A car that won't start is one of the most frustrating situations a driver can face — especially when you are in a hurry. The cause could be something simple that you can fix yourself in minutes, or it could be a serious mechanical failure that requires professional recovery. This guide covers the 10 most common reasons a car won't start, how to diagnose the problem, and what to do in each case.
A flat battery is by far the most common reason a car won't start. Signs include: the engine turns over slowly or not at all; the dashboard lights are dim or don't come on; you hear a clicking sound when you turn the key. A flat battery can be caused by leaving lights on, a faulty alternator, or simply old age (most car batteries last 3–5 years). Solution: try jump starting the car using jump leads and a running vehicle, or call for roadside assistance. If the battery is old, it may need replacing.
If you hear a single loud click (not rapid clicking) when you turn the key, the starter motor may have failed. The starter motor is the electric motor that cranks the engine to start it. A faulty starter motor cannot be fixed at the roadside — your vehicle will need to be recovered to a garage. Signs: single click when turning the key; engine does not turn over at all; battery is fully charged but car still won't start.
It sounds obvious, but running out of fuel is a surprisingly common reason for a car not starting. Modern fuel gauges can be inaccurate, and the 'empty' warning light may not come on until there is very little fuel left. Check your fuel gauge. If the tank is empty, you will need fuel delivered or to be recovered to a petrol station.
The alternator charges the battery while the engine is running. If the alternator fails, the battery will gradually drain and eventually the car will not start. Signs: battery warning light on the dashboard; dimming lights while driving; battery going flat repeatedly even after replacement. A faulty alternator requires a garage repair.
If you have been trying to start the car repeatedly without success, or if you have been cranking the engine for a long time, the engine may be flooded with fuel. Signs: strong smell of petrol; engine turns over but won't fire. Solution: leave the car for 10–15 minutes with the bonnet open to allow the excess fuel to evaporate, then try starting with the accelerator pressed to the floor (do not pump it). If this doesn't work, the car may need professional attention.
The ignition switch sends the signal to start the engine. If it fails, turning the key or pressing the start button will have no effect. Signs: nothing happens when you turn the key; no dashboard lights; steering lock not releasing. A faulty ignition switch requires a garage repair.
Modern cars have electronic immobilisers that prevent the engine from starting if the correct key is not detected. If the immobiliser is triggered (for example, by a flat key fob battery or a fault in the system), the car will not start. Signs: immobiliser warning light on the dashboard; engine turns over but won't fire; key fob not working. Try replacing the key fob battery. If the problem persists, the car may need to be taken to a dealer.
The fuel pump delivers fuel from the tank to the engine. If it fails, the engine will not receive fuel and will not start. Signs: engine cranks but won't fire; no fuel pressure; car starts intermittently. A faulty fuel pump requires a garage repair.
The timing belt (or timing chain) synchronises the engine's valves and pistons. If it snaps, the engine will stop immediately and will not restart. This is a serious mechanical failure that can cause significant engine damage. Signs: engine stops suddenly while driving; loud bang before engine stops; engine cranks but won't start. Do not attempt to start the engine if you suspect a timing belt failure — this can cause further damage. The car will need to be recovered to a garage.
In very cold weather, fuel lines can freeze (more common in diesel vehicles), door locks can freeze, and the engine oil can become too thick to allow easy starting. Solutions: for frozen fuel lines, park the car in a warm garage if possible; for frozen locks, use a de-icer spray; for cold-weather starting, ensure your battery is in good condition before winter and use the correct grade of engine oil for the temperature.
Car won't start and you need help? Black Eagle Recovery provides 24/7 roadside assistance and recovery across London and the South East. Call 0330 520 1620 — we'll get you moving again.
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