Important tips for troubleshooting a car that won’t start

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Image by Ryan Doka from Pixabay

Although cars have become a lot more reliable over the years thanks to fuel injection and modern technology, they can still fail from time to time. One of the biggest issues drivers still face is their car not starting, which can be dangerous if it conks out on the move and refuses to start again. This can be due to several reasons from something trivial like a bad battery to more complicated issues like a faulty ECU which can cost thousands to fix. So, let’s take a look at some of the reasons why your car won’t start and how to fix it in a jiffy.

Unlike older cars with carburetors which were relatively simple to fix, all modern models from the humble Honda Civic to the Dodge Charger use complicated fuel injection technology which is a lot harder to diagnose.

Before we start the diagnosis, make sure it’s not something as simple as running out of fuel. Once the fuel level is checked, the next step is to check the battery. If the battery cannot hold a charge, it may be because of a bad alternator. If you have a multimeter in hand, use it to check the voltage with the car off.

If it’s a fairly new battery, it should show 12.6 volts, indicating a full charge. If the voltage reading is 12 or below, the battery is faulty or at a low charge. If the charge is low, load test the battery at your local dealer and replace it to get your car running again. If you drive around with a bad battery, it can damage your alternator since it’s overworked.

A bad alternator can cause the car to conk out after installing a new battery. The ideal voltage reading when a car is running should be 13.7 to 14.7, indicating the battery is being charged.

If both your alternator and battery checks out, the next step is to plug in an OBD reader to check for fault codes. If some fault codes show up, try diagnosing and repairing them. Modern cars use several sensors to send the correct signals to the ECU and run the car. If some of these sensors become faulty, a check engine light will appear on the dashboard, and can sometimes cause the car to run rough or shut off on the move. If this happens, always get the car out of the road first and turn on your hazards to warn other motorists.

Sometimes, the car will start after cooling down a bit. This could be because of faulty sensors, more specifically, the crankshaft position sensor which can give the wrong position to the ECU, causing misfires and stalling the engine.

However, if the car still doesn’t start, let’s take a look at the four components that work together to start and run the car: spark, fuel, air, and compression.


In some cases, the fuel gauge can be faulty, and show irregular readings even when the tank is empty.

Once you have determined the fuel level, the next step is to check if the fuel is reaching the engine. As the car ages, the fuel pump and other components in the fueling system wear out and can stop working.

The first component to check is the fuel pump. When the ignition is turned to the “On” position, you’ll be able to hear the fuel pump priming. If the sound seems weak and slow, the fuel pump is on the way out. When the fuel pump fails, the engine won’t be able to start because of no fuel pressure.

If the pump is working, check for a clogged fuel filter. It is usually located on the fuel pump itself and filters the fuel before it enters the pump. Most cars also have a secondary fuel filter before it enters the fuel injectors. Check both the filters, and replace them if they’re clogged. Also, check the fuel lines for any leaks along with the fuel pressure at the rail. Weak fuel pressure can also indicate a failing fuel pump.

The fuel injectors can also fail because of impurities, causing a misfire or completely stalling the engine. If the fuel system checks out, it’s time to move on to the ignition system.


In gasoline engines, a spark plug is used to ignite the fuel mixture, starting the engine. The plugs are run by ignition coils that time the spark according to the engine cycle. If the spark plugs are not changed in time, they can fail. If the plugs are new and clean, the issues could be with the ignition coils or the ignition switch. Most cars will show fault codes, indicating which cylinder is misfiring, helping you pin down the faulty coils.

If the ignition switch fails because of worn-out circuits, it will fail to bridge the circuit and cause a no-start condition. This will usually occur with old and high mileage cars.

Another common reason for a no-start condition is a faulty starter motor. If the car fails to crank even with a good battery, check if the engine cranks over. If it doesn’t crank or you hear a clicking noise, the starter motor may be broken or weak. You can try cycling the key and checking the battery terminals for a proper connection. Also, try hitting the starter motor to get it dislodged. If all else fails, replacing the starter will solve the issue.


An engine needs both fuel and air for ignition. In some cases, the air passage can get blocked, leading to a rich mixture and the engine not starting in some cases. Checking for issues is relatively simple. Start by checking the air filter for any clogs along with all of the intake hoses and the throttle body.

If the car has been parked for a while, rodents may make nests in the filter housings, blocking air from passing through the intake.

If all else fails, the issue may be more severe like a failed ECU or engine. When engines get worn out, the compression is affected and eventually, it will fail to start because of very low compression. If the ECU fails, none of the systems will work, and we recommend taking the car to a professional mechanic for further diagnosis.