The FAQ of Diesel Engine


Q1: The user stops the vehicle after it operates for a while, but when inserting the key to start again, there isn't any sound and the motor meter shows normal. The engine doesn't have any reaction?

A1: If the sound of engine can not be heard when starting the engine, there may be some problems of the storage battery owing the electricity or of electric circuit breakdown of the engine.
If the starter motor can rotate but the engine can't be started, that may caused by fuel-supplied deficiency; then you can check whether the fuel supplying system leaks or not, whether the fuel filter element is dirty, clogging or not.

Q2: When the vehicle is started in winter, why the engine trembles?
A2: The engine should be pre-heated before starting at low temperature, which always runs at high idle speed in order to preheat. The possibility of cold-start shaking is caused by the carbon deposit and dirt generated deactivation of idling air inflow, or the small quantity of fuel injection caused by obstruction of fuel injector hole, or few fuel injection caused by signals of engine coolant temperature sensor. As the temperature increases, the idle speed returned to normal. We suggest driving the vehicle to service station for inspection.


Q3: What's the operating requirement for automotive antifreeze?
A3: Different types of antifreeze can't be mixed in usage process. Currently in widespread use of antifreeze is glycol type, but there are also other types, such as glycerin. Different anti-freezing agent is added different preservative and lubricant. If mixed these different types' that will freeze and corrode the engine easily.


Q4: Why the oil pressure is too low?

A4: As for engine oil pressure is too low, that can be known mainly from the following five aspects.
1) The oil quantity is improper: it includes the insufficiency of oil, the incorrect oil grade, the engine oil of a low viscosity, the high engine-oil-temperature.
2) Poor lubrication system: the leakage of lubricating pipelines joints, the severe wear of oil pump, the blocking of suction filter.
3) The Engine bearing clearance: The crankshaft bearing clearance, the camshaft bearing clearance, the connecting rod bearing clearance is big.
4) Engine Oil signal device: the Oil pressure sensor failure.
5) The poor oil filter: the oil filter is dirty or blocked.


Q5: When the vehicle running in normal speed, why there is the black smoke come form exhaust pipe?
A5: This problem can be analyzed from the following several aspects:
1) The Air in-flow insufficiency: Check whether the filter clogged, if clogged, then clean or replace it.
2) Fuel is overmuch or uneven: Check the injector.
3) Poor atomizing or injector drops fuel: Please check and repair fuel injector.
4) The delayed injection advance angle: Adjust the injection advance angle or increase the injection advance angle.
5) The insufficiency of compression pressure: Check the air cylinder compression pressure, if it is insufficient, then the Piston Ring and the Cylinder Liner should be replaced.
6) Poor fuel quality. Please replace qualified fuel.
7) Overload running frequently. Run discontinuously or reduce loading.
8) Burning oil. Check piston and cylinder; replace them when they should be replaced.


Q6: When diesel engine runs in normal speed and with normal load, why there is some blue smoke exhausted?
A6: the cause of the blue smoke emitting from diesel engine is that the engine oil entering the combustion chamber which is heated and then evaporate into oil gas.  The main reasons are as follows:
1) The engine oil was filled too much that make the liquid level too high.
2) The big cylinder clearance. The poor cylinder finish. Piston ring scuffing, the small piston ring tension, and installing the piston ring backward may cause oil pumping.
3) The inlet valve becomes loose with valve pipeline.


Q7: When the diesel engine is in normal operation condition, why the exhaust gas with white smoke?
A7: Engine ejecting white smoke, generally speaking, it is caused by engine fuel steam without burning or the reason that there is some water in fuel.  When the diesel oil can't fire through atomization or evaporation in the cylinder, the evaporating fuel formed ivory smoke. The evaporation is white. When there is poor combustion in the cylinder, and some part of the fuel can't burn, the exhaust fume is hoar. The main reasons for the white smoke exhaust of diesel engine are as follows:
1) There is some water in the diesel oil, or because of the cylinder gasket ablation, cylinder liner or cylinder head ruptured and leaked, which caused the water into the cylinder.
2) The low working temperature of compressed air or the insufficient cylinder compression pressure.
3) The fuel injection and atomization quality is poor.
4) The delayed injection time.


Q8: The influences on the diesel engine when the temperature of cooling water is too high or too low?
A8: when the diesel engine is running, fuel combustion release a great amount of thermal energy, the gas temperature in the cylinder is up to 1800~2000℃. There is only 30%~40% of heat produced by burning that transforms into the mechanical energy, and around 20%~25% of it which is taken away by cooling system. If the cooling system is out of work, and the temperature of cooling water is too high or too low, which can affect the normal running of the diesel engine, even break down or lead to accident.
1)The influences on the diesel engine that are cause by coolant temperature is too high.
a) Poor lubrication
The cooling water temperature of over 95 degrees can make the temperature of lubricate oil rise and then become too thin, the main frication doesn't form of lubricating film, which appear half dry friction and even dry friction. At the same time, because of the high temperature of cylinder, the lubricate oil of cylinder wall easily subject to burning, carbon deposit ; which precipitate wearing parts, and cause serious cylinder-scoring, burning Axis or bearing shell.
b) Fitting clearance damage
If the metal parts of diesel engine are under high temperature for a long time, the intensity, elasticity, and abrasive resistance of that will decline; at the same time, the heat will make the parts expanded and out of shape, that will seriously affect the normal clearance with parts, even stuck.
c) The reduction of volumetric efficiency
 The air in the cylinder is heated and expanded, and air density decreases, pneumatic efficiency drops. Because air volume intake is relatively less, that makes decrease of air-fuel ratio (A/F), inadequate combustion causes tailpipe pours out dark smoke, declination of output power of diesel engine.
2)The influence of diesel engine is caused by low coolant-temperature.
a) Mechanical efficiency losing
Since cooling water temperature is too low, thus lubrication temperature decreases, that also deteriorate the fluidity, which not only increase parts abrasion but also increase the mechanical efficiency losing due to the friction resistance increases.
b) Cause cylinder wall corrosion
If the cylinder temperature is too low, the water steam is easy to condense on the cylinder wall. Diesel combustion generated some combustion products (such as sulfur dioxide) which meets the condensed water on the cylinder wall, where will form Strong corroding agent (sulfurous acid、Sulfuric acid ) which adhere to the cylinder wall. Cylinder wall will subject to strong corrosion, which makes the surface of metal tissue loosen. When the piston and cylinder scraping, the surface coat will come off, or the corrosion spots and pits will turn up on the working face of the cylinder
c) Thermal loss.
If the cylinder temperature is too low, the water coolant shall bring some thermal, since the fuel inadequate combustion, it shall not only flush the oil of the cylinder liner and dilute the oil in the oil sump, but also caused the high fuel consumption and engine power loss.
d) Inadequate combustion
For diesel engine, the temperature of the compressed air at the end of the compress phase is an important condition, if the temperature of the cylinder or piston is too low, it will cause the low ignition temperature, so the fuel can't ignite fully and engine work rudely, the tailpipe with black smoke.


Q9: Why the new diesel engine or the heavy repaired diesel engine should be run-in?
A9: Because the crankshaft and half-bearing, piston ring and piston, piston ring and cylinder liner, lifter and cylinder block (lifer guide) are quite without relative motion between the motion pair of the new engine and the overhaul diesel engine, and on the surface of the moving parts, there is a rough rhombus sharp edges, when the diesel engine rotating, the motion parts will cover with lubricating oil film, in order to prevent the direct friction of the two relative motion pairs. Due to the lozenge pointed part on the surface of the motion parts, those make the lubricating oil film between motion parts hard to form. If the new diesel engine and the overhaul engine is have-loaded and is operated with high speed, the lozenge pointed part on the surface of the motion parts are easy subject to direct friction, which easily causes significant erosion and damage.
The new diesel engine or the overhaul engine can not operate at high speed and with heavy load, which should running in with the limited load (automobile loading capacity), rotational speed limit (auto operation speed) for 60h 2500KM, in order to eliminate the metal rhombus between the surfaces of motion parts, which can make good motion and avoid engine parts causing abnormal wear and damage. 


Q10: The causes for cylinder gasket damage?
A10: Cylinder gasket damage is one of the common faults for the diesel engine. It is an inconvenient and onerous task that changing cylinder gasket, therefore, prolonging the cylinder gasket service life becomes very important. The main causes of the problem are as follows:
1) The tightening torque of cylinder head bolt is uneven, that make the cylinder head gasket can not be fit appropriately.
2) The oil engine fuel is always in the condition that the supply advance angle works untimely, that lead to pressure rise rate of rapid burning period increase. If the pressure rise rate is beyond the allowed range, it is easy to cause blunt cylinder gasket.
3) Cylinder gasket deformation and cylinder liner spigot is not flat, or there are some notches.
4) The poor quality of cylinder head gasket.

Q11: Under what circumstance, the engine knock will happen?
A11: no matter to the diesel engine or gasoline engine, the engine knock is a kind of major failure, which should be carefully checked to find out the cause of knock. Generally speaking, the main causes of knock are as follow:
1) When there is large clearance between piston and cylinder, the knock will happen in the condition of cold engine, and the knock sound is so clear, with the engine temperature rises and the clearance narrows, piston knock is disappearing gradually.
2) In order to prevent connecting rod bumping against the bottom end of cylinder liner, the cylinder liner bottom of diesel engine is short. When the piston reaches to the BDC, the revealed cylinder liner part will be longer, and the piston guidance will decline, so the cylinder knock is easy to occur.
3) If the time of oil injection is too early, that leads to pre-ignition, and then the cylinder knock will happen too.
4)  The sound of piston pin noise can easily confused with cylinder knock sound. When one meet this situation, who should distinguish them carefully. The piston pin noise is in idle speed and medium speed is clear, and that often happens on the topping of the cylinder block. 

Q12: What is the solidification point of diesel oil?
A12: The solidification point refers to the highest temperature when the diesel engine diesel begins to solidify under the experimental condition. When chose the diesel oil, the required solidification temperature should be 3~5℃ lower than the lowest working temperature. From the aspect of using convenience, the lower solidification point the better, however, the lower solidification point, the more dewaxing procedures should be needed, therefore the production cost will be higher, so we can just only produce the diesel oil with different solidification point for the different temperature condition of diesel engine.

Q13: The notices of choosing and buying the Engine Oil?
A13: recently, there are a lot of oil make, especially the imported brands such as Compton, BP-CASTROL, Texaco, Mobil, Exxo and so on. First, we should find out the performance and the characteristic of different kinds of engine oil, Fit Models, avoid willfully using the engine oil without knowing the performance by all means in any circumstance.
In actual use, we mainly choose according to quality level and viscosity, such as s level CF SAE10W-40 which applies to the work condition that the temperature is above -25℃, but if the vehicle works with temperature below -30℃, the driver should choose the same quality level as SAE 5W - 30 or SAE 0W - 30 grades of oil. The diesel engine manufacturers to its using oil of oil have strict regulations; otherwise it will cause diesel early wear.

Q14: What's the reason of too high water temperature?
Q14: High temperature is one of the most common faults of the cooling system, the following is the main causes of the high temperature:
1) Water pump and fan belt loose, belt slip.
2) There will be some problem of high hydraulic pressure, water shortage when the gap between water pump impeller and pump case or casing cover is oversized.
3) The air leakage of water pump, the small quantity of feed water,  although the water pump shaft rotate, water pump impeller is loose to water pump shaft.
4) The thermostat stuck, the big circulation valve can not be opened, or the installation of that is inappropriate.
5) The scale deposit in the cylinder head and cylinders water jacket is too thick, or in the Radiator, there are some scale deposits, which cause less effective heat dissipation.
6) The pipe line clogging and engendering air resistance in the water tube.
7) The TEMP. Meter exists error.

Q15: Why we should use antifreeze? What are the benefits?
A15: In cold region, in order to prevent the diesel engine ruptured with the cold temperature, and reduce the work that water drainage and water adding work so that we use the antifreeze. Now automotive diesel engine has been widely adopted antifreeze and anti-freezing antirust liquid, and markets are on sale, the brand is considerable. Whatever antifreeze, that are mixed with almost 40% Hexane and 60% water.
The advantages of antifreeze are as follows:
1) Reduce the trouble of water drainage and water adding. Even if we forget drainage, there shall not the damage caused by frost crack of cylinder block and cylinder head.
2) Because that the antifreeze have corroding effect on metals, so we add some rust-preventing that can reduce the corroding effect to cylinder block and the cylinder head, water pump and tank.
3) If the coolant evaporated which caused the low fluid levels, just add soft water, which is convenient without any special requirement.

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