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Diesel does not start: possible causes and solutions

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Diesel does not start: possible causes and solutions
Diesel does not start: possible causes and solutions

Imagine the situation. You wake up early in the morning, hurriedly go to the garage and get into the car. You turn the ignition key and … The car does not start. Probably every car owner has faced such a situation. The problem with starting the engine is one of the most unpleasant. After all, you need to go, but the car is standing. There is panic. What to do if the diesel does not start? The reasons and methods for their solution are further in our article.

Diesel engine features

In gasoline units, a mixture of air and fuel is formed, which is injected into the cylinders with the help of an injector. Once in the combustion chamber, the mixture is ignited by a candle and a working stroke occurs. Next - release, compression, then the cycle repeats. Unlike petrol engines, the mixture in a diesel engine is ignited by high pressure. It enters the combustion chamber with the help of spray nozzles. In addition, the glow plug is switched on, which heats the fuel to the required temperatures.

But when they fail, the diesel unit is not able to start normally. The glow plug greatly simplifies the process of igniting the fuel, and, accordingly, starting the engine.If the diesel does not start "cold", then the control relay has broken and the candle does not heat up the diesel fuel. The action of this element does not stop until the temperature of the coolant reaches operating values. The glow plug has 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 there is a simple submersible pump in gasoline pumps, then there are two of them: one is low, and the second is high pressure. Well, let's look at why the diesel does not start "cold" and "hot".


Initially, its level is twice as high as that of gasoline units. The mixture ignites from strong compression. And the 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, the compression drops when the cylinder walls wear out and the rings burn out. Recall that each piston has three rings. Two compression, one - oil scraper. This requires disassembly and repair of the engine. It happens that the compression drops in only one of the cylinders. In this case, the diesel engine starts and stalls or troit. This means that one of the cylinders is not working or the ignition is irregular.

What is normal compression?

If for gasoline units this indicator is from 9 kg / cm², then for diesel units the minimumvalue - 23 kg / cm². It is measured using a special device - a compression gauge.

diesel won't start

The starter must be turned for no more than 3-4 seconds, otherwise the battery will be discharged. Already at the first "grasping" the result will be visible. With further rotations of the crankshaft, it will not change.

Glow Plugs

Why won't diesel start? The reasons may be hiding in the glow plugs. It is very simple to determine this breakdown - the car starts up well only on a warm engine. The starter turns "on a cold", but the engine does not start due to an unheated combustion chamber. Usually happens in winter.

diesel wont start

Also, if the engine was able to start, it will run intermittently. If the diesel does not start "hot", it is possible that several glow plugs have failed at once.


This element is controlled by a relay. Sometimes a breakdown of this element causes problems with starting the motor. How to check it? When starting the car, you should hear characteristic clicks from the spark plug relay. If not, the element is burned out and needs to be replaced. The candles themselves are in perfect working order.

Fuel system

As we said earlier, its device is significantly different from its gasoline counterparts. In 60 percent of cases (including on Ford cars), a diesel engine will not start due to problems in the fuel system. The first thing that could be is a clogged injector. This is due to poor quality fuel. their owncannot be cleaned - only in a specialized service.


For what other reasons does a diesel engine not start? Of course, these are filters. You need to check their condition.

There are two levels of cleaning in the diesel engine fuel system - coarse and fine.

diesel won't start when cold

The latter should be given special attention. The paper cavity of the filter, through which the fuel passes to the nozzles, is capable of retaining particles up to 10 microns in size. The resource of this element is 8-10 thousand kilometers. If you do not follow this regulation, the filter will simply become clogged. As a result, fuel will not enter the combustion chamber, although the pump produces the desired pressure. You can determine this by the nature of the movement of the car. If dips in dynamics are observed, this means that the fuel is supplied with a delay. And it is the filter clogged with dirt that delays it.It is worth mentioning about the air elements.

ford diesel wont start

Such filters also require replacement. According to the regulations, their service life is 10 thousand kilometers.

diesel starts badly

They are stored in a plastic case, you can replace them with your own hands by sliding the mounting brackets and removing the cover. The photo above shows what a dirty air filter looks like. As a result, the diesel will not start. Oxygen supply stops or decreases to the minimum level. The engine does not get enough air - it chokes on fuel.

Dark smoke

If the engine is difficult to start, and black comes out of the exhaust pipesmoke, this indicates the incorrect operation of the injectors, namely their spraying of fuel. It is produced in excess, which is why part of the fuel does not have time to burn out and flies, as they say, “down the pipe.”


There are two mechanisms in the system. These are high pressure fuel pump and high pressure fuel pump. Often the first element fails, since its device 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 "sneezes" (as if the car does not have enough fuel). It should be noted that a belt is connected to the injection pump. It may break or fall 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. Often this happens with a short circuit. Experienced motorists are advised to always carry a set of spare fuses in the glove compartment.

Fuel and winter

Diesel is especially often difficult to start 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 "solar oil" simply freezes. At low temperatures, it crystallizes and turns into paraffin, which clogs in fuel lines and filters.

diesel starts and stops

Further movement with such a filter as in the photo above is simply impossible. Some vehicles have filter heating installed. But it saves only at startup. After a couple of seconds, the car turns off again. It is very difficult to heat up the entire tank with frozen fuel. NotAll vehicles have a pre-heater. What is the difference between summer and winter fuel? In the presence of additives that reduce the waxing threshold at low temperatures. To prevent the problem from taking you by surprise, before the onset of cold weather, purchase an additive in diesel fuel. Experienced motorists recommend not to leave the car in the parking lot with a half-empty tank. During the night, the liquid condenses and water forms on the walls. It also does not have the best effect on starting the engine. In winter, try to keep the level above half. Especially since riding on an empty tank often kills the pump. This applies not only to diesel vehicles, but also to gasoline vehicles.


He has a problem with both petrol and diesel cars. A relay is also connected to it.

diesel does not start hot

And if the starter does not turn, listen for clicks, as is the case with the glow plug relay. Maybe it's a break in the circuit. Check battery charge. Of course, it wouldn'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 drop in level occurs in the event of a short to ground. Perhaps the contact has broken off and is “shorting away”.

Timing Belt

Why else won't the diesel engine start? 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 breakdown is accompanied bydeformation of intake and exhaust valves. They bend when the piston hits.

why diesel wont start

In order not to bring the car to such a state, check the condition of the belt. In the presence of tears and 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 warp one or more teeth. Manufacturers say that the circuit in the engine is designed to last the life of the engine. But after 200 thousand, it stretches - noises are heard during operation. With such symptoms, it is urgent to change it.


So, we found out why the diesel does not start. As you can see, there can be many reasons. But to avoid such a situation, change the filters in time and fill in high-quality fuel (in winter, be sure to use arctic fuel). If it is very cold, take the battery with you into the house. In severe frosts, it loses up to 30 percent of its charge overnight. This way you will provide the system with a good starting current, and the engine with clean fuel. And you won't have to worry about hard starting anymore.

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