Are you looking for why it is difficult to start a diesel car when it is cold or hot in cold winter or summer? Why doesn't the diesel engine start in the morning and why does it smoke white, blue or black smoke? In the article you will find out the reasons why a diesel engine does not start well or not when it is cold or hot, and also why white, blue or black smoke comes out of the exhaust pipe.
Almost all owners of diesel cars are faced with the impossibility of starting the engine in winter or the engine starts poorly - it often stalls. What are the reasons and what to do to start your car without problems?
Features of diesel engine operation
In gasoline units, a mixture of air and fuel is formed, which is injected into the cylinders using an injector. Once in the combustion chamber, the mixture is ignited by a spark plug and a working stroke occurs. Next – release, compression, then the cycle repeats. Unlike gasoline engines, in a diesel engine the mixture is ignited by high pressure. It will enter the combustion chamber using spray nozzles. In addition, the glow plug is switched on, which heats the fuel to the required temperatures.
But if they fail, the diesel unit is unable to start normally. The glow plug significantly simplifies the process of igniting the fuel and, accordingly, starting the engine. If the diesel engine does not, then the control relay is broken and the spark plug does not heat up the diesel fuel. The action of this element does not stop until the coolant temperature reaches operating values. The glow plug often saved car owners when starting the engine in winter.
We also note that, in addition to the ignition method, such engines differ in the design of the fuel system. And if gasoline ones have a simple submersible pump, here there are two of them: one of low pressure and the other of high pressure. Well, let's look at why diesel is not “hot”.
Why is the mileage before engine overhaul reduced?
Fuel injection systems are constantly being improved. The main source of progress in the internal combustion engine is the requirements for the environmental safety of the car. The more completely and efficiently the fuel burns, the higher the engine power becomes with the same volume of the combustion chamber. This is achieved by increasing the fuel injection pressure. Increasing the volume of supplied air when using a turbocharger. All this entails an increase in the combustion temperature of the fuel. And as a result, the engine mileage before major repairs decreases.
Therefore, modern engines fail after a mileage of 100-150 thousand kilometers. And this has nothing to do with the conspiracy of industrialists. We already miss the good old millionaire diesels. High pressure fuel pumps will soon become history. They cannot keep up with the race to meet environmental requirements.
Compression
Initially, its level is two times higher than that of gasoline units. The mixture ignites under strong compression. And a drop in compression does not have the best effect on starting the engine. Since any compression process is accompanied by the release of thermal energy, the mixture does not heat up enough and is not able to ignite. If it is a car with high mileage, compression drops when the cylinder walls wear out and the rings burn out. Recall that each piston has three rings. Two are compression, one is oil scraper. This requires disassembly and repair of the engine. It happens that compression drops in only one of the cylinders. In this case, the diesel engine starts and stalls or troits. This means that one of the cylinders is not working or ignition occurs irregularly.
Bacteriological factor
Unlike gasoline, diesel fuel is a fertile environment for the proliferation of microorganisms and bacteria. This is especially often observed when water gets into the tank - an ideal environment for reproduction. The rapid growth of bacteria causes the appearance of mucus, acids and other potentially dangerous substances that stick together the fuel pump, filters, and injectors. The process is accompanied by abundant formation and release of hydrogen sulfide, so the fuel in the tank has a persistent unpleasant smell of rotten eggs. As the temperature rises, the process of reproduction of microorganisms only intensifies, but the problem is sometimes typical in frosty weather.
To get rid of unwanted guests, it is recommended to completely drain and clean the fuel tank. For this purpose, special additives are used - biocides. A fresh and cleaned tank is treated with biocides for preventive purposes, after which fuel can be poured into it. Fuel wires and the pump are also cleaned if they are dirty.
What is normal compression?
If for gasoline units this figure is from 9 kg/cm², then for diesel units the minimum value is 23 kg/cm². It is measured using a special device - a compression meter.
In this case, the starter must be turned for no more than 3-4 seconds, otherwise the battery will discharge. Already at the first “grabbing” the result will be visible. It will not change with further rotation of the crankshaft.
Causes of poor diesel starting
- Why is it difficult to start when the injector is cold?
- Why is it difficult to start on a cold carburetor?
- Why is it difficult to start on a cold diesel engine?
Reasons why it is difficult to start when cold It is important to distinguish between situations in which problems arise: the car is hot and difficult to start, difficult to start after being idle, when it cools down, (especially in the morning) if it refuses to start in cold weather. They all have their own nuances and reasons that should be considered separately.
We will understand in general terms what reasons lead specifically to poor starting of a cold engine. Usually one or two rotations of the starter armature shaft are enough to start a car in good condition.
If this cannot be done, you need to look for why.
Glow plugs
Why won't the diesel start? The reasons may be hidden in the glow plugs. It is very simple to determine this breakdown - the car starts well only with a warm engine. “When cold,” the starter turns, but the engine does not start due to the unheated combustion chamber. Usually happens in winter.
Also, if the engine was able to start, it will work intermittently. If the diesel engine is bad, several glow plugs may have failed at once.
Quality of diesel engine oil
Lower outside temperatures often cause diesel engines to have difficulty starting in winter. The reason may be that the oil in the diesel crankcase is thick. Diesel engines are often operated on 15W-40 motor oil. At low temperatures, this viscosity indicator can make it difficult to start a diesel engine.
To check, just pull out the oil dipstick and assess the condition of the engine oil after the diesel car has been parked in the cold. The oil on the dipstick should show signs of fluidity. Otherwise, and there is obvious solidification of the oil, it is advisable to switch to a synthetic motor oil with a lower viscosity recommended for a particular engine.
Filters
For what other reasons does a diesel engine not start? Of course, these are filters. It is necessary to check their condition.
There are two levels of purification in the fuel system of a diesel engine - coarse and fine.
The latter needs to be given special attention. The paper cavity of the filter, through which fuel passes to the nozzles, is capable of trapping particles up to 10 microns in size. The resource of this element is 8-10 thousand kilometers. If you do not follow these regulations, the filter will simply become clogged. As a result, fuel will not flow into the combustion chamber, although the pump produces the required pressure. This can be determined by the nature of the vehicle's movement. If there are dips in dynamics, this means that fuel is supplied with a delay. And it is the filter clogged with dirt that delays it. It is worth mentioning the air elements.
Such filters also require replacement. According to regulations, their service life is 10 thousand kilometers.
They are stored in a plastic case; you can replace them yourself by sliding the mounting brackets and removing the cover. The photo above shows what a dirty air filter looks like. Because of this, the diesel engine will not start. The oxygen supply stops or is reduced to a minimum level. The engine does not have enough air - it choke on fuel.
Diesel with Common Rail system will not start
The operation of the Common Rail system is described in detail in this article. In a nutshell, the priming pump from the tank supplies fuel to the high pressure pump. The high pressure pump in the Rail builds up the pressure necessary to ignite the fuel. The injectors, upon command from the control unit, open when the piston is at TDC on the compression stroke.
Structurally, the Common Rail system is the same on all diesel engines. It differs only in shapes and sizes, but the principle of operation does not change. And the causes of the malfunctions are the same.
As an example, I will give you troubleshooting on an ISUZU engine. The engine is installed on a Hitachi ZX 240-3 excavator.
To find the fault, it was necessary to check the performance of all fuel injection systems and ultimately establish the reason why the diesel engine stopped starting. Namely, it was drowned out. and when I tried to start it again, nothing happened.
The fuel injection system has the following design. Fuel is pumped from the tank by a pumping valve installed separately from the engine. The fuel enters the pump through the filter. And through another filter it is supplied directly to the high pressure pump.
Immediately the reasons why the engine may not start are clogged filters. Or the booster pump is faulty.
You can verify that it is working correctly by disconnecting the fuel wire going to the high pressure pump. Turn on the ignition. The fuel will flow into a specially prepared container. One liter of fuel should be pumped in two minutes. Under this condition, the low pressure fuel supply system is considered to be operating properly. The fuel should flow with little pressure and the plastic bottle will fill quickly.
It is also necessary to check that the fuel line is not clogged. The ignition turns on. The tube that goes to the high pressure pump is disconnected. The fuel should also come out of it with low pressure and without air bubbles. That is, there were no questions about the low-pressure fuel supply system.
This system uses an electric boost pump, but most engines use a rotation pump, which only occurs when the engine rotates. It’s more complicated here, but you can still remove air from the system by pumping a mechanical pump, which is installed on a coarse filter.
Checking the high pressure pump.
The low pressure system turned out to be working. Now you need to check the high pressure pump. Any hydraulic pump creates outlet pressure only if resistance is created. That is, if you unscrew the tube from the pump that goes to the rail. And turn the engine with the starter. A working pump will not create the required pressure. And the fuel will splash out of it in small portions.
To make sure the pump is working properly, you need to block the pump outlet with your finger. And when the engine rotates, fuel will begin to knock out from under it. The pump will create pressure that can be held with your finger. This means that the pressure is rising and the pump is working. It is not necessary to check the pump enough to make sure that similar pressure occurs in the high-pressure tubes that extend from the rail to the nozzles.
If you unscrew the tube from the injector and rotate the engine. Fuel should splash out of it under slight pressure. And if you also close the tube with your finger, the pressure will increase slightly and fuel will begin to be thrown out from under your finger. Of course, this method of verification is not one hundred percent accurate. it only allows you to verify that there is fuel in the rail. And the mechanical part of the fuel supply to the injectors works properly. And also that there is no air in the system. The presence of air will not allow the pressure required to start the engine to be created in the system. Even a slight violation of the system's tightness will not allow the system to build up pressure and the engine will not start.
Checking the operation of the injection system by connecting the computer to the computer
At the first stage of troubleshooting, we had to check the presence of fuel in the system. And first make sure that the high-pressure pump is working. As you can see, everything is fine. Now it was necessary to connect to the engine ECU to check the errors that had arisen. Find out the actual fuel pressure in the rail. This could be done immediately. But without a mechanical check, the fuel pressure reading would still raise questions about the tightness of the system. Therefore, it is better to exclude this moment immediately.
After connecting to the ECU, several errors arose regarding CAN bus problems. Similar errors occur if you run the engine for a long time and it does not start. The ECU disables communication between the ECU and the engine's electronic components. That is, the engine does not start and the system protects the engine. Whatever it starts if there is some kind of malfunction. These errors can be removed using a computer. Or they disappear on their own when the ignition is turned off. This is what happened, the errors were removed, but the diesel engine still did not start.
Checking the rail pressure
Using a scanner, you can see what pressure occurs in the rail. A pressure sensor is installed on the main rail. The computer reads readings from it. In our case, when the engine was rotated by the starter, the pressure in the rail rose to 8 MPa. To start the engine, 30 MPa is required.
The fuel pressure sensor may be the source of the problem. Because if a signal does not come from it, the ECU will not give the command to open the injectors. But if the sensor is faulty or the signal from the sensor is incorrect, the scanner will display an error. It is about the malfunction of this sensor. In our case, this did not happen and the sensor is considered to be operational. Although there have been cases when the scanner is silent. The engine will not start. And only replacing the sensor with a working one helps to find the fault. This, of course, cannot happen on an Isuzu engine; it is rather a disease of our engines when the scanner does not correctly read errors.
The search for pressure loss must continue. There are two elements left to check.
· An emergency pressure valve is installed on the rail. It may turn out to be faulty and release the resulting pressure into the return line.
· And the most common way of loss of pressure is a malfunction of the injectors. They do not hold back the incoming pressure from the rail. Fuel begins to flow back through the injectors. It is enough that the injector turns out to be faulty and the engine will not be able to start. So, dumping fuel on one injector will relieve pressure in the rail and pressure will not flow to the working injectors in the same way.
Checking the emergency rail pressure valve.
An emergency release valve for excess pressure is installed on the rail. If even a hair gets under the valve, there will be no pressure in the ramp. It is screwed into the rail, and the return pipe is screwed to it at the outlet. To check that the valve does not release the resulting pressure. It is necessary to unscrew the return pipe. It is advisable to close the tube openings. Because when the starter rotates, fuel will flow out of it. The tube is connected to the common fuel drain system. If there is no leakage from the valve. Then we can conditionally consider it serviceable. At the stage of checking the tightness of the system.
The valve may be the source of the problem. For example, it begins to bleed fuel from the rail at a higher pressure. And if checking the injectors does not give results, then a further problem with starting the engine must be looked for in this valve.
At this stage, we believe that everything is fine with the valve.
Checking common rail injectors
Connecting a scanner and searching for pressure loss has not yet yielded any results. All that remains is to check the injectors for pressure loss. This can be done while the injectors are installed on the engine. It is necessary to determine the amount of fuel that passes through the injectors and enters the return line. What will it give. By the amount of fuel coming from the return of the injectors, you can determine its permissible amount. That is, if it is adjacent to the return line of the injectors. And all the incoming fuel is poured into the flask, you can see how much fuel has arrived in a certain amount of time. Let's say on this engine. At idle speed, no more than 60 ml of fuel should flow from the injectors in one minute.
The return pipe from the head was unscrewed.
Instead of a tube, a fitting with a hose is screwed in. The reverse end, which is placed in a plastic bottle. Of course, it is absolutely impossible to rotate the engine with the starter for 1 minute. They turned it for 10 seconds and, as you can see in the photo, more fuel leaked out than it should have in a minute of engine operation.
That is, there is definitely a malfunction in the injectors.
To solidify your assumption. It is necessary to check which injector flows more than others. The design of the engine allows you to see this. To do this, you need to remove the valve cover. Remove the return pipe. Which is screwed to the injectors and the channel in the head. Rotating the starter shows that one of the injectors is flowing more than the others. There was one working nozzle available. After replacing it, the engine did not start. But the pressure in the rail, according to the scanner, rose from 8 to 14 MPa. That means we are on the right track. To start the engine, all injectors must be replaced. This is what happened after they were replaced. The engine started immediately without any problems.
As can be seen from the example, the diesel engine does not start due to a loss of pressure in the rail due to the fault of the injectors. There may also be other reasons. But the general thing is that the ECU will not give the command to open the injectors until it sees the required pressure in the rail.
Pump
There are two mechanisms in the system. These are fuel injection pump and high pressure fuel pump. Often the first element fails, since its structure is more complex than that of the second. The pump cannot produce the required pressure in the fuel system, which is why the diesel engine does not start or starts with difficulty. The movement is accompanied by “sneezing” (as if the car does not have enough fuel). It is worth noting that a belt is connected to the injection pump. It may tear or fly off. First of all, we check the belt drive. Check the fuel system fuses (which go to the pump). One of them may burn out. This often happens during a short circuit. Experienced motorists are advised to always carry a set of spare fuses in the glove compartment.
Water got into the filter and froze
Another reason why the fuel is not pumped is that water got into it and froze in the filter.
Depending on the design, the fuel filter is maintenance-free (i.e. it must be replaced every 30,000 km) or has a water drain. How much water accumulates in the filter depends on the quality of the fuel, ambient temperature, number of engine cranks, etc. If you do not drain the fuel filter from time to time, severe frost may cause an ice plug to completely block the flow. diesel fuel into the engine. It's worth checking: if the filter in your car has a drain plug, it's worth using it from time to time. In addition, do not delay replacing the fuel filter.
For prevention, you need to keep the tank as full as possible in winter, use winter diesel fuel or add a dehydrogenating additive. Also, many diesel engines have a special drain plug near the fuel filter, which should be used to drain water that accumulates from time to time. It's worth finding out if there is such an element under the hood.
Fuel and winter
Diesel starts especially poorly in the autumn-winter period, when the air temperature drops sharply and “Arctic” fuel has not yet appeared at gas stations. As a result, the summer diesel fuel simply freezes. At low temperatures, it crystallizes and turns into paraffin, which becomes clogged in fuel lines and filters.
Further movement with such a filter as in the photo above is simply impossible. Some cars have filter heating installed. But it only saves at startup. After a couple of seconds the car stalls again. It is very difficult to heat up an entire tank with frozen fuel. Not all cars have a preheater. What is the difference between summer and winter fuel? There are additives that reduce the waxing threshold at low temperatures. To prevent the problem from taking you by surprise, purchase a diesel fuel additive before the onset of cold weather. Experienced motorists recommend not leaving your car in a parking lot with a half-empty tank. Overnight, the liquid condenses and water forms on the walls. It also does not have the best effect on engine starting. In winter, try to maintain the level above half. Moreover, driving on an empty tank often kills the pump. This applies not only to diesel, but also to gasoline cars.
Diesel won't start on a Kamaz car
Here is another example in which an engine with a Common Rail system stopped starting. The Kamaz vehicle has a Euro 4.V engine with a Common Rail injection system. The system has a similar device. The exception is the low pressure boost pump. The pump rotates from the engine. It is installed on a high pressure pump. That is, the pump begins to pump fuel as the engine rotates. This creates certain inconveniences when pumping the low pressure system. But the system is pumped in the same way as in the example above.
The engine was turned off in the evening while parked. And in the morning they couldn’t start it. Before connecting the scanner, we read the low pressure system. We made sure that the high pressure pump is creating pressure. What does the presence of fuel in the rail indicate? That is, when the tubes coming from the injectors are unscrewed, fuel splashes out. The system is filled with fuel and there is no air in it. But all efforts to start the engine were unsuccessful. Moreover, a knocking sound began to be heard in the high-pressure pump.
When connecting the scanner, it was discovered that the pressure in the rail when the engine rotates is released and does not reach the required level for starting.
There is definitely a problem with the high pressure pump.
I had to remove the pump and drive gear. The following was discovered. The key on the gear was cut off in the drive gearbox. When disassembling the pump, it turned out that the plunger was jammed and could not be repaired.
There is a very small chance that the pump may jam. If he doesn't get help. Due to fuel economy and the fear that drivers will waste it on themselves. Even with an electronic control system. Fuel was allocated depending on the route of travel. But there were always moments when the route lengthened and the car did not fit into the norm. Therefore, the fuel often ran out. The engine stalls. When trying to pump the fuel poured into the tank, the pump rotated dry. The savings resulted in expenses of more than 150,000 rubles.
After replacing the gearbox and high-pressure pump, the engine started without problems.
Starter
This problem occurs on both petrol and diesel cars. A relay is also connected to it.
And if the starter does not turn, we listen for clicks, as is the case with the glow plug relay. Perhaps it's an open circuit. Check the battery charge. Of course, it won't be able to drop to such a low level overnight. Even at eight volts it will turn the starter. Slowly, but still. A sharp decrease in level occurs in the event of a short circuit to ground. Perhaps the contact has broken and is shorting out.
Causes of problems - engine wear
In some situations, breakdown of a diesel engine may be caused by wear of the unit or parts of the fuel system.
This provokes a decrease in compression and the engine will either start poorly or not be able to work at all. This is especially noticeable in the cold season, even if the spark plugs are fully operational and the driver uses only high-quality winter fuel. Quite often, the engine is started from a tug and if it is warmed up, it does not cause problems. It is worth noting that a sharp decrease in compression indicates wear of the unit. Then it must be repaired or replaced. You can also understand that the engine is worn out if the fuel oil consumption is increased and the pressure in the crankcase is quite high. In this situation, the only way out is a major engine overhaul.
In addition, the nozzle nozzles may become unusable, which will increase the consumption of diesel fuel, and black smoke will come out of the exhaust pipe. Very rarely, when nozzles break down, you can see acrid white smoke from the exhaust. These parts should be changed in a timely manner, since their service life is about eighty thousand kilometers.
A long period of engine operation with worn nozzles can lead to burnout of the pistons and pre-chambers. Quite often you can encounter situations where the injection pump plunger pairs wear out, which is accompanied by difficulty starting a heated engine. They also need to be changed periodically to avoid motor damage.
Timing belt
Why won't the diesel engine start yet? If the battery is well charged, the starter turns, but does not “grab”, the timing belt may have broken. The system is not able to select the correct phase for each cylinder. Often on 16-valve engines, this failure is accompanied by deformation of the intake and exhaust valves. They bend when the piston hits.
To avoid letting your car get into this state, check the serviceability of the belt. If there are tears or cracks, it must be replaced. Buy original spare parts. The belt is a very important part in a car. According to the regulations, it changes every 70 thousand kilometers. If it is a chain drive, the element may simply stretch or skew one or more teeth. Manufacturers say that the chain in the engine is designed to last the entire life of the engine. But after 200 thousand it stretches - noises are heard during operation. With such symptoms, you need to change it urgently.
The fuel is not quite winter friendly
Diesel fuel that does not meet official winter standards will not allow you to start the engine in the morning after overnight frosts. If paraffin precipitates, the fuel filter or line will clog and the fuel supply will stop.
To avoid troubles, you need to refuel with high-quality winter fuel at proven gas stations. If doubts remain, then it is better to use a special fuel additive and preferably before the onset of frost.
Results
Strong-smelling gray exhaust gas may indicate that the engine's air-fuel mixture is too rich. The fuel level may be too high, for example due to a faulty temperature sensor.
- There are many reasons why a diesel engine does not start in cold weather.
- To successfully combat diesel in winter, you need to prepare for the onset of cold weather:
- charge the battery (replace with a new one), make sure that the generator is in good technical condition
- replacing engine oil and filter
- check the serviceability of the glow plugs
- replace fuel filter
- changing fuel to winter
- drive with a full tank of gas
In most cases, if these measures are followed, problems with starting a diesel engine at low temperatures will not arise.
The article describes the reasons why a diesel car (diesel engine) does not start for the following brands of cars:
However, if the engine does not start cold, try adding warm fuel to the tank or warming up the diesel engine by pointing a construction (household) dryer to the fuel filter and gas tank. After 10-15 minutes, only warm fuel will flow back into the tank, and only then you can hit the road.
If the problem is a discharged battery, try to “ignite” the engine, or better yet, remove, heat and charge the battery.
Club of fans of minibuses and minivans
At high temperatures outside or when the engine is hot, a serviceable diesel engine can be started without glow plugs at all. In severe frost, the purpose of the pre-heating system is not only to facilitate starting, but also to help during the first seconds of warming up. After the “spiral” on the dashboard has died down, the spark plugs continue to work for some time. If you managed to start the internal combustion engine on a frosty morning, albeit off the air, but the engine continues to run unstably for some time, be sure to pay attention to diagnosing the glow plugs.
How to check
- The candle must be turned out of the well;
- connect it directly from the battery (ground to the spark plug body, plus to the bus connection point) and watch it warm up. A working candle necessarily glows from the edge, uniformly changing color as it heats up.
Only such a system will ensure proper starting in cold weather.
