How to Repair an Engine From Not Starting

 There is a difference between an engine that does not start (run) and one that does not crank over. An engine that does not crank over has to do with the starter motor and is a separate issue from an engine that does not run. If your engine does not crank over refer to the lower part of this guide (starter motor image).

What goes wrong?

 An engine demands three things to run, compression, fuel and spark. If one of these components is missing the engine will not start and run.

Let's Fix It

Observing lights and sounds when the engine is not starting is essential, these steps can give you a direction to proceed which are listed in order of difficulty.

  1. When turning the key to the "crank" position does the security light flash? Each manufacturer disables the engine in different ways when in security mode. Occasionally the system will become confused due to a glitch or a procedural error meaning the alarm system must be reset.
  2. Run the codes! a scanner can point you in the right direction or to the system that is not working, simply plug into the diagnostic port to gather the code(s) and look up the code meaning on Google.
  3. An advanced CAN scan can be used to evaluate the entire electrical system of the vehicle which is quickly becoming more useful than the traditional engine scan, this can help pinpoint the source of the trouble. A CAN scanner starts at $34.00 on Amazon.
  4. It needs to be quiet for this next test, turn the ignition key "on" without cranking the engine over. You should hear an electric pump in the fuel tank run for about five seconds (a low hum). If you hear nothing something has failed in the pump electrical system such as the fuel pump relay, fuse or fuel pump (most popular). Sometimes you can get the car going with a hammer or large object by rapping the bottom of the fuel tank which can coax the pump into working again (this works very well). If the car starts the fuel pump is bad and needs to be replaced.
  5. Most cars have a mass air flow sensor (MAF) which sends feedback data to the computer to trigger fuel to be allowed into the engine, when this sensor fails the computer will restrict fuel causing the engine not to start. Disconnect the MAF sensor and try again, if the engine starts the MAF needs to be replaced.
  6. Next, crank the engine over and listen to how it sounds, does it sound faster than usual? This can mean the timing belt or chain has failed causing the engine to have no compression. Perform a compression test to confirm the failure, observing the engine camshaft rotation through the oil filler cap on the valve cover will also confirm the issue (camshaft not turning).

Minor testing

  1. Check the fuses, this is easy to do and can be done in just a few minutes using a test light or visual inspection. Fuses will be either under the hood in the fuse panel or inside the car in the interior fuse panel which are clearly marked, simply remove the panel lid and begin testing/inspecting.
  2. Spraying starting fluid into the throttle body or a vacuum line while cranking will help determine if the problem is fuel or ignition related. If the engine starts (gas pedal depressed slightly) it tells you the problem is fuel related. If the engine runs on starter fluid there is a fuel delivery issue. The car's fuel pump resides at the top of the list for this system failure. Located in the gas tank the fuel pump is an electrical motor connected to a fluid pump which fails. Some cars have an access hatch in the trunk or under the rear seat to help service the pump while others the gas tank will need to be removed.
  3. If the engine does not run on starting fluid the ignition system could be to blame. Remove the ignition coil or spark plug wire and set it next to a good ground (about a 1/4 inch - 8mm) or insert a test light into the boot to check for spark. If no spark is observed the most popular reason is a failed crankshaft position sensor. This sensor is located near the crankshaft at the rear (bell housing), middle (block) or front of the engine and is pretty easy to change in most cases (When the crank sensor goes out it usually will not set a trouble code).
  4. When the ignition switch is turned on you should hear the main system relay pull its contacts together which supplies power to the computer systems. This relay is named different things from each manufacture such as PGM-FI or Engine Control Relay which is located under the hood in the fuse and relay panel or PDC (power distribution center). Remove the lid to locate the relay. While touching the relay have a helper turn the key on, you should be able to feel the relay work (small click). If not, test the relay or swap it out for a different relay in the panel to see if that works, this will work for the fuel pump relay as well.
  5. Pull a spark plug! This is easily done and by observing the condition of the plug it can give a clue to the problem. If the spark plugs are dry suspect fuel issues, if wet with fuel suspect an ignition problem and if the plug is flat black the electrode is shorted not allowing the spark to jump the gap, replace the spark plugs.

Additional non-starting issues

Watch the Video!

My engine is not starting?

 A starter motor is used to rotate the engine over to begin the combustion process which is controlled by the ignition key, start button or fob. A flex plate or flywheel has a gear lined with teeth around the outer ring called a ring gear and is bolted to the engine crankshaft which the starter uses to operate. The starter motor pulls the most amperage of any other component of the car so the battery must be in good condition.

 When the engine will not crank over the problem can be isolated to three separate areas of the car. It could be a battery or connection issue, a starter motor or its trigger system or the engine or one of it's accessories is locked up. Some problems will be easy to fix while others can be a little tougher.

How much will it cost?

 The cost of a starter problem can vary from no charge to hundreds of dollars, so it is important to get a clear idea of what's wrong. For example a loose battery cable costs nothing to tighten, just a wrench. Repair shop or dealership labor times for a starter replacement can generally range between $85.00 to $280.00 depending on location (some manufacturers locate the starter under the intake manifold), the part can cost between $80.00 to $220.00.

Let's get started

Repairs are in order of difficulty.

  1. If the lights go dim or out this can mean one of two things (this can be accompanied by a ratcheting sound) either the battery is weak and the battery needs to replaced which typically happens between 3 and 4 years or the battery cables are loose. There can also be corrosion on the battery terminals inhibiting the current flow which must be cleaned.
  2. When the key is turned to crank the engine do you hear nothing and do the dash lights stay bright? If so look to see if the security light is flashing which tells you the security system must be disabled. If the light is not flashing try to put the car in neutral and crank the car, if it starts the gear range sensor (neutral safety switch) is bad. On standard transmission vehicles check to see if the floor mat is lodged under the clutch pedal not allowing it to be fully depressed.
  3. The next step is to check the starter system fuses and starter relay which will be located in the fuse panel (PDC - power distribution center) under the hood. The location of these components will be listed under the lid of the panel, in your owner's manual or you can ask our mechanics for locations. Replace any blown fuses.
  4. If the security light is not flashing have a helper hold the ignition key in the crank position or rapidly press the start button while tapping the starter housing with a hammer, if the engine starts the starter needs replacement.


The starter solenoid (small round electrical component  ttached to the starter motor housing) is responsible for the starter motor operation and must receive a voltage signal from the ignition switch. If everything before this point looks okay you need to test the solenoid trigger wire for power when the key is in the crank position to determine the condition of the starter. The starter motor is usually underneath the engine and on the right or left side at the rear of the engine block (it can be under the intake manifold like on some Nissan, Cadillac and Infiniti V8 engines. In this case it's best to find the wire in the loom or at the relay). Please use our starter motor and trigger test guide to help with this issue.


Ask our technicians (free)

Article published