Car Won't Start? Common Causes Explained

A car refusing to start or the engine simply stalling during driving is a real nuisance, although there is no immediate reason for panic. It is more than likely that a minor defect is causing the malfunction. Finding the cause, however, requires a thorough knowledge of a car’s operation. Read everything on what can cause the stalling of a car in this guide and how you can help yourself in such a case.

What Does a Car Need for Driving?

A car with a combustion engine needs six essential elements to enable propulsion. If even one of these elements fails, the entire engine can stall. Depending on which system is affected, the car might be very simply made functional again, or a lot of work could be involved for its repair.

The Six Essential Elements:

• Fuel: Petrol, diesel, or gas.
• Drive: Belts that tune the moving components.
• Energy: Electric ignition current for the operation of the starter.
• Air: For the preparation of the air-fuel mix.
• Oil: For the lubrication of the moving elements.
• Water: For cooling the engine.

Car Doesn’t Start – Fuel Supply Failure

If a car doesn’t start or stalls, the first suspicion often falls on the fuel supply. If the car rattles but refuses to start, it's possible the fuel tank is empty. If the fuel indicator indicates the presence of fuel, the tank float might be stuck. This can sometimes be checked by adding a small amount of petrol to the tank and attempting to start again. This requires a bit of patience, as a completely empty fuel system must be allowed to vent itself first.

If the tank empties unusually fast, be sure to check for a petrol smell. Possibly, the fuel hose is leaking. Alternatively, the fuel pump might be malfunctioning. A faulty fuel pump can prevent fuel from reaching the engine, leading to a no-start condition.

Repeatedly Refuses Operation – Belt Drive Failure

Belt drive malfunctions can often have severe consequences. If the timing belt or chain has ruptured, the engine will stall and will not start again. Often, the engine has sustained considerable damage in this case, and an expensive repair is necessary. This can be checked by removing the cover of the belt or chain. If the drive components have come off, the cause is found. Repair will involve more than just belt replacement; in this scenario, the engine may need to be completely disassembled.

Common Belt Issues:

• Timing Belt/Chain: Crucial for synchronising engine components. A break here is catastrophic.
• Serpentine Belt: Powers accessories like the alternator and water pump. While less critical for starting, a broken serpentine belt can lead to overheating or a dead battery.

Ignition Doesn’t Start – Electricity Supply Failure

The most common cause for an engine failing to start is a failure in the electricity supply. The electric current is generated in the generator (alternator), stored in the battery, and led to the spark plugs in the engine by way of the ignition coil and the ignition distributor. Current always runs in a circuit; if the circuit is interrupted, there is no supply. The return current to the generator always goes by way of the bodywork. Therefore, both the generator and the battery need to be grounded, which means they must be connected to the bodywork by cables.

Key Electrical Components and Issues:

• Battery: The heart of the electrical system. A dead or weak battery is a primary suspect. Corrosion on the battery terminals or cables can impede the flow of electricity. The solution is often simple: remove the earth cable, sand it clean, and grease it with pole grease. Reattach the cable, and the problem may be solved.
• Alternator (Generator): If the alternator fails, the battery will not be charged. This is usually indicated by a permanent warning light on the dashboard. If this is ignored for too long, the ignition coil will eventually no longer receive ignition current. In that case, the battery needs charging first, and then the alternator must be checked. Generally, alternator defects are minor: either the drive belt is defective or the carbon brushes are worn. Both can be simply repaired at little cost.
• Ignition Coil: Transforms the 12 Volt current supplied by the battery into the high voltage (10,000+ Volts) needed for the spark plugs. A cable runs between the ignition coil and the distributor (in older cars) or directly to the spark plugs (in newer cars). In older cars, the distributor cable might have become disengaged. This is a very evident reason for a car refusing to start: simply plugging in the cable can enable the car to drive on. If the cable is in its place but doesn't generate sparks, or if the sparks are weak, the insulation might be damaged. This could be the result of a rodent’s bite. An emergency measure is wrapping the ignition cable with insulation tape.
• Spark Plugs and Ignition Leads: Worn-out spark plugs or faulty ignition leads can prevent a strong spark from igniting the fuel-air mixture.
• Starter Motor: A problem connected to the electricity supply can be the starter motor. This element consists of an electric motor and an electro-magnetically driven relay. Over time, the starter can wear down, or its connecting contacts might be corroded. A starter failure often makes itself heard by a humming sound. The electromagnet cannot fully disengage the starter drive while the electric motor is still running. With a bit of luck, this defect can be repaired; very often, replacement is the only option.

Car No Longer Starts Suddenly – Air Supply Failure

A car stalling due to an air supply failure rarely occurs, although it is theoretically possible. If a foreign object lands in the inlet tract or if an air filter is severely clogged, the engine receives insufficient oxygen for the air-fuel mix. This error is often announced by increased fuel consumption and a hot engine. Replacing the air filter and checking the inlet tract generally should make the car work again.

Car Doesn’t Start – Oil and Water Supply Failure

If the coolant or oil supply fails, serious engine damage could occur. The dreaded piston seizure is a result of a shortage of one of these two components. If this occurs, the car cannot be repaired with household remedies, and a thorough engine overhaul is required. Therefore, if engine control lights or warning lights for the coolant or oil pressure illuminate, immediately switch off the engine!

Critical Fluid Levels:

• Engine Oil: Essential for lubrication and cooling. Low oil pressure can lead to catastrophic engine failure.
• Coolant: Prevents the engine from overheating. A lack of coolant can cause the engine to overheat rapidly and seize.

What to Do If Your Engine Goes on Strike: A Troubleshooting Checklist

The following checklist can help you narrow down the causes of a stalling car:

Scenario 1: Car Stalled During Driving

• Possible Causes: No more petrol, ignition contacts defective, engine damage.

Scenario 2: Car Now Refuses to Start

• If the Starter Rattles: This usually indicates the belt drive is okay, there’s no fuel, or an ignition cable has become loose.
  • Check the fuel indicator.
  • If the tank is empty: fill it up.
  • If the indicator shows sufficient fuel: check ignition cables.
  • If an ignition cable has become loose, plug it back in securely.
  • If the ignition cable generates weak sparks when starting: Insulation is likely damaged. Wrap the cable with insulation tape as a temporary fix and replace it as soon as possible.
  • If the ignition cable is okay, add more fuel (just in case the indicator is faulty).
  • If the car still doesn’t start despite sufficient fuel: try push-starting the car (for manual transmissions).
  • If the car allows push-starting: check the alternator, earth cable, and ignition coil.
  • If the car does not allow push-starting: check ignition contacts (and potentially the starter motor).
• If the Starter Makes No Sound: This could indicate engine damage (engine is blocked) or a completely dead battery/faulty starter.

Scenario 3: Car Doesn’t Start in Cold Conditions

• If the car is totally dead (no lights or very weak lights): The battery is totally empty. A jump-start is required. (In this case, the battery often needs replacement).
• If the starter rattles during a jump-start, but the car refuses to start: Check fuel supply, air supply, and ignition cables.
• If the starter makes no sound during a jump-start: The starter is defective, or there is engine damage. Try to tow-start the car. (Attention: Diesel cars cannot typically be tow-started in cold conditions due to the lack of spark plugs).
• If the car doesn’t start despite tow-starting and the wheels block: This strongly suggests engine damage, and immediate repair is necessary.

Final Checks:

If all these measures have no effect, there is one more possibility before going to a garage: check all fuses, especially in diesel cars. The glow plug fuses can be defective. If everything is alright here too, the car should definitely be checked by a qualified mechanic.

Common Causes Summary:

Disclaimer: This guide provides general information. Always consult a qualified mechanic for accurate diagnosis and repair of your vehicle.

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