As an auto electrician, I have come across so many simple issues that just needed a simple screwdriver to get your car cranking over. So this is my mega-post-on 16 reasons why your car turns over but won’t start. It all comes down to Fuel, Air, and Spark.
9 times out of 10 it is a battery problem, either a flat battery or a low capacity battery due to age. Car batteries only last between 3-5 years depending on use and road conditions. So let’s dive into why your car cranks over but won’t start. Often it is an easy fix but sometimes it will be a harder problem to solve.
Table of Contents
- 1 16 Reasons why your Car won’t start but the battery is good
- 2 The car won’t start clicking noise heard
- 3 Battery Terminals
- 4 Spark coil pack and distributer leads
- 5 Fuel Injection Problem
- 6 Car blown fuses
- 7 The car fuel pump not working or a blocked fuel filter
- 8 What sensors can cause a car not to start?
- 9 Blown Head gasket fix
- 10 Dirty Idle position valve or PCV – (IAC or IPV)
- 11 Broken Timing Chain or Belt.
- 12 Starter motor failure symptoms
- 13 Engine Security system
- 14 The car is in park but will not start
- 15 The car won’t start but the radio works
- 16 The diesel engine turning over but not starting
- 17 Conclusion
16 Reasons why your Car won’t start but the battery is good
This is when we try and work out if it is a fuel, spark, or air problem. If the battery is good then check the following electrical connections in your engine bay.
- Battery terminals are tight.
- Leads from the coil pack or distributor are connected.
- Spark plug leads are pushed on and connected.
- Fuel injector leads are connected and tight.
- Fuel injectors working and not clogged or faulty.
- No fuses are blown.
- The fuel pump fuse is ok and the leads are connected.
- The fuel filter is blocked.
- The car is in the park position and the foot brake is pressed on if required to start.
- The air filter is clean and the sensors are connected.
- Blown head gasket leaking coolant into the engine.
- A dirty Idle position valve or PCV – (IAC or IPV) is very common this usually causes a rough idle fault, and trouble starting.
- The timing belt or chain is broken or out of alignment.
- Starter motor failure or worn drive motor sprocket.
- Security system, is the engine immobilized check the key battery and replace or try another key.
- Engine management sensor preventing the engine from starting such as Low oil, low coolant, TPS sensor faulty, Crank sensor, etc.
The car won’t start clicking noise heard
This is an easy fix if your car won’t start but you hear clicking noises then it is often a flat battery. The reason for this is the starter motor pulls a huge amount of current on startup, from about 50 amps to around 250 Amps for a larger V8 diesel motor.
If the battery is not charged fully and is less than 12v the huge current draw will stall the starter motor. This in turn pulls more amps until the battery drops below 10-11 volts and the starter motor relay drops out.
The battery then has no load so the voltage rises back up to 12v and the relay kicks in again. It is a constant cycle of clicking noises as the starter motor relay is stopping and starting.
The easy fix is to charge or replace the battery. To get you out of trouble you can jump-start your car from either another vehicle or use a portable lithium-ion jump starter.
Sometimes a reason that the car battery is not charging is that the alternator has failed. Check out these tips on how to test an alternator with or without a multimeter.
If your battery terminals are not tight this causes a hot joint between the wires and the battery terminals. In turn, this causes the voltage to drop between the battery and the starter motor. So even though your battery is good the voltage supplied to the starter motor is less than required.
Check by trying to turn the battery cable lug around, if it moves tighten it.
Corrosion on the battery terminals can also cause lower amps to be provided to the starter motor. Clean up the corrosion and use an electrical contact spray to prevent further corrosion. On my battery terminals, I like to use Dielectric grease, which is a silicone-based grease that repels moisture and protects electrical connections against corrosion.
Don’t forget to charge your battery if it is going flat. I like to use these smart car and motorcycle chargers on my vehicles. The batteries tend to last longer.
Spark coil pack and distributer leads
The spark coil pack, distributer leads, and CDI are used to provide a high voltage to each spark plug. If any part fails you can get a ground fault causing no spark. Which means the car turns over but won’t start.
A quick test for spark is to remove one spark plug connect it back into the spark plug lead and touch it to a metal-earth part of your car using a pair of insulated pliers. Get someone to crank over the car and look for a spark coming from the spark plug. If you have spark then your problem is else ware.
If you have no spark then your problem with either be a bad spark plug, faulty leads, burn out HV coil, faulty distributor on older cars, or bad CDI (Capacitor discharge ignition)
Fuel Injection Problem
New cars and motorcycles use fuel injection rather than a carburetor. This is more efficient but also can be more complicated as there are more electrical components.
I have seen a few fuel injectors go bad over my time but it is an easy fix and will show up in the fault code list by using an OBD2 scanner. I use a Bluetooth OBD2 scanner on my Yamaha MT07 as well as all of my vehicles. This way it is nice and portable and can be used on my phone.
When a fuel injector goes bad often a car will still run but have problems starting, It will run very rough and often shows an engine warning light. An OBD2 scanner is best to diagnose this fault. Low pressure in a fuel rail can be caused by a leak, faulty injector, or bad fuel pump.
I have seen people remove each injector and crank the car over. This will squirt some fuel out of the injector. Be careful doing this as petrol gas is very flammable. Replace the fuel injector if it is faulty or blocked. You can also try a fuel injector cleaner which will flush out build-up inside the fuel injector.
Car blown fuses
Fuses only fail if there is a high current draw often down to earth. Usually, this is caused by a failure in the wire insulation or water that has gotten into the electrical component somehow.
The only way to check the fuse is to pull the fuse out of the fuse block and test and inspect each fuse. Use a multimeter set on Ohms to read the resistance. Good fuses will read close to 0 ohms whereas a blown fuse will be an open circuit or many megaohms. The see-through window on each fuse is a guide if you don’t have access to a multimeter.
There may be a few locations for your fuse blocks, often they are found in the engine bay and down underneath the steering wheel.
The car fuel pump not working or a blocked fuel filter
Part of a regular service is to replace the fuel filter. The fuel filter replacement interval is around 20,000 to 30,000 miles or every 2 years whichever comes first. This is dependent on your car’s make and model.
A blocked fuel filter will make the pump work harder and can starve the car of fuel. It can also cause the fuel pump to fail and burn out.
The fuel pump can also fail if you let the fuel tank get close to empty. This is because the pump can run dry and not be lubricated by the fuel. Dirt, sludge, and contaminants will also be picked up if the tank is close to empty. This is why I always fill up my car when it is close to 3/4 empty.
On my Toyota Highlander, the fuel pump failed after 200,000 miles. This was just unlucky as the pump motor failed and was not pulling any amps. This was the reason my car turns over but won’t start.
How to diagnose a failed fuel pump?
Start by turning the car to AUX and listening for the fuel pump to start. It should sound like a small electric pump and may cut out once it has built up to pressure.
If you don’t hear any pump running, give the fuel tank a hit with your hand or a rubber mallet from underneath the car. This may dislodge anything that is blocking the fuel pump as it is submerged in the fuel tank on most modern cars.
Check for a blown fuse. If you can’t hear the fuel pump running and the car won’t start then you most probably have a failed fuel pump.
Spray starter fluid in the air intake duct and start the car. If it runs on that, you have a fuel problem.
What sensors can cause a car not to start?
A crankshaft position sensor (crank sensor), cam sensor, coolant sensor, mass airflow sensor, MAP sensor, and Oil presser sensor can all cause a car not to start depending on its make and model.
- If the MAF sensor has failed then it won’t detect any air coming in, the engine probably won’t start or if it does it will run poorly.
- If the crank sensor has failed then the onboard computer can’t determine where the crank and/or camshaft position is, then it won’t know when to activate a fuel injector or fire a spark plug. Which then means the car won’t start.
How to test crankshaft position sensor.
If your crank position sensor is bad then the car won’t start. An easy test is to crank the car over and look at the tachometer or RPM gauge. If the crank positions sensor is bad you will have 0 RPM if it is good it will rise to around 200 RPM starter motor crank speed.
All cars are different and have different engine management sensors. You may have to check the workshop manual for your vehicle to see what sensor is bad.
Blown Head gasket fix
If you have a blown head gasket on your car you will find that you will lose compression and or coolant will enter the cylinder. This will make the car hard to start and can cause extra damage to your engine over time.
A quick tip is if you find that the coolant reservoir level is going down quickly without an obvious external leak you could have a faulty head gasket. A quick fix is to use some coolant stop leak for engines. Follow this post on how to fix coolant leaking from the engine block without tools.
Dirty Idle position valve or PCV – (IAC or IPV)
An idle air position valve is an automatic valve that sets an air-fuel mixture ratio to help start your can and run smoothly at idle. The idle air control (IAC) valve is located on the throttle body of fuel-injected engines. It essentially acts as a bypass of the throttle body plate.
If your idle air position valve (IAC) is clogged with dirt it won’t move freely and you will have the following symptoms.
- Trouble Starting
- Poor/Rough Idling
- Car Starts, Then Dies
To fix the idle position valve remove it and clean it with some cleaning solution spray. I like to use some solvent or carburetor cleaner. If it is very old you may just like to replace the IAC they are cheap.
Broken Timing Chain or Belt.
A broken timing chain or belt is a major failure and will stop your car dead with a loud bang and the belt snaps and the pistons slam into stuck open valves.
Do not try and start your car if you suspect a broken timing belt as this will cause more damage to the engine. You will be quickly able to see if the timing belt is broken by taking off the engine rocker cover and inspecting the belt.
A tow truck will be required and a qualified mechanic to repair or replace the engine. Many dollars will be required for this fix so always replace the timing belt according to the manufacturer’s service interval. Usually around 150,000 Km or 95,000 miles.
Starter motor failure symptoms
The starter motor engages a spring-loaded sprocket to turn over the engine. They are very reliable but can fail due to age and abuse like constant stopping and starting. If you hear any of the following noises coming from the starter motor then it could have failed.
- Buzzing Noise when trying to turn the engine over.
- Loud Clicking is similar to a flat battery but louder.
- Grinding Sound like metal on metal gears.
- The whirring Noise is like a motor spinning without a load attached.
Holding the start key over if the car won’t start is bad for the starter motor as it will heat up very fast. Only turn your car over for a few seconds at a time. Hundreds of amps are flowing through the starter motor and we don’t want to burn it out.
Starter amp draw chart
There are so many variables in how many amps a starter motor draw. So I have included a chart with some basic parameters so you know what size jump starter you may need.
|Car Engine Starter Amp Draw Chart
|Gas / Petrol
|Up to 150 Amps
|Up to 350 Amps
|Gas / Petrol
|Up to 210 Amps
|Up to 450 Amps
|Gas / Petrol
|Up to 250 Amps
|Up to 650 Amps
Engine Security system
All modern cars have some sort of engine immobilizer system. In modern cars, it is an RFID engine lock. In arming mode, when the key gets close to the detection circle diameter usually between 5cm and 100cm the car will be disarmed automatically.
In older cars, you may have to press an unlock button on the car key fob to disable the engine immobilizer alarm.
If the battery gets depleted in some older model cars you may not be able to disable the alarm and the car won’t start. Sometimes there is a bypass to start the car without the remote but it is model specific and will require the key to be turned to aux and back to off, a number of times.
I like to carry spare remote key fob batteries in the glove box just in case the battery goes flat when I am out. Or you can change it out every two years to be safe.
If your car turns over but won’t start, try another key fob. I have seen them go bad especially if they get wet. Corrosion sets in and the immobilizer won’t work anymore.
You can dry out a wet car remote in a sealed bowl of rice. If the car remote has started to corrode you can try cleaning it in methylated spirits and some cotton wool.
The car is in park but will not start
Most modern automatic cars require it to be in the park position and the brake pedal pressed down. On rare occasions, the park or brake limit switch may be faulty. Move the gear selector to free up the limit switch. Do the same with the brake pedal.
The car won’t start but the radio works
Most probably you have a flat battery it is the same condition as if the starter motor is clicking but there is not enough power to pull in the starter relay. Car radios have a very good range of voltage that they can run on due to their low power usage. I have seen a car radio run on 8V.
Charge the battery or try a jump starter to see if the vehicle will start.
The diesel engine turning over but not starting
Diesel engines use a glow plug to provide heat to fire the engine. These glow plugs need to be warmed up before you try and start the diesel engine otherwise the cold fuel can cause difficulty starting the engine.
Most diesel engines have a glow plug LED indicator once you turn on the ignition. This will go out after a few seconds which is an indication that it is safe to start the engine. Often I have found that if a car battery is on its way out or getting flat I will need to pre-warm the glow plugs longer to have the diesel engine start easily.
You should also check the glow plug relay: The glow plug timer (or control module): The glow plugs themselves for correct resistance.
With a Multimeter, we can measure the supply voltage, the timer aka control module, and the resistance or continuity.
To measure the resistance of the glow plug use a multimeter with the selection on OHMS. Place the red lead on the glow plug active terminal and the black lead on the earth of the engine or Negative of the battery. New glow plugs should have a resistance of 1-5 OHMS.
Any glow plug with a resistance value say over 10 OHMS is defective. Replace it.
If you follow the above tips your will be able to work out the reasons why your car turns over but won’t start. The majority of car starting issues can be put down to 3 areas. Fuel, Air, and Spark.
It is a process of elimination but shouldn’t take you long to work out the issue. Otherwise, it is off to the garage to spend your hard-earned cash on hopefully a quick fix.
I am a qualified Industrial Electrician for the past 20 years and I love to share my knowledge on home repair and maintenance jobs.
I love fast toys like Motorcycles, Cars, Jetskis, Boats, and Computers so writing about them is easy. Working on them is fun.
To keeps costs down I do all my own mods, repairs, and servicing. These skills I want to share with everyone. DIY is a skill everyone can learn.