How to Diagnose a Car That Turns Over But Won't Start

by Contributor

A car that turns over but won't start can be a real headache and leave you searching for a solution. With most vehicles, there is a specific testing algorithm that you can follow to diagnose the cause of an engine that turns over but won't start. Here's what you need to do to find out the cause of your problem, and get your car back on the road.

Make sure that you have enough gas in your car. This sounds like common sense but many people don't think to check this before wondering why their car won't start. Try to refill your tank when it is no less than one quarter full, or you risk getting stalled or stuck somewhere.

Verify that the battery has a full charge. A battery with a low or partial charge can cause the engine to crank too slow preventing it from starting. Sometimes a jump will fix this problem, but if your battery is more than five years old you should consider replacing it, especially if winter is only a few months away.

Check to see if your fuel pump is turning on. This can easily be done by putting your key in the ignition, turning it to the "on" position, and listening carefully with your ear pointed toward the back seat. If your fuel pump is working you will here an electric "whirring" noise for about 2 seconds every time you cycle the key on and off. If you hear nothing then your fuel pump is faulty or not getting any power.

Find out if the engine is getting gas to it. Sometimes a plugged fuel filter or a problem with the fuel injectors can prevent the engine from getting any gasoline. To check this remove the air cleaner and smell inside the throttle body or air cleaner housing. If the engine is getting enough gas you should be able to sense a strong gasoline smell due to the amount of uncombusted fuel left inside the intake manifold.

Determine whether the spark plugs are firing. If there is plenty of gas but no spark, the engine will crank but not start. Unplug one of the spark plug wires and plug in a spark tester. Have a friend get in the car and crank the engine while you watch to see if the spark tester illuminates. You can usually purchase a spark tester at an auto parts store for about ten dollars.

Tips

  • check Be very careful when working on any type of vehicle. Make sure that you are wearing safety glasses and follow every possible safety precaution.
  • check If you can't figure out why your car won't start after following the above steps, it could be an advanced computer or engine problem. In this case, it's best to consult a professionally trained mechanic to avoid doing damage to your engine or any of your car's components.

About the Author

This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information. To submit your questions or ideas, or to simply learn more about It Still Runs, contact us.

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