How to Repair an Engine Not Running

We are a team of ASE certified mechanics that have created this guide to help you figure out advanced engine no start issues. If you have landed on the page first and you have not checked the easy stuff please visit our, car is not starting guide first. If the battery is good and the engine will not crank over, the next step is to follow our starter's not working guide. If the engine cranks over but is not starting continue through these steps.

Lets Jump In!

Before going any further down the troubleshooting tree it is best to check the fuses, this is easy to do and can be done in just a few minutes using a test light or visual inspection. The fuse panel will be either under the hood, or inside the vehicle under the dashboard. Once you have found the panel, remove the lid, the fuses should be clearly marked, simply turn the ignition key to the on position and begin the inspection or testing.
checking fuses

When you turn the ignition key on or to the crank position does the security light flash? Each manufacturer disables the engine in different ways when in security mode and occasionally the system can become confused due to a glitch or a procedural error, in either case the security system must be reset.
security light blinking

Crank the engine over and listen to how it sounds, does it sound funny or 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 when the engine is cranking over).
compression gauge

Remove the air intake boot or tube to expose the throttle body, have a helper crank the engine over and hold the throttle open about 1/4. With the engine cranking spray starting fluid which you can get at the auto parts store. If the engine starts, you know the problem is fuel related such as a fuel pump or injector issue.
spray starting fluid

If the engine does not start with starting fluid, you need to check for ignition spark by removing the ignition coil or spark plug wire and insert a test light into the boot, crank the engine over and check for spark.

Watch the Video!

Please watch this video of the job being done, then continue down the guide to glean additional helpful information.

If no spark is observed the most popular reason is a failed crankshaft position sensor which is located near the engine crankshaft, at the rear (bell housing), middle (block) or front by the water pump, and is pretty easy to change in most cases. If you need the exact location please ask one of our experts, it's free.
crankshaft sensor

The engine's computer system is run by a main power relay which is named different things from each manufacturer, such as PGM-FI or Engine Control Relay and is located under the hood inside PDC (power distribution center - fuse panel). Remove the lid to the fuse panel or PDC and locate the relay. Have a helper turn the key on while you have your finger on the relay, you should feel a click which means the relay is working. On occasion the contacts inside the relay go bad in which case the relay will need to be tested or replaced.
main computer relay

When all else fails, remove a spark plug to see what color the electrode is, if the plug is dry and clean then no fuel is being delivered, if wet with fuel there is no spark or compression and if flat black the spark plug is fouled and needs to be replaced.
spark plug

Here are additional causes for an engine not to start that are more rare, but they do happen: Water in the fuel, plugged exhaust system, bad PCM, or internal engine damage such as a broken camshaft.


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