49.15. Indicate the method for determining the cause why the engine does not start when the starter is turning.
UAВкажіть метод визначення причини, з якої двигун не запускається, коли обертається стартер.
Question without image
This exam question from the Traffic Rules of Ukraine concerns the technical condition of the vehicle and road safety: if the starter turns the engine but it does not start, the driver should not continue trying “blindly,” but must determine the cause of the malfunction. This approach is directly related to the requirement of the traffic rules to check the technical condition before driving and to monitor it during operation, as a faulty vehicle creates risks on the road and may let you down in a critical situation.
In essence, this question tests the section on the driver's duties regarding the technical condition and compliance with technical operation requirements (specifically paragraphs 2.3 and 31.1 of the Traffic Rules). For the theoretical exam, it is important to understand the logic of diagnostics: when the starter turns but the engine does not “catch,” the cause is determined comprehensively, combining different methods. A visual inspection of the wiring and contacts helps quickly find breaks, oxidized terminals, bad grounds, or power supply issues. An error diagnostic scanner (OBD) is useful in modern cars, as it can show sensor failures, immobilizer or injection system faults. And a step-by-step check of the starting and engine operation systems (fuel, ignition or preheating in diesels, compression) allows you to methodically narrow down the causes and not miss mechanical malfunctions.
The practical significance of this topic is that “the starter turns but the engine does not start” almost always means a problem with one of the key starting conditions, so the correct strategy for the driver is not a single “magic” method, but a combination of available checks: from simple inspection and basic tests to computer diagnostics and sequential checking of components. That is why, within the framework of the traffic rules and the logic of exam preparation, the correct approach is considered to be the use of all the listed methods depending on the situation and the equipment of the vehicle.
Clause 2.3 (subclause “a”)
To ensure road safety, the driver is obliged: before departure, to check and ensure the technical serviceability and completeness of the vehicle, as well as the correct placement and securing of the load.
Brief application: if the engine does not start (even though the starter turns the crankshaft), the driver must check the technical condition of the vehicle before starting to drive; in practice, this means searching for the cause in key systems (fuel supply/ignition/mechanical serviceability), i.e., applying all the diagnostic methods listed within reasonable and safe control.
Clause 2.3 (subclause “b”)
To ensure road safety, the driver is obliged: to monitor the technical condition of the vehicle and not to be distracted from driving while on the road.
Brief application: if a malfunction appears during an attempt to start (an indication of a technical condition violation), the driver must determine the cause and eliminate it/take measures, rather than trying to continue operation without diagnostics.
Clause 31.1
The technical condition of vehicles and their equipment must comply with the requirements of standards related to road safety and environmental protection, as well as the rules of technical operation and the instructions of manufacturers.
Brief application: The Traffic Rules do not establish a “single” method for determining the cause of a failure to start, but directly link technical serviceability to the requirements of standards and manufacturer instructions; therefore, comprehensive diagnostics are used to determine the cause (checking fuel supply, presence of spark/operation of the ignition system, compression, etc.), that is, all the actions listed in the options may be correct as a method for determining the cause.
Thus, the correct answer is “All of the above options,” given that according to the Traffic Rules, the driver is obliged to ensure and control the technical serviceability of the vehicle (clause 2.3) in accordance with the requirements of technical operation and manufacturer instructions (clause 31.1), and the cause of failure to start when the starter turns is determined precisely by a comprehensive check of possible system failures.
When the starter turns the crankshaft but the engine does not start, it means that mechanical rotation is occurring, but the conditions for starting are not met. To determine the cause, a step-by-step check of the main components without which the engine will not run is performed: fuel supply, ignition (or preheating in a diesel), and compression.
First, it is advisable to make sure that the starting system is working correctly. If the starter turns unevenly, with noticeable slowing or "sagging" of revolutions, the cause may be a weak battery, poor contacts, or malfunctions in the power circuits. But if the starter turns the engine steadily and there is no "catching," proceed to check the systems that ensure starting.
Next, check the ignition (for a gasoline engine) or the system that assists cold starting in a diesel. For a gasoline engine, the logic is simple: if there is no spark at the plugs, the fuel-air mixture will not ignite, and the engine will not start, even if the starter works properly. Therefore, checking for spark and related elements (plugs, ignition coil/module, high-voltage wires, sensor signals) is one of the basic methods for finding the cause. In a diesel, it is equally important to assess the operation of the glow plugs and their control, because without proper preheating, starting may not occur.
In parallel or as the next step, check the fuel supply. If fuel does not reach in the required amount or at the required pressure, the engine will also not start, even though the starter is turning the shaft. In practice, attention is paid to the operation of the fuel pump, the condition of fuses and relays, filter passability, the presence of pressure in the fuel line, and for diesels, also to possible air entry into the system and the serviceability of supply units. A typical sign of a fuel problem: after starting attempts, the plugs remain dry or, conversely, there is flooding and the engine is "overfilled."
If neither the ignition (or preheating in a diesel) nor the fuel supply raises suspicion, then check the compression and the mechanical condition of the engine. With low compression, the mixture is not compressed properly, and ignition becomes impossible. This happens, in particular, after overheating, problems with the valve timing mechanism, or wear of the cylinder-piston group. In such cases, compression measurement is necessary to confirm or rule out a mechanical cause of starting failure.
It is also worth remembering that in modern cars, the cause may be electronic locks or sensor failures, and then computer diagnostics help. But in principle, the method for determining the cause remains the same: all key starting conditions are checked sequentially, because failure of any of them will lead to the situation "the starter turns but the engine does not start."
Therefore, the correct answer is "All of the above options," since the cause of non-starting when the starter is turning is determined comprehensively, step by step checking the ignition (or preheating in a diesel), fuel supply, and compression, as well as the basic conditions for the operation of the starting system.