CAR WON'T START-10 MOST COMMON REASONS -

Car won’t start? Well, you’ve just encountered one of the most common car problems that can happen.

Especially if you drive an older, used, or high mileage car, you’re bound to get struck by this mishap.

When this does happen, this article will hopefully help you solve your problem.

You can read what are the most common reasons why the car won’t start as well as a list of symptoms at the end of the article.

Whether you decide to do a DIY job or visit a mechanic, this article should give you a good idea of what the problem may be or how to solve it.

CAR WON’T START-KNOW HOW TO EXPLAIN THE PROBLEM

Whether you decide to do a DIY job or visit a mechanic, having some basic knowledge of this problem and knowing how to explain it comes in very handy.

Basic knowledge

From the dawn of the combustion engine, these elements are needed to start the engine:

Air
Fuel
Spark (for petrol engines) or heating up the engine cylinder (with diesel engines)

Strong turnover of the engine provided by the car battery and starter.

Weak supply or lack of any of these means the car won’t start.

Have in mind that good engine condition (read engine compression) is a key factor. If the engine is on its last legs, you can have all of these elements in place and still, the car won’t start.

Explanation

When drivers say the car won’t start, it doesn’t explain the problem properly. On the contrary, it usually even causes more confusion.

You see, there are basically two types of this problem:

the car will crank but won’t start
the car will not crank at all

This division is where proper diagnostics of the problem starts. Even if you visit a mechanic, he/she will probably ask you this question first.

Pay attention to this when the problem occurs as it will be a big help in problem troubleshooting.

1. FLAT OR WEAK CAR BATTERY, LOSE OR BAD BATTERY CONNECTIONS-PERHAPS THE MOST COMMON REASON WHY THE CAR WON’T START

Car batteries have the purpose of supplying electrical power to the car while at standstill.

It gives power to the electric installation and appliances but most important for this matter, power to the car starter.

Car batteries have their own life-span. They mostly last for a couple of years (quality ones at least five years).

Won’t go into details, but due to a chemical process inside the battery, over time the cells inside get clogged and the battery is unable to produce electricity.

When you get a dead or weak car battery, you have two possibilities:

Replacing the car battery with a new one

This is the best solution if the battery has been on the car for some time or has been subdued to frequent maximum discharging (leaving the lights on, a lot of cranking, etc).

When buying a new one, make sure to buy the same one in terms of voltage, amperage, and battery terminal position (is plus or minus left or right, is it in the upper or lower corner of the car battery).

If you decide to replace the car battery on your own, click here to read a separate article on this topic.

You can also watch a video tutorial on this topic on our YouTube channel.

Recharging the car battery

This is only an option with car batteries that allow maintenance (battery cell lids can be opened).

To clarify, non-maintenance (read sealed batteries) can also be charged. But this is more dangerous as fumes produced during recharging have no outlet. This can cause a buildup of flammable gases inside the battery which is very dangerous.

If you decide to recharge the battery on your own, click here for a detailed procedure written in a separate article.

Recharging is OK if the car battery hasn’t been damaged (in terms of maximum discharge). If so, chances are that the car battery won’t be properly revived through recharging which can lead to sudden loss or weak power from the battery.

Recharging the battery is only good in terms of expense. For a small amount of house electricity and some distilled water (for refilling the battery electrolyte), you can finish the job.

But as mentioned, it can either serve for years to come or go flat at a moment’s notice, especially in winter conditions.

Do what you find fit. From my own experience, replacing the car battery is the real deal.

Make sure that the battery connections are clean and tightened

When talking about car battery problems, it must be mentioned that both the battery terminals and clamps must be squeaky clean and tight.

Even if you replace a new battery but the contact is bad, the car won’t start.

Check the terminals and clamps from time to time and give them a clean-up (sandpaper, file, cleaning substances, or else).

Especially do this if you see a green/white powder substance building up on the battery terminals.

Also, check that the clamps are properly tightened.

2. FAULTY CAR STARTER-WITHOUT A GOOD TURNOVER THE CAR WON’T START

A car starter is a device that cranks the engine until combustion starts.

For a better picture of how the starter works, click here to read a great explanation on Wikipedia.

It’s essentially an electric motor bolted to the engine which engages the flywheel and begins the engine turnover.

As with all electric motors (especially DC motors), overtime and due to various conditions (mostly material fatigue but also excessive cranking), the starter will start to malfunction.

The car starter has a service interval of its own and if properly maintained shouldn’t cause you problems.

But if it does happen, you have basically two possibilities:

Replacement

Starter motors are sold separately in every better car parts shop.

The replacement procedure is not that complicated (in short: disconnect, unbolt, remove old, insert new, bolt back up and re-connect) but highly depends on the car model in terms of accessibility.

With today’s cars and their crammed engine bays, this repair can be a pain.

If you visit a mechanic, prepare your wallet for a raid. Usually, this repair is pretty pricey in terms of parts and labor.

If you want to DIY the job, I wouldn’t advise unless you have at least minimal experience with car repairs.

Repairing the car starter

Repairing the car starter is also a common solution as the build allows it to be pulled apart and repaired.

Spare starter parts are sold separately in every better car parts shop (solenoids, starter gears, brushes, rotors, or else).

This option is good if you have experience with these repairs as it will save a good deal of money and time. The winning combination is doing the whole procedure on your own (taking off, fixing, and returning). Although for this, you must have some serious experience.

Some additional advice on car starter problems: weigh the cost of a new car starter versus repairing the old one. New is new and will always be better than repaired.

Also, take the whole procedure into consideration. Sometimes due to lack of skill or complicated procedure, it is more cost-time effective to let a professional do the job.

3. FAULTY ALTERNATOR ON A CAR

Alternators are small generators of electricity bolted to the car engine.

Once the car battery serves its purpose of giving electricity in the beginning, the alternator takes over that role when the car is started.

It provides electricity for all of the car systems and recharges the car battery at the same time.

If you have the time, click here for a great explanation of how the alternator actually works on Wikipedia.

Like car starters, alternators have a maintenance interval of their own. Despite the fact that they are very durable, if not properly maintained, they can cause trouble.

Trouble in terms of not providing enough electricity (the installation is underpowered and the battery is not being recharged) or too much electricity (causing damage to the electric and electronic components and even damaging the alternator itself).

The first step in finding out that the alternator is faulty is through checking the voltage output.

If you want to check the voltage output on your own, click here to read a separate article on that topic or watch a video tutorial on our YouTube channel.

The solution to an alternator problem is similar to the one with the car starter:

Replacement

Alternators can be bought as a separate part in every better car parts shop.

As with a car starter, buy one with a guarantee and with the same specifications as your old one (size, mount, voltage, and amperage output).

The replacement procedure highly depends on the car model and accessibility.

Some have easy-to-access alternators and some are pretty complicated to reach which highly influences the outcome of the repair (in terms of time and money).

I wouldn’t advise this procedure on your own unless you have some experience with car repairs.

If the alternator is less accessible there will be a lot of picking apart until you actually reach it.

This job can be pretty complicated, so make a good assessment before you start.

Repairing the alternator

Alternators can also be repaired.

In older cars, this was pretty standard and the build-quality of the alternator meant that a repair was possible, even preferable.

But what I’ve noticed is that today’s alternators are not made in the same fashion. The new ones are more complicated to disassemble and repair like they were made for on-time usage.

Have this in mind and perhaps inform yourself before you start the repair. Sometimes buying a new one is the better way to go.

If you decide to repair, you can buy spare parts separately (bearings, voltage regulators, diodes, or else) in almost all car part shops.

If you’re going to DIY, have in mind that repairing alternators demands serious experience and skill. On the other hand, replacing with a new one demands less expertise.

If you decide to visit a professional, prepare yourself for a hefty price tag.

To simplify the matter of repair:

If you have the experience, do the whole procedure on your own (taking off, repairing the alternator, returning on the car). This is the winner in terms of saved money and perhaps, time.

If you have less experience around alternators but some experience around mechanics; buy a new one and replace it yourself.
No experience at all, pay a professional to do it.

4. IGNITION SWITCH PROBLEMS-WHEN YOU TURN THE KEY THE CAR WON’T START

Ignition switches are switches that provide electricity to the car starter at the turn of the key.

The ignition switch is connected to the ignition lock mechanism so when you turn the key, you also turn a switch.

If your ignition won’t turn, you can read how to solve this problem in a separate article on this topic or watch a video tutorial on our YouTube channel.

Like with every switch, this one also wears down. Millions of turns and high amperage cause the switch to malfunction (the contacts simply burn out or get deposits of filth on them).

Here, replacement is the only solution. The ignition switch is sold separately. Prices vary mostly depending on the car model.

Price here isn’t the main problem, rather the replacement procedure.

On most cars, it’s complicated involving taking off the steering, wheel, airbag, plastic trimming, safety bolts, etc.

It can be done on a DIY basis, but only if your good around repairs. Otherwise, leave a professional to do it.

5. FUEL PUMP PROBLEMS

The fuel pump’s main role is to push fuel from the gas tank to the engine.

In past times these pumps were mechanically driven, today’s car fuel pumps are all electric (apart from some rare exceptions).

The pumping is actually done by a small electric motor in a sealed housing. Over time, this electric motor wears out for various reasons and the fuel supply to the engine cuts off.

Most electric pumps are located in the gas tank and are cooled by the fuel itself (this is why driving on a low gas tank for prolonged periods of time will cause damage to the fuel pump).

Replacement is the only way to go as almost all of these pumps are made with sealed housings making them almost impossible to repair. You can take them apart, but can’t put them together.

The replacement procedure depends on the car model and, is in most cases, complicated (involving taking off the gas tank, hard to access places, etc.). There are cases when the replacement is not that complicated, but these are rare.

Of course, it can be done in a DIY way, but a pretty nasty job. If you have no experience, best leave it to a mechanic.

The best way of preventing this sort of problem is either driving with a full gas tank or at least at the middle level.

This way, the fuel pump will always be submerged in gas and have proper cooling.

6. PROBLEMS WITH THE IGNITION SYSTEM

The ignition system is compiled of various parts.

The complexity makes it one of the most common causes of why the car won’t start.

Its main task is to ignite the air-fuel mixture inside the engine cylinder causing the engine to run.

You can see on Wikipedia by clicking here what are the exact parts and how the ignition system works,

You have the old ignition system (with spark plug cables, one ignition coil, distributor, etc) which we won’t be mentioning here as it is almost extinct (remains on old-timers and older type cars)

Here, we’ll mention the modern system which is present in most of today’s cars.

Parts that may cause problems:

Spark plugs (applies to petrol engines)

Spark plugs, as the name says, provide the actual spark for igniting the air-fuel mixture.

They work under high voltage and are directly exposed to high temperatures from the burning mixture. Because of this, they simply wear out over time.

Problems from the spark plugs come from wide electrode gaps, cracked electrodes or insulators. But these appear only after using the spark plugs beyond the recommended maintenance interval.

Forget about this problem if you change the spark plugs on time and use quality ones.

Depending on the car model, mostly a DIY job.

Ignition coils (applies to petrol engines)

Ignition coils have the function of providing a high voltage to the spark plug. No high voltage, no good spark.

The coils can wear out over time as they constantly produce high voltage and are exposed to engine heat all the time (they’re located on the engine, right above the spark plugs).

Ignition coils are meant to be replaced. They can be replaced one at a time (which most people do) or all together in a set.

My recommendation, change them one by one, as they malfunction.

Glow plugs (applies to diesel engines)

The diesel engine ignites the air-fuel mixture in a different manner (highly compressed fuel and air are ignited without a spark).

But to be able to start, when the engine is cold, the engine cylinder needs some pre-heating. That’s where the glow plug comes in.

As with spark plugs, change them on time and use quality glow plugs and there will be no problem.

The common mishap is that only one or two glow plugs fail.

In this case, best change them altogether, not one by one.

Ignition control module (for petrol engines) or glow plug control module (for diesel engines)

Ignition control modules manage the electric current that is fed to the ignition coils.

The control module for glow plugs serves as a regulator for switching on or off the glow plugs as well as a timer for how much the glow plugs are supposed to heat up.

Malfunctions of these components are rare but do happen.

Faulty ignition control modules and glow plug control modules are best diagnosed by an OBD tool.

Replacement of the complete module is the only solution here.

Not a very complicated replacement, you can do it on your own as long as you know the location and you are 100% sure that this is the problem.

Sensors (namely the crankshaft sensor)

Crankshaft sensors are optical sensors that read the movement of the crankshaft and send that data to the engine management system. The “eye” of the whole system so to speak.

These sensors are exposed to all kinds of dirt, heat, cold, and other harsh conditions making them prone to malfunction.

This malfunction is diagnosed with an OBD tool and replaced as a part on its own.

Depending on the car model and accessibility, can be a DIY job.

ECU unit

ECU units are a very rare cause of why the car won’t start.

If it does happen, there was probably some previous mishap that caused it (short circuit, an improper ground connection, high alternator voltage, etc).

Also, a costly problem if it happens. Involves replacing the whole ECU unit, diagnostics, fine setting, etc.

I’ve heard that professionals open and fix ECU units, but haven’t had this experience.

On this part, I wouldn’t recommend the DIY option at all. The actual physical replacement is not that complicated; the procedure after replacement demands serious knowledge.

7. CLOGGED FUEL FILTER OR FUEL LINES

After the pump, fuel goes through a network of fuel lines, a fuel filter, and into the engine intake.

Fuel filters, like other filters on the car, have a regular maintenance interval. Changing them on time and by the book will eliminate these kinds of problems.

Also, use quality fuel and avoid driving on a near-empty gas tank all the time.

Not changing the fuel filter on time will cause the forming of deposits inside which will eventually lead to a clog.

Clogs in fuel lines are rare and are mostly caused by using low-quality fuel as well as prolonged driving on a low gas tank. They can also appear in freezing weather in form of ice buildup in the system.

This repair is tricky as it demands time and experience to find the clog. Especially since the fuel lines are narrow and even a very small particle can mean a lot of trouble.

Changing the fuel filter is less demanding and perhaps more of a DIY job but highly depends on the car model you drive. Some are very easy and some are a nightmare to replace.

8. LOOSE, RUSTY OR DIRTY BATTERY GROUND (“-“)CONNECTION TO THE CAR BODY

Ground connection means the minus connection from the battery terminal to the car body.

The ground connection is equally vital to the proper work of the electric installation and electronics as the plus connection is. It all functions like a water flow; water (electricity) flows from plus to minus.

Loose, rusty, and dirty ground connections are notorious for causing problems that are hard to diagnose.

Very misleading and prone to wild goose chases. Here, even the OBD tool makes mistakes.

So here, proper diagnostics is key and most part of the repair.

A simple solution to this problem is to check all of the ground connections on the car installation. Most important is the one that leads from the car battery to the car body, and from the car body to the engine or gearbox.

In most cases, easy to remove and clean making it a simple DIY job (unscrew or unbolt, take the cable off, clean with sandpaper or a file, return and tighten firmly).

9. DIRTY OR CLOGGED AIR FILTER

As mentioned, the inner combustion engine is highly dependent on proper airflow and air intake.

The air filter serves the purpose of cleansing the air that comes into the engine. Without it, dust, filth, and other particles could cause damage.

Over time, a deposit of dust and all kinds of filth build up on the filter. This causes a clog at the beginning of the air intake and the car won’t start.

The air filter has to be seriously clogged if the car won’t start; you should be able to detect this problem at an early stage as the car won’t have its usual power and will be bogged down.

As with all filters, change it on time and you should be free of this kind of problem.

Definitely a DIY job, if you want to see how to change an air filter on your own, click here to read a separate article on that topic or watch a video tutorial on our YouTube channel.

If you’re not in the mood, a lot of dealers or garages will change it for free if you buy the air filter from them.

10. CLOGGED CATALYTIC CONVERTER

Catalytic converters have the function of cleansing the exhaust fumes. It’s mounted on the exhaust system (exhaust pipes).

Over time, it gets clogged, especially if you use low-quality fuel for a prolonged period of time.

This again causes the lack of proper disposal of exhaust fumes meaning the engine “suffocates” so to say. Proper disposal of exhaust fumes is as important as the air intake.

This fault usually has a warning period before the car won’t start. You’ll probably feel the car bogging down and not having the power it usually has.

Catalytic converters are meant to be replaced when they get clogged. This, in most cases, involves cutting the old one out from the exhaust system and welding a new one on.

This can be a DIY job but in some cases knowledge of welding is necessary; in some cases, the converter is held by clamps that can be unbolted or unscrewed.

All in all, a nasty and dirty job. Alongside that, the price of a new catalytic converter is often a three or even four-digit number.

I would strongly advise you to visit a professional muffler shop and ask before you start the repair on your own.

Often, professional shops have an offer that makes a DIY job simply not cost-time effective.

In recent times, I’ve seen specialized shops that take the catalytic converter down and clean it.

I haven’t tried it but due to the price of a new catalytic converter, well worth the try.

OTHER POSSIBLE REASONS WHY THE CAR WON’T START

The upper mentioned reasons are the most common ones.

However, there are a few more reasons that are worth the mention:

EMPTY GAS TANK

Yes, this does happen to a lot of people, despite warnings and the fuel gauge.

Very common, especially with new drivers or ones accustomed to driving on a low gas level.

The best solution here is prevention. Learn to give the gas gauge a casual look from time to time.

Perhaps the best prevention is, once the gas tank is half empty, fill it again to the brim. This way you’re bulletproof from this problem.

PROBLEMS WITH ELECTRONICS AND WIRING INSTALLATION

Today’s cars heavily depend on electronics. One ECU is more or less a thing of the past. Now it’s three or more followed up by a jungle of wiring, sensors, switches, and else.

This factor alone makes it more prone to failure, especially for high-mileage used cars.

Pay attention to these systems if there have been problems and anomalies such as alternator faults (high voltage output), short circuits (tampering with the installation), or perhaps improperly jump-starting the car.

All of this can cause damage to the sensitive electronics and electric installation and then the car won’t start.

CAR ACCIDENTS AND COLLISIONS

Many cars have a “safe-mode” system.

Through various means (sensors, valves) they can block the ignition system and fuel intake when the car has been in a collision.

This is a great system that saved many cars from catching fire or from other dangers after a car accident.

After repairs are done, the ECU unit needs to be, in most cases, reset with a diagnostics tool. On some cars, these need to be specialized in order to “unlock” the ECU unit.

Especially have this in mind if you’re doing a car DIY job after an accident. Some collisions are not that bad so lots of people try to make a fix on their own, only to finish the job and not be able to start the car.

It cranks but doesn’t start. Then the wild goose chase begins as people seldom think that this may be the problem.

If you visit a mechanic to repair the car after an accident, you shouldn’t have any problems because they will know that this reset is needed.

LOW COMPRESSION (ENGINE IN BAD CONDITION)

Engines have their life-span. However careful you are, sooner or later it will come to an end.

At the end of the engine’s “life”, compression starts to fail, the engine starts burning oil, and eventually, the car will crank but won’t start.

First sure tell-tale sign (besides burning a lot of engine oil) is if the car won’t start in low temperatures (like in the winter). This sign goes double for diesel engines.

If you’ve had an overheating car situation, this can also cause damage to the engine. A blown head gasket can lead to mixing coolant and oil and low engine compression.

The best way to resolve this issue is to visit a good and trustworthy mechanic who will measure the cylinder compression with a specialized tool.

Besides that, he/she can give you a good opinion if the engine is worth the repair.

SYMPTOMS OF A CAR THAT WON’T START AND POSSIBLE SOLUTIONS

At the end of this article, here are some symptoms that you’ll encounter when the car won’t start. Under every tab, you have some possible solutions.

See this as a helper, not a definitive solution since these problems have a wide variety of manifestations and solutions.

The car won’t start but cranks

faulty fuel pump
clogged fuel filter
faulty spark plugs (petrol engines)
faulty ignition coils-one or more (petrol engines)
lack of power supply to the spark plugs (ignition control module, ECU unit, electric installation or else) for petrol engines
one or more faulty glow plugs (diesel engines)
faulty control module for the glow plugs (diesel engines)
clogged or weak air intake (mainly the air filter)
fuel or electric supply is cut off by a security system

There’s no cranking at all

dead or weak car battery
loose or weak connection on the battery terminals
faulty car starter (mainly worn out brushes or rotor, faulty connection to the starter)
faulty ignition switch

The cranking is weak

weak car battery
loose or weak connection on the battery terminals
faulty car starter (mainly worn out brushes or rotor, faulty connection to the starter, worn out bushings)
weak connection of the minus battery terminal to the car body

Car won’t start with a good battery (battery replaced but still cranks poorly)

dirty or loose battery connections on the battery terminals
car starter problems (worn out bushes, rotor, field coils, worn-out brushes, etc.
weak ground connection (for more information click here)
low voltage supply from the alternator-check the voltage input

When you turn the ignition you just hear a clicking sound, no cranking

weak car battery
loose or weak connections on the battery terminals
problems with the car starter (mainly the solenoid but also brushes, rotor, or else)
weak connection of the minus battery terminal to the car body
the ignition switch is faulty

When you turn the ignition you just hear a buzzing sound, no cranking

starter gear (drive pinion) on the car starter needs to be replaced. Most evident in winter when the car needs more turnover power to start

There’s no sound at all when you turn the ignition

dead or weak car battery
loose or weak connection on the battery terminals
faulty starter (brushes, rotor, faulty connection to the starter)-in this case, the warning lights on the dash will go a bit dim when you turn the ignition key for turnover

There’s no dashboard lights, no cranking whatsoever(the car is totally “dead”)

dead or weak car battery
loose or weak connection on the battery terminals

Car won’t start sometimes-cranks but doesn’t start

faulty fuel pump
faulty ignition switch
a faulty ignition module or ignition coil (for petrol engines)
clogged fuel filter or fuel line
faulty glow plug control module (for diesel engines), mostly when the engine is cold
faulty glow plugs, one or more

The car won’t start in cold temperature-does not crank at all

dead or weak car battery
loose or weak connection on the battery terminals
faulty car starter
faulty ignition switch

In cold temperature the car cranks but will not start

low engine compression (for diesel engines especially)
one or more glow plugs don’t work (for diesel engines)
thick engine oil-if the oil viscosity is not suitable for winter it can cause problems
faulty ignition modules or ignition coils (for petrol engines)
clogged fuel filter or fuel lines can especially happen if the fuel doesn’t have any additives and the temperature gets very low
faulty fuel pump

The car won’t start after pouring gas in to the tank-cranks but will not start

many cars need excessive cranking when you empty the gas tank. You’ll either need to crank a lot (which can damage the car starter and deplete the car battery) or have someone to tow you and use that force to start the car (this only applies to cars with manual transmission).
faulty fuel pump-constantly driving on a low gas tank will damage the fuel pump. Emptying the gas tank to the maximum may cause its total malfunction
clogs in the fuel system-filth from the gas tank will arise after filling the tank up. Various particles can get into the fuel lines and fuel filter thus causing clogs.