One thing is certain: If the car does not start, it is guaranteed to be at the wrong moment: You have to cancel an appointment or you arrive far too late using alternative means of transport.
Maybe you call the mechanic or rummage in the depths of the trunk for the jump-start cable that was there last year. In this article, we’ll explain why a car won’t start and how you can tell where the problem is.
Is the battery empty?
If the battery is empty, the interior lighting remains dark and the radio cannot be switched on. Reasons for a dead battery can be:
- The battery is old and has a voltage below 12 V even after sufficient charging time. Then it has to be renewed. The voltage can easily be checked with a commercially available multimeter. Get help getting started and drive straight to the workshop to change the batteries. In some modern vehicles, the new battery has to be taught in, otherwise an error message may appear.
- You haven’t moved the car for a few weeks or months and the battery has drained over time. With a largely discharged battery with low voltage, the starter turns weakly. Here, too, you need help getting started.
- You forgot to switch off a power consumer when parking, for example the interior lighting.
- The electrical lines are damaged or have no contact (marten bites, corrosion). The jump start will not help you here. You can disconnect the battery and sand the contacts clean and smear them with pole grease. You remove the negative cable first and connect it again last. If that doesn’t work, the car has to be towed to the workshop.
- If the alternator is defective , it will no longer charge the battery
If you have got jump start, an intact battery should be sufficiently charged after several kilometers. Old batteries need a little longer for this. If the alternator is broken, the battery is not charged; instead, all electrical consumers run on the remaining voltage of the battery and will gradually fail in a short time. Whether you can still come to the workshop with it is a matter of luck. You can recognize a fault in the charging process by the charging indicator light in the cockpit. This lights up for a few seconds when starting and should then normally go out.
How to jump start a battery
- Check the operating instructions to see whether there is anything specific to consider when it comes to jump-starting your vehicle.
- The jump start cable must have a sufficient cross-section and meet the ISO 6722 (DIN 72553) standard.
- Ignition off in both vehicles.
- Red positive cable: Connect to the positive terminal only when the battery is full and only then to the positive terminal when the battery is empty. Make sure that there is good contact when connecting.
- Black negative cable: Only when the battery is full at the negative pole and then to the earth point of the other car with the empty battery. The ground point should be specified in the operating manual, otherwise you use a bare metal point on the engine block.
- The vehicle is now started with the intact battery. Let it run a little so that the empty battery is charged a little.
- The broken-down car is now started. If it does not start after several attempts, then there is very likely another problem and the car will have to be towed to the workshop.
- Finally, remove the starter cables in the correct order: Black negative cable – first on the full battery, then on the empty one. Then the positive cable – also first from the full battery.
- To properly recharge the battery, we recommend a lap on the motorway or country road.
Disconnect and reconnect the cables in exactly the right order. You handle electricity, which in the worst case can damage the sensitive on-board electronics.
The car won’t start in winter or when it’s cold
Low temperatures put a strain on the battery’s capacity.
If you often only drive very short distances, the alternator can no longer fully charge the battery, especially in winter. With a starter cable in the trunk, you’re on the safe side. Because only very few drivers will turn you away if you ask for help in a friendly manner and have the necessary equipment directly at hand.
After about ten minutes of driving, the alternator should have balanced the starting process again. If you have frequent problems with the battery at startup, we recommend replacing the battery.
Diesel engines have their own problem in winter: at low temperatures, paraffin flakes form in the fuel, which can clog the fuel system and the fuel filter. Then the vehicle will no longer start. That is why the filling stations in Germany sell the so-called winter diesel during the cold months. Special additives are added to this for better cold resistance. On extremely cold days, however, it is advisable to add an additive when refueling so that your vehicle starts reliably in the morning.
Spark plugs, fuel pump or ignition lock defective
If the ignition lock or the ignition electronics are defective, the interior lighting and radio work as usual. When the key is turned, the start button is pressed or the chip card is defective, there is no reaction from the engine compartment.
If you hear the usual noises of the starter during the ignition process, then the spark plugs or the fuel pump are possible sources of error. If these parts are broken, the engine will try to start. However, there is no combustion because the fuel pump is not pumping fuel into the combustion chamber or there is no ignition spark for the explosion.
The vehicle has to go to the workshop. Because you can only repair the defect yourself with sufficient specialist knowledge and the right tools.
If the starter is defective, the battery will provide enough power for the start, but the starter will not start the engine. Various components of a starter can break. For example, the pinion may be worn, the magnetic switch may be stuck or the freewheel has a problem.
If the starter is broken, you can let the car roll to start the engine. If the magnetic switch hangs, in some cases it helps if a second person knocks on the magnetic switch with a hammer while you are operating the ignition.