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Why My Diesel Generator Set Fail to Start

Aug. 04, 2018

During the process of using diesel generators, many customers will find that they often encounter situations where diesel generators cannot be started, which will greatly affect the efficiency of diesel generators. Engineer from Jiangsu Starlight Electricity Equipment Co.,Ltd help everyone analyze the reason and solutions of why diesel generator can not start.

Why My Diesel Generator Set Can Not Start.jpg


I Fuel system malfunction, the diesel engine is driven by the starting motor and does not ignite.

1. There's air in the fuel system.

Check if the fuel line connection is loose and remove air from the fuel system. First unscrew the exhaust screws on the injection pump and the fuel filter and pump the oil with the hand pump until there are no bubbles in the spilled fuel. After, tighten the exhaust screw. Pump oil again, when there is return oil in the tubing, then tighten the hand pump. Loosen the nut of the high pressure tubing at one end of the injector, pry high injection pump plunger spring seat, when there is no bubble in the fuel out of the nozzle, spin the nut, then pry a few more times, so that each cylinder injector is filled with fuel.


2. The fuel line is blocked. Check if the pipeline is unimpeded.

3. Fuel filter block. Clean filter or replace filter.

4. Oil pump does not supply oil or intermittent oil supply. Check that the inlet pipe is leaking, and that the filter screen on the inlet joint is blocked. If no oil is supplied after removal, the intake pipe and oil pump shall be inspected.


5. There is little injection, no spray or no atomization. Remove the injector, connect to the high pressure pump, pry the pump plunger spring, observe the spray situation should be removed and washed. Check and adjust the injection pressure to the specified range or replace the injector coupling on the injector test bench.


6. The control handle of the fuel pump governor is not in the right position. When starting, the handle position should be pushed to the position of no load, rotational speed 700-900r/min.


II Electrical start system failure


1. Faulty wiring or poor contact. Check to see if the wiring is correct and reliable.

2. The battery is short of power. Use batteries with sufficient power or add batteries in parallel.

3. Starting motor brush and commutator have no contact or poor contact. Trim or replace the carbon brush, clean the commutator surface with wood sandpaper, cross-blow, or adjust the pressure of the brush spring.


III Insufficient compression pressure in cylinder, fuel injection is normal but does not ignite and there is fuel in the exhaust pipe


1. Excessive wear of piston ring or cylinder liner.

Replace the piston ring and replace the cylinder liner depending on the wear.

2. The valve leaks.

Check valve clearance, valve spring, valve tube and valve seat sealing, sealing should be repaired and ground.

3. Gas storage gap or combustion chamber volume is too large.

Check if the piston belongs to the model, if necessary, measure the air storage gap or combustion chamber volume.


IV Injection advance angle premature or too late

The diesel engine does not ignite or ignite and then stops.

Check that the injection pump drive shaft joint plate is correct or loose, the non-conformity should be readjusted.


V Gas distribution phase is incorrect

VI Environmental temperature is too low

The starting time is long. According to the actual ambient temperature, the corresponding low temperature starting measures are taken.


How to solve the problem of low environmental temperature? For example, the Shangchai series of diesel engine with intake air preheating auxiliary device is used when starting at low temperature. The device is composed of preheating plug, solenoid valve, oil inlet pipe, electronic controller, temperature sensor, indicator lamp and so on. The device only works when the cooling water temperature is below 0 ℃ (controlled by electronic controller).


Before starting, insert the electric key and switch from OFF position to on position, connect the circuit of preheating auxiliary device, at this time the indicator light is on (preheating plug heating up);


When the indicator light starts to flicker (about 50s), the electric key is transferred from on position to START position to start the diesel engine.


Note: if it does not move or start successfully in 30 seconds after the indicator lights flicker, the electronic controller will automatically cut off the preheating circuit, solenoid valve circuit and indicator lamp circuit, and enter the delay protection. To start again, return the key to the OFF position and repeat the process for 5s.


Note: even low-temperature starting with a starting fluid with a quantitative device can aggravate the wear of the cylinder liner and piston ring.


Warning: do not use starter fluid near open fire, preheater or flame ejector. Do not breathe in the smoke. Excessive starting fluid will damage the diesel engine.


Volatile fuel oil shall not be used as a cold starting auxiliary measure in underground mines or tunnels.


In order to start a diesel generator set successfully, there are many preparation jobs we should do.


1. Check whether the surface of the generator set is cleaned thoroughly, and if there is any loosening of the nuts of the ground nuts, flywheel screws and other sports parts, make it strong enough in time.


2. Check that all parts of the clearance are correct, in particular, carefully check the intake, exhaust valve clearance and pressure relief mechanism clearance to meet the requirements.


3. Put each cylinder in the pressure reducing position, rotate the crankshaft to check if there is any abnormal sound from the operating parts of the cylinder, and if the crankshaft rotates freely, at the same time pump the engine oil into the friction surface, then close the pressure relief mechanism and shake the crankshaft, Check if the cylinder is leaking. If you shake the crankshaft, you feel laborious, indicating normal compression.


4. Check the fuel supply system


A. Check that the vent holes in the fuel tank cover are clear and clean if there is dirt in the hole. Check that the added diesel engine is in accordance with the required license plate, fuel quantity is adequate, and turn on the fuel circuit switch.

B. Open the relief mechanism swing crankshaft, each cylinder should have a crisp injection sound, indicating good injection. If the injection sound is not heard, there may be air in the oil path. At this time, the exhaust screw of the diesel filter and the injection pump can be loosened to remove the air in the oil line.

C. Check for oil leakage in the tubing and joint, and solve the problem in time.

D. Add oil to the fuel injection pump and governor to the specified oil level.

E. Check the condition of the cooling system

1. Check that the cooling water in the tank is adequate. If the water is insufficient, clean soft water should be added.

2. Check the water leakage at the water pipe joint and solve the problem in time.

3. Check that the impeller rotation of the cooling pump is flexible and that the belt is tight and appropriate.

F. Check the lubrication system


1. Check the oil pipe and pipe joints for oil leakage and solve the problem in time.

2. Fill the buttered nozzles with the specified grease.

3. Check the oil content of the oil pan, draw out the oil gauge next to the crankcase, observe whether the height of the oil surface conforms to the prescribed requirements, and add the specified number of oil with different seasons and regions. During inspection, if the oil level is above the specified height, the reasons for the increase in oil should be carefully analyzed. There are usually three reasons:

(1) Add too much oil

(2) The diesel oil leaked into the crankcase and flushed the oil

(3) Cooling water leaks into oil.


G. Check the electrical start system

1. First, check whether the relative density of the starting battery electrolyte is in the range of 1.240 ~ 1.280, if the relative density is less than 1.180, it shows that the battery is insufficient.

2. Check that the wiring is correct.

3. Check for accumulative contamination or oxidation on the battery pole, it should be polished clean.

4. Check that electrical contacts such as starting motors and electromagnetic manipulators are in good condition.


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