Engine Wont Start Repair Guide

Why your car will not start troubleshooting tips and repairs by the pros.

Updated: February 26, 2016

When your car won't start it can be very frustrating. Car owners all over the world experience this problem at least once in their driving lifetime, but don't worry we have you covered with this easy to follow guide created for people just like you to save money and be informed. The first thing you want to remember is to stay safe by using services like Yelp and Google to find the best repair shops and towing services in the immediate area. In the meantime please read this article of the possible causes of your car problem, be informed for the best repair experience possible.

There are many systems and parts involved when your engine wont start from the easy to fix solutions such as a loose battery cable, to the more involved problems such as a failed crankshaft angle sensor which we will go over in this guide.

When you, the tow truck driver or the repair garage has figured out the problem you will have a better idea on where to go from there and what to do about the repair. Answer these questions throughout our guide which will help you pin point the problem.

Car Not Starting Questionnaire - What is happening when you try to start you car?

1. Can you turn the ignition key? Yes or No - If you answered no please visit - Ignition Key Stuck

2. If the key turns to the "ON" position (without cranking) do the lights on the dash come on? Yes or No - If no, please visit - Battery Goes Dead Overnight, How to Check a Battery or Battery Replacement

3. If the lights come on the dash when the key is "ON" but when you try to crank the engine over do all the lights go out? Yes or No - If yes, please visit - All electrical goes dead, if no please continue.

4. When you turn the key to the "crank" position and the dash light stay bright is there a security light flashing? Yes or No - If yes, exit your vehicle and close all vehicle doors, lock and unlock the drivers door or the rear hatch if equipped, this should reset the alarm or immobilizer system to allow the car to start.

Also, frequency chips are used inside the key so if a non-original key or a key copy is used this will not disarm the security system. If no please continue. (Some vehicles will allow the engine to crank but not start in the security mode). If needed, dealer will need to check ignition key and replace.

5. What happens when you turn the key to the crank position? Nothing?

a. Check to see if the gear selector is completely in the park position for car equipped with an automatic transmission and for stick shift vehicles be sure the clutch pedal is depressed completely. Be sure to check to make sure the floor mat is not obstructing the pedal travel.
b. The starter motor could have failed please visit - Starter Motor Replacement
c. If your car has an automatic transmission try moving the gearshift selector to the neutral position, if the the starter works you have a natural safety switch that has failed, to replace or test it please visit - Testing a Neutral Safety Switch

6. If there is a rapid clicking sound when the key is turned to crank position or if the engine cranks over slowly and then stops and then you hear a rapid clicking sound the battery is weak or discharged. Please visit - Battery Load Test and Alternator Testing (Note: A general rule of thumb is if the battery is more than 3 years old it will be prone to failure.) If the battery is dead and you need to get the car going again please visit How to Jumpstart Your Car for the correct method. If when you you try to crank the engine over and all of the electrical goes out it can be a bad or loose battery cable connection please visit - Bad Battery Connection  (Note: The connection of the jumper cables is important not to connect the negative to the positive battery terminal or you can cause electrical damage.)


If the engine cranks over normally but wont start up continue with our questionnaire.

Step 1

It is not uncommon for a car to simply run out of gas even though the fuel gauge is showing some gas in the tank (usually about 1/4 tank or all the way full) unfortunately it is difficult to tell if there is gas in the tank without the gauge working. If this is the case the engine might start for a short time then stall out, or stall when you push the gas, also the fuel pump may sound a little different than normal. The best way to tell is to estimate the last time you fueled up. If you suspect the fuel level sender has failed please visit - How to Replace a Fuel Level Sender. If the car has plenty of fuel please continue.

Step 2

The car's computer is very helpful in these situations because it can store trouble codes which will point you in the right direction. Today's car's are easier than ever to read the codes and it doesn't cost much for a code reader from places like Amazon. Please watch - How to Read Trouble Codes.

Some of the most common problems for an engine that wont start is:

a. Crankshaft angle sensor failure
b. Fuel pump operation failure
c. Computer or engine fuse blown, please visit - How to test a fuse
d. If the fuel pump is fairly new it could be the relay that controls it - How to replace a fuel pump relay

If these items are okay please continue to the next step.

Step 3

Mechanical failures can plague the engine as well, such as a bad timing belt or chain and even most catastrophic failures such as an internal engine failure (throwing a rod). These problems are usually accompanies by a strange engine noise, please visit - Abnormal engine sounds

New Timing Belt

Step 4

An ignition switch can fail which doesn't allow the electrical currant to transfer to the car's computer and electrical system. Because this unit is a switch that can have up to eight individual connects to various systems it can wear causing high resistance which produces an open circuit. Try turning the switch "ON" and "OFF" rapidly this can clean the connects momentarily allowing the car to start.

Ignition Switch

Step 5

Bad or loose connections at the starter motor itself can cause the starter not to operate even though the starter motor is in good shape. If possible grasp the trigger and main power cables to make sure they are tight. Most of the time these wires are under the engine and can be difficult to access.

Checking Starter Connections

Step 6

Internal battery problems can cause the engine starter not to receive the amperage needed for the starter to operate even though the voltage level is sufficient. This is typical of older batteries and is very common. This condition can cause the starter to make a single click and then nothing after. This has happened to us many times at our repair shop. Battery replacement is very easy and most people can do it themselves with simple tools which can save money you throughout your diving lifetime.

Battery Condition Checklist:

  • Check for the battery sides bulging outward, this is a sign the battery is failing
  • Test the battery condition by performing a simple in vehicle load test
  • Check the cables for corrosion
Please visit - Battery Replacement

Battery Replacement

Step 7

The battery cables are used to transfer the battery voltage to the engine starter and to the computer system, these cables are subject to battery acid which can produce internal cable failure. When this condition occurs the car will act much like a dead battery by not allowing the voltage to continue to the starter motor. Check both the negative and positive battery cables for abnormal bulging, weakness and corrosion.

This problem can be sometimes overlooked by most mechanics and can be intermitted. If you are having this problem be sure and mention to the repair shop to check the positive and negative cables.

Battery Terminal Corrosion

Step 8

The starter solenoid is used to engage the actual motor portion of the starter and engage the gear into the flywheel of the engine. If the solenoid fails it will not push the bendix gear into the flywheel. If this happens you will hear the starter motor turn but the engine will not crank over, in most cases the starter will need to be replaced. Please see - Starter motor replacement

Step 9

The engine flywheel or flexplate is attached to the engine crankshaft and is used together with the starter to crank the engine over, on rare occasions the flywheel or flex plate can break which renders the starter inoperable. This condition can be difficult to determine without removing the starter motor or the transmission to inspect and replace the flywheel. Visit - Flywheel Replacement and Transmission Removal

Also See: Engine is not cranking over Internal Combustion Engine Basics

Every car engine needs three things to happen to crank over and run, compression, fuel and ignition. Engine compression is the result of the proper correlation of the engine crankshaft, camshaft and valve system for more information please visit - How An Engine Works

Checking engine compression is not to difficult and can be done with everyday tools and a compression gauge remove the engine fuse and one of the easiest spark plugs to perform a compression test. If compression readings are between 120 and 180 psi. the compression is normal. The engine will not run or run poorly if the compression reading is below 80 psi.

Most of the time if one cylinder has the correct compression the engine will start and run, if one or more cylinders have low compression the engine will misfire and have a rough idle. When the compression is low or non-existent the engine will crank over freely with little resistance to the starter. Low or no compression can be caused by a broken timing belt, timing chain or worn piston rings.

If the engine has been severely overheated it can cause the head gasket to leak which will fill the cylinder with coolant not allowing the engine to turn over. To see a detailed guide on this procedure check out - Testing Engine Compression.

Cylinder Compression Test

Step 10

The fuel injection system of an engine is used to deliver the proper amount of fuel at the correct time (compression). This is perform by the fuel system which consists of a  fuel injector for each cylinder, a fuel pump which is located in the fuel tank, fuel lines that reach the tank and head up to the engine and onto the fuel rail where the injectors reside. This entire system is controlled by the engine computer and if there is a problem the computer will not trigger the injectors to allow fuel to enter the engine. Use this guide to determine if this could be the problem with your engine. Testing The Fuel Injection System.

Fuel Injector

Step 11

Your engine's ignition system is designed to ignite the fuel air mixture inside the combustion chamber via the spark plugs. This is done by using an ignition coil, a crankshaft and camshaft angle sensor along with the car's computer or PCM (Power Control Module). This system can stop working due to a blown fuse or if the crankshaft angle sensor has failed which is very common. Testing the ignition system is not to difficult and can be done using a test light. Follow this easy step by step guide we have created for you - Testing The Ignition System

Testing Ignition System

Step 12

If all three systems check out okay and your engine still doesn't not run, please continue with our guide.

There is one easy problem that most people overlook when their engine will not run, it is the condition of the spark plugs. If they are fouled due to excessive fuel, wear or carbon build up the engine may not start, remove all spark plugs to inspect for a black soot which means the plugs have shorted to their insulator. In this case the spark plugs must be replaced with new plugs which should be done with a spark plug socket to protect the plug from breakage. To change your spark plugs please follow this step by step guide - Replacing Spark Plugs

Fouled Spark Plug

Step 13

The catalytic converter is used to help clean the engine's exhaust emissions and is part of the exhaust system of your car. As the converter ages it can break apart and block the exhaust system not allowing the engine's exhaust gases to exit the engine. This condition will not allow the engine to run. To check for this problem disconnect the head pipe from the exhaust manifold. Please Visit - Exhaust System Removal

Plugged Catalytic Converter
If somehow you get the car going again take note of the things you did prior to the the car starting, and if something is happening while the engine is running such as black, blue or white smoke coming out of the tail pipe take note. Black smoke could mean a fuel injector is struck open or the fuel pressure regulator has failed. White smoke or steam from the tail pipe could mean you have a blown head gasket. This can help in the repair process by pin pointing the system or systems that were effected. For more information on this subject please visit - Blown Head Gasket Testing

Blown Head Gasket Testing
Many subsequent conditions which are more difficult to detect that can occur which will cause your engine not the start and run such as:

  • Water in the fuel tank
  • Electrical and engine system wiring harness failure
  • Computer malfunction
  • A previous repair could have failed such as a timing belt replacement gone bad
  • If you drove through a deep water puddle the engine could have ingested a large amount of water causing electrical components to get wet.
Before the engine would not start did you notice anything out of the ordinary while the engine was still running such as low power, check engine light on this could aid in the troubleshooting and diagnosis of the problem, be sure to mention anything you noticed before the engine would no start to our repair technicians. Ask us a Question or your mechanic.

It can help to research other people's problems by using our previously answered non engine starting problem from one of our certified technicians. Engine Not Starting Questions and Answers

Common Engine Problems

Also Check the national car complaints data base for similar problems - Safercar.gov

Best Practices

  • Check the easiest systems first.
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