If your car has trouble starting but runs fine, there are many possible causes. This guide will go over some of them, explaining why your engine is finding it so difficult and what you can do to fix it.
In addition to mechanical wear and failure, a few other factors can make a difference, such as weather, temperature, fuel type and condition, and the age of the vehicle.
Check for lights on your dash as well. These can be very informative.
Although you’ll find some different ideas on this page, there’s no substitute for an in-person diagnosis from a qualified mechanic.
Specialized equipment such as battery testers and OBD II code readers (both of which you can obtain yourself if you wish) are invaluable here.
Electric system
If your car has trouble starting but runs fine, it is most likely due to a minor fault in the electrical system.
There are many other possibilities that you should also consider, of course. Still, an electrical inspection will likely resolve this issue for most drivers.
Remember, it’s not necessarily about the battery. The electrical system also comprises a few other prominent players: the starter, the key, the alternator, and miles of wiring.
Starting motor
A starter motor (starter motor)
The starter motor (or related problems) will be the cause in many cases. This is especially true if you find that the car is having a hard time starting, but the battery is fine.
The starter motor is connected to a circuit that includes the ignition key and the battery. An electrical current is sent to the motor when you turn the key.
It then pushes its pinion gear into mesh with the engine’s flywheel. Electricity drives this little pinion with high torque, starting the engine and giving it the boost it needs to start. Then it will run under its own power.
If the starter motor has developed a wear-related failure and is not working well, it will be difficult to start the engine. As a result, the car has a hard time starting.
Check the condition of the starter with a specialized battery tester, saving you the need to remove it from the car. If you find it to be in bad shape, you’ll need to rebuild it or, more likely, replace it.
battery or alternator
The battery and alternator work together to produce and store electrical energy. The alternator is driven by the serpentine belt attached to the crankshaft and charges the battery as the engine runs. In turn, the battery distributes power to the engine and electrical components inside the car.
When you turn the key in the ignition, all the power comes from the battery. The engine isn’t running yet, so the alternator won’t do anything. If the battery is having trouble holding a charge, it won’t be able to send as much power to the starter as it should.
This could be due to a couple of things. If the battery has a crack, leak, or other damage, it will not be able to hold a charge. Likewise, if the alternator isn’t running at its normal speed due to an internal failure, a loose pulley, or a loose belt, it won’t recharge the battery fast enough.
One last important factor is the duration of your trips. A battery can take half an hour of highway driving to fully recharge.
If you do a lot of shorter, stop-and-go city trips, your battery will deplete much faster. Take your car for a quick hour-long drive up and down the highway to see if the problem persists.
Again, a battery tester is the best solution here. It will reveal any problems with the battery or alternator. These can be replaced if necessary.
bad wiring
Bad wiring could be the reason why your car is hard to start but runs fine. There are miles of wiring looms inside a modern vehicle, so start with the ignition wiring and connections to the starter.
The starter motor circuit is activated when you turn the key to START. If there’s a problem here, it could be sending less current than it should.
Unless you are an electrical expert yourself and have access to your own equipment (multimeters and such), this may require professional diagnosis. Take your car to an automotive electrician and start from there. Unfortunately, this can be quite expensive, but there’s no way around it.
It is better to rule out other possible causes before investing in electrical diagnostics.
Almost any engine component, if it malfunctions, could cause this problem. In addition to those listed below, consider checking the ignition timing, camshaft, timing belt, distributor cap, and all filters (air, oil, and fuel).
Plugs
Over time, the spark plug gap can be enlarged. As such, they require more electrical energy for a spark to fill said gap.
You may notice this when starting because the engine may need to rev up more than usual before it gets going. However, once the alternator is running the engine at higher revs, spark plug gap may be much less of an issue.
Fixing this requires reopening the spark plugs. Although you will need some depth gauges, it is a relatively simple process. Alternatively, you can swap out all the spark plugs with new ones (something that needs to be done quite often anyway).
Carbon can also build up on old spark plugs, causing a similar problem. You will notice a black, soot-like sand covering the pieces. They will need to be replaced.
The job of the fuel injectors is to inject the fuel (big surprise!) into the engine. They are electronically controlled and specifically designed to put a certain amount of gasoline or diesel into the combustion chamber.
If the fuel injector does not insert enough (or too much) fuel, the resulting air/fuel mixture will not burn properly. This will make the engine difficult to start.
The problem is likely to persist while the car is running. However, if it is just a minor problem, you may not notice it as much as during the engine cranking process.
Defective injectors will need to be replaced. You can use a multimeter to check if each part is working. An OBD II code reader can also give you your answer. You just have to expect one or two to fail at any given time.
Anything else to stop working would be very unusual and probably indicates a deeper electrical issue.
Climate
Believe it or not, the weather can significantly affect your vehicle, especially during starting, particularly cold weather. Cars don’t like negative temperatures, cold winds, snow, ice, or fog/freezing rain.
When it’s winter, all the fluids in a car are thicker or freeze completely. Both fuel and motor oil struggle to flow until they get hot. Water in batteries can freeze, leading to low (or no!) power.
In freezing climates, such as the northern states, Canada, Scandinavia or Russia, cars may regularly need a boost from a battery charger to get them going in the morning.
However, once the car is running it should warm up in ten to fifteen minutes, and everything should run as usual from there.
So is it a cold day? Or maybe a mild day with a cool gust from the north? Even an exceptionally wet day? Any of these could be why your car is hard to start when cold but then runs fine.
The best option is to park your car in a shelter like a garage or even a makeshift tent. It’s not a perfect solution, but it could make a difference.
Beware of carbon monoxide exhaust when starting the vehicle. These can be deadly if you don’t open the doors before starting the car.
Space heaters are also an option, but not recommended. They are known to cause fires.
concluding thoughts
When an engine has trouble starting but seems fine once it’s running, it needs to be diagnosed as soon as possible. Although it may seem like an inconvenience, it will be a real hassle if you drive 20 miles to work and then get stuck there when the car won’t start.
You can check, eliminate, or confirm many potential causes yourself using DIY tools. Start by considering the impact of weather, then check the ignition, electrical systems, and engine components.
If you can’t find the source of the problem, take your car to a trusted local mechanic. Getting it fixed as quickly as possible is likely to save you a lot more in future costs.
