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Car Won’t Start When Hot

An engine that starts fine cold but is hard to start or won't start after a short stop when hot often points to a failing crankshaft position sensor, fuel vapour issues, a leaking injector or a weak starter.

Normal risk

Have it checked soon. Heat-related failures tend to get worse and can leave you stranded.

Short answer · Why won't my car start when it is hot?

Some sensors, especially the crankshaft position sensor, fail when hot and recover when they cool. Hot fuel can vaporise or drain back if a pressure valve leaks, so the engine cranks but does not fire. A leaking injector floods the engine during the stop. A weak starter can also struggle when hot.

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Safe checks you can do

  1. Note how long it was stoppedFails after 10 to 30 minutes, starts after cooling: a typical pattern.
  2. Listen to the crankingNormal speed but no start points to sensor or fuel.
  3. Read stored codesCrank sensor or fuel pressure codes help.

Questions that narrow it down

  1. Does the rev counter move while cranking?If not, the crank sensor may not be giving a signal.
  2. Does it start with the accelerator pressed?A flooded engine is possible.
  3. Is cranking slow when hot?The starter may be weak.

Possible causes

Listed without ranking. Use the questions above to see which ones fit your car.

  1. Crankshaft position sensorFails when hot.
  2. Fuel pressure lossLeaking check valve or regulator.
  3. Leaking injectorFloods the engine.
  4. Weak starter motorSlow when hot.
  5. Coolant temperature sensorWrong mixture for a hot start.

Questions about Car Won’t Start When Hot

Can I do anything to start it?

Waiting for it to cool often helps, but have the cause found.

Is it the battery?

Usually not, if it starts fine when cold.