* Vapor lock: This is a classic culprit, especially in hotter climates. Fuel vaporizes in the fuel lines or carburetor (if equipped), preventing liquid fuel from reaching the engine. The cooling-off period allows the fuel to condense and return to liquid form.
* Crankshaft Position Sensor (CKP) or Camshaft Position Sensor (CMP) issues: These sensors tell the computer the engine's position to time the ignition and fuel injection. Heat can sometimes cause these sensors to malfunction temporarily. They may work again after cooling.
* Ignition coil overheating: Similar to the sensors, ignition coils can overheat and fail intermittently, especially under load. Cooling down resolves the problem temporarily.
* Mass Airflow Sensor (MAF) issues: A faulty MAF sensor can provide incorrect air-fuel mixture readings, leading to starting problems. Heat can exacerbate these problems. While less likely to be directly heat *caused*, it could be worsened by heat.
* Fuel pump relay or fuel pump itself: Although less likely to only exhibit problems *after* running, a weak fuel pump might struggle under heat, delivering insufficient fuel. It might recover after cooling.
* Loose or corroded connections: Heat expansion and contraction can affect connections, intermittently disrupting the electrical system.
* Low fuel pressure: The fuel pressure might drop slightly when hot, resulting in a no-start condition. This could be due to a failing fuel pump, pressure regulator, or other fuel system component.
Troubleshooting Steps:
1. Check for vapor lock: If it's hot outside, feel the fuel lines near the engine. If they're unusually warm, this is a strong indicator. Consider adding fuel line insulation.
2. Check the engine bay temperature: Is it excessively hot compared to other vehicles? This could point towards a general overheating issue.
3. Have the diagnostic trouble codes (DTCs) scanned: A professional mechanic or OBD-II scanner can retrieve any stored trouble codes, offering clues to the problem.
4. Inspect the ignition system: Visually check the ignition coils, wires, and distributor (if applicable) for signs of damage or overheating.
5. Test the fuel pressure: A mechanic can measure fuel pressure to determine if it's dropping when the engine is hot.
6. Check fuel pump operation: Listen for the fuel pump whirring when you turn the key to the "on" position (before cranking). A weak or failing pump might struggle under heat.
The intermittent nature of the problem makes diagnosis more challenging, but the heat sensitivity strongly suggests one of the issues mentioned above. Professional diagnosis is recommended to pinpoint the exact cause.
