appropriate and lubricated well;

D.Batteries should have sufficient starting capacitance and the starting circuit is in normal technical condition;


E.Starting oil quantity is in accordance with the regulations, injection quality is good, and injection advance angle should meet the requirements;

F. Use standard fuel oil.


3.When starting diesel engine for power generation, crankshaft is failure to turn round.

When diesel engine starts up with a good starting systems, if the transmission is in neutral position and press the starter switch, the starter is noisy while the crankshaft cannot rotate, it means a mechanical fault. The causes of engine crankshaft failure and the diagnosis and repair methods are described below:


(1)The causes

A.Starter and flywheel teeth engage badly. The impact between the ring gear and the starter gear will occur when starting the engine, resulting in tooth damage or one-sided tooth wear. If the teeth are damaged or worn seriously for more than three pieces, it is difficult for the starter gear to mesh with the ring teeth.


B.When the temperature of the engine is too high, the engine stops and extinguishes, and the heat is difficult to dissipate. The piston ring and the cylinder adhere to each other at high temperature, so the engine of diesel generator can not start after cooling.


C.Because of the lubrication system failure or oil shortage, the sliding bearings dry friction, so that ultimately lock the crankshaft and can not start.

D.Injection pump plunger stuck.


(2)The methods of diagnosis and repair

A.If the flywheel has more than three consecutive teeth damaged, and the starter teeth are exactly opposite, the two gears will not mesh. In this state, the flywheel can start smoothly by prying an angle with a crowbar and pressing the start button. For damaged flywheel teeth, welding repair can be generally used;


B.When gear ring is loose, can check installation port of flywheel shell starter. If gear ring is loose, need to replace a new. When install, should heat the gear ring in heater box, and then press on flywheel with heat gear ring, after cooling, can fasten on flywheel;


C.When gear ring teeth is damaged seriously, can press gear ring, after overturn front end face of gear ring, then can install on flywheel;


D.After check meshing of gears normal, when starting can not turn. The reason is engine internal faults, such as crankshaft locking, piston sticking cylinder, clutch sticking, etc., should further observe. Can check whether the clutch is damaged or not, and then check whether the plunger of the fuel injection pump is stuck and whether there is foreign matter in the engine.

4.Diesel engine can turn round, but can not start up

When starting the engine, the exhaust pipe exhausts smokeless, and there is no explosion sound. Generally, diesel oil does not enter the cylinder.


(1)The causes

A.There is not diesel oil in fuel tank;

B.There is some blockage in fuel filter and oil-water separator ;

C.No oil supply in low pressure oil pipeline;

D.Injection pump does not pump oil;

E.There is air in oil pipeline;

F.Valve timing misalignment. The opening time of the valve is inconsistent with the piston's stroke in the cylinder. For example, when the piston is compressed in the cylinder, the intake and exhaust valves are open, and fresh air is driven out of the cylinder, so that there is no combustion gas in the cylinder and it can not start;

G.The solenoid valve of the fuel injection pump is damaged and in a closed state. Diesel oil can not enter the high pressure chamber.


(2)How to solve?

A.Check whether the extinguishing line of fuel injection pump is returned;

B.Check whether the fuel tank has oil, whether the fuel tank switch is on or not;

C.Whether the fastening bolts of the control rod and drive connecting disc of the fuel injection pump have fallen off or not;

D.Unscrew the bleeding screw on the injection pump and exhaust the oil with the hand pump;

E.Check whether the tubing is leaking or blocked;

F.heck whether the fuel filter and oil-water separator are blocked;

G.Diesel engine turns driven by the starter, check whether the pump is pumping oil or not;

H.Remove and loosen the nozzle joint of the injector, add the throttle to the end, press the starter switch, check whether the fuel injection pump is pumping oil or not, if not, indicate that the fuel regulating rod is stuck in the stop position ( rack hairpin); if type A pump, the side cover of the fuel injection pump should be removed for inspection and troubleshooting; if type P pump, appropriate measures should be taken to deal with it;

I.Check whether the valve timing is accurate, if not corrected, adjustments should be made.