Why won't my car start?

A starting problem often happens at the worst possible time: before going to work, just as you are about to leave or when the vehicle is parked far from a garage. The first reaction is often to suspect the battery, but simply stating that “my car won't start” is not enough to identify the cause.

The starting circuit, electrical supply, key, immobiliser, fuel, ignition, injection system, various sensors or a mechanical problem can produce similar symptoms. The first step is therefore to describe exactly what happens when you turn the key or press the Start button.

What exactly does the car do when you try to start it?

Several behaviours may seem similar to the driver. Grouping them into a simple sequence helps guide the diagnosis because each one corresponds to different causes.

It is also useful to indicate whether the problem appeared suddenly or gradually, after a repair, refuelling, a long period without use, a dashboard message or previous starting difficulties.

Why does the car do absolutely nothing?

If no dashboard lights come on and no sound is heard, the battery and its connections are among the first things to check. A loose terminal, a cable, an earth connection, a main fuse or the general power supply can also interrupt the circuit.

If the electrical equipment works but the starter motor does not respond, the investigation may also involve the starting command, the starter motor, a relay, the ignition switch, key recognition or a safety condition that has not been met by the vehicle.

Automatic transmission, clutch and start authorisation

An automatic transmission must generally be in P or N. On some vehicles with a manual transmission, the clutch pedal must be fully depressed. Depending on the model, an open door, an undetected brake input, an unrecognised key or an incorrectly detected selector position can also prevent the starting command.

Why does the car click or crank very slowly?

Slow cranking, repeated clicking or a dashboard that goes dark when you try to start often indicate insufficient voltage. The battery may be discharged, ageing or unable to supply the required current.

However, this symptom may also be caused by a corroded or loose terminal, a cable, a poor earth connection, the relay or the starter motor itself. A single click is therefore not enough to automatically condemn the battery or starter motor.

A jump start may get the vehicle running again if the battery is discharged, but it does not reveal why it lost its charge. A battery that no longer holds its charge, a defective alternator or an electrical drain while parked can cause the vehicle to become immobilised again.

Why does the starter motor turn without the engine starting?

When the starter motor cranks the engine at an apparently normal speed, the battery is less likely to be the only cause. The engine must receive fuel, air, the correct injection command and, on a petrol engine, correctly timed ignition.

Depending on the vehicle and symptoms, the investigation may include:

• fuel supply and pressure;
• ignition on a petrol engine;
• injection and the signals required by the control unit;
• an engine position or speed sensor;
• the key or immobiliser system;
• engine timing, compression or another mechanical cause;
• an electrical or electronic fault preventing start authorisation.

A diagnostic scanner can provide fault codes and useful values, but a code does not automatically identify the part that needs replacing. The conditions under which the fault appeared, power supplies, signals and the actual operation of the relevant system must be checked.

Why does the engine start and then stop?

An engine that starts and then stalls immediately presents a different situation. The immobiliser may interrupt operation if the key is not recognised, but a fuel, pressure, air-intake, sensor or engine-management problem can also cause the engine to stop.

Check whether a key symbol, immobiliser message, unusual warning light or alert appears. If a second original key is available, trying it may provide a useful indication, provided the vehicle's normal procedure is followed.

If the engine stalls with a mechanical noise, severe vibration, smoke or an unusual smell, do not try again. The vehicle should be inspected before any further attempt.

What can you safely check yourself?

Without dismantling anything or bypassing a safety system, you can check:

• whether the dashboard lights and headlights illuminate normally;
• the sound produced: silence, one click, rapid clicking or normal cranking;
• the messages and symbols displayed on the dashboard;
• whether the automatic transmission is in P or N;
• whether the clutch or brake pedal is fully depressed, depending on the vehicle;
• whether a second original key is available;
• the fuel level, without relying only on an old estimate;
• symptoms that appeared before the fault and any recent work;
• the visual condition of the battery and connections, without touching a damaged battery.

Briefly filming the dashboard and recording the starting sound can help the technician understand the situation before the intervention. Also prepare the vehicle registration document and the vehicle's exact address.

When should you stop trying to start the car?

Repeated attempts can completely discharge the battery, overheat the starter motor and complicate the diagnosis. If the vehicle does not start after several normal attempts, it is better to stop and observe the symptoms.

Stop trying immediately if you notice:

• smoke or a burning smell;
• a strong smell of fuel;
• a significant or unusual mechanical noise;
• a visible leak beneath the vehicle;
• a hot, deformed or damaged battery;
• a message instructing you to stop the vehicle;
• any doubt about the engine timing or mechanical integrity.

In these situations, you should not force the vehicle to start or drive it. Appropriate diagnostics, breakdown assistance or transport should be arranged.

Why diagnose the problem before replacing a part?

A new battery will not solve a starter-motor problem. A new starter motor will not correct a poor earth connection. A fuel pump should not be replaced simply because the engine cranks without starting.

Depending on the situation, a methodical investigation may include:

• precise confirmation of the symptom;
• inspection of the battery, terminals, cables and earth connections;
• testing the battery capacity and charging system;
• checking the starter circuit and command;
• reading fault codes and analysing useful values;
• checking start authorisations and the immobiliser;
• the necessary fuel-supply, ignition, injection or mechanical checks.

The aim is not merely to get the vehicle started once, but to identify the cause in order to prevent another breakdown and unnecessary replacements.

What can Depamec do if your car is immobilised in Geneva?

Depending on the vehicle, situation and location, Depamec can carry out an initial diagnosis directly where the car is located. The intervention may include checking the electrical supply, battery, starting system, charging system and available electronic information.

If the cause can be addressed on site and the conditions allow it, the appropriate solution can be proposed. If the fault requires workshop equipment, a more substantial repair or the vehicle cannot be driven safely, suitable transport or assistance should be arranged.

To prepare your request, provide the make, model, registration number, exact address, the behaviour observed when starting, any messages displayed and any symptoms that appeared before the vehicle became immobilised.

Learn more about diagnosing your car

How can you tell if your car battery has failed? → Engine warning light on: what should you do? → Your car is making a noise: is it serious? → Maintain your car without losing half a day →

Frequently asked questions when a car will not start

Why won't my car start even though the dashboard lights come on?

Dashboard lights require much less current than the starter motor. They can therefore illuminate even when the battery is too weak to start the engine, although the starter motor, cables, immobiliser or other systems may also be responsible.

Why does my car only make a clicking sound?

A clicking sound may be caused by an insufficiently charged battery, a poor connection, a defective earth connection, a relay or the starter motor. The noise alone cannot identify the component responsible.

The starter motor turns, but the engine will not start: why?

When the starter motor cranks the engine correctly, the investigation may involve the fuel supply, ignition, injection, a sensor, the immobiliser, engine timing, compression or electronic management.

Is the battery necessarily responsible when the car will not start?

No. The battery is a common cause, but the starter motor, alternator, electrical connections, key, immobiliser, fuel supply and other systems can also prevent the engine from starting.

Should I continue trying to start the car?

It is better to stop after several unsuccessful attempts, particularly if there is smoke, an unusual smell, a leak, a mechanical noise or overheating. Repeated attempts can discharge the battery and place unnecessary strain on the starter motor.

Can Depamec diagnose an immobilised car in Geneva?

Depending on the vehicle, situation and location, Depamec can carry out an initial on-site diagnosis to identify the probable cause of the problem and determine the required intervention or transport.