Wont Start

Step by step guide on how to repair an automotive engine that will crank but wont start. This article pertains to all vehicles except electric.

Difficulty Scale: 4 of 10

Tools and Supplies Needed

  • Flashlight
  • Test light
  • Wrench set
  • Screwdriver set
  • Code scanner tool
  • Fuel pressure gauge
  • Protective eyewear and gloves

Begin with the vehicle on level ground in park with the emergency brake set.

Automotive Engine

Step 1 - Once the ignition key has been activated and the starter is operating properly observe the cranking rhythm and sound of the engine. If this process is not typical of a normal cranking operation internal engine damage could have occurred. Abnormal engine noises could inhibit the engine from running, such as a broken timing belt or chain, piston connecting rod failure.

Automotive Engine Timing Chain

Step 2 - The computer system or PCM controls every aspect of the engine operation. If a sensor such as a crankshaft angle sensor has malfunctioned it will cause the engine not to run. Use a scanner tool to check for trouble codes and repair as needed. If the trouble code present does not pertain to the engine not running such as an EVAP code, ignore it until after the engine is running. Sometimes the code will clear itself after the engine is running. (Note: Sometimes failures occur that cannot be detected by the computer, example: If the fuel pump fails, the computer cannot detect the failure.)

Code Reader

Step 3 - The power distribution center of a vehicle houses fuses which project electrical circuits, including engine management components. Inspect and test fuses to ensue proper operation, replace any shorted fuses.

Checking Fuses


Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2014-10-24)