1. A flat or dead battery
The most common cause by far. If you get nothing, no dashboard lights, no crank, or only a faint response, the battery is the first suspect. Batteries fail more in extreme heat, which Brisbane has plenty of, and they usually last a few years. See our battery replacement page.
Clue: no lights, no crank, or everything's dim.
2. A bad connection
Sometimes the battery is fine but the connections are corroded or loose. That can mimic a flat battery. It's worth a look, though testing confirms it.
Clue: intermittent starting, or it started after wiggling something.
3. A faulty starter motor
The starter motor cranks the engine. When it fails, you often get a single click when you turn the key, or nothing, while the dash lights stay strong. It can also fail intermittently.
Clue: a single click with no crank, but the lights work.
4. The alternator hasn't been charging
The alternator recharges the battery as you drive. If it's failed, the battery slowly goes flat and eventually won't start the car, even a brand-new battery. This is why replacing the battery alone sometimes doesn't fix a repeat no-start.
Clue: the battery keeps going flat, or the battery light was on before it died.
5. A fuel issue
If the engine cranks normally but won't fire, it may not be getting fuel. Causes range from an empty tank (it happens) to a fuel pump or filter problem.
Clue: cranks strongly but won't start.
6. Ignition or security fault
Modern cars have immobilisers and security systems that can stop the car starting if they don't recognise the key, or if there's a fault. An ignition switch problem can do the same.
Clue: everything powers up but there's no crank, or a security light is showing.
The right way to find it
The symptoms narrow it down, but the only way to be sure is to test. A mechanic checks the battery, connections, starter and charging system in order, so the actual cause gets fixed rather than the first likely guess. A jump start might get you going once, but if the battery or alternator has failed, it'll happen again.
If your car won't start, we come to you, test it properly, and fix the cause on the spot where we can. See our car won't start page.