1. Fuel System:
* Vapor Lock: This is the most likely culprit in hot weather. Heat causes fuel to vaporize in the fuel lines, creating air bubbles that prevent the fuel pump from drawing liquid fuel. This is exacerbated by a poorly ventilated gas tank or a failing fuel pump.
* Troubleshooting: Check the fuel lines for obvious signs of damage or leaks. Listen for the fuel pump whirring when you turn the key – a weak or failing pump is more prone to vapor lock. Consider adding a fuel pressure gauge to check the pressure. Make sure the gas cap is properly sealed.
* Fuel Pump: A weak fuel pump may struggle to supply enough fuel, especially when the fuel is already hot and partially vaporized. It might work fine when cold, but struggle in the heat.
* Troubleshooting: Listen for the fuel pump prime when you turn the key to the "on" position (before cranking). A weak pump might make a faint whirring sound or not prime at all. A fuel pressure gauge is again helpful here.
* Fuel Injectors: While less likely to be the primary cause of hot-weather starting problems, faulty injectors could contribute by delivering an inconsistent fuel spray. This is more of a problem if you're also experiencing other drivability issues.
* Troubleshooting: This requires more specialized tools and testing. Often involves checking injector pulse width and flow rate.
2. Ignition System:
* Ignition Coil: Heat can affect the coil's ability to generate the high voltage needed for spark. A failing coil might work fine when cold, but falter in hot weather.
* Troubleshooting: This requires a multimeter to test the coil's resistance and output voltage. A visual inspection for cracks or damage is also a good idea.
* Distributor Cap and Rotor (if applicable): These parts can degrade over time, especially in hot weather. Cracks or carbon buildup can impede spark delivery.
* Troubleshooting: Visually inspect for cracks or arcing.
* Spark Plugs and Wires: Worn spark plugs and wires can struggle to produce a reliable spark, and heat exacerbates this issue.
* Troubleshooting: Inspect for cracks, fouling, or excessive wear. Consider replacing them with new ones.
3. Other Possibilities:
* Crankshaft Position Sensor (CKP): A faulty CKP sensor can prevent the engine from starting, and heat can impact its performance.
* Mass Airflow Sensor (MAF): While less likely to directly cause hard starting, a dirty or failing MAF sensor can affect the air-fuel mixture, making starting more difficult, particularly in hot weather.
Troubleshooting Steps:
1. Check the basics: Ensure the battery is fully charged, the terminals are clean and tight, and all fuses and relays related to the fuel system and ignition are intact.
2. Listen for the fuel pump: Does it prime when you turn the key to the "on" position?
3. Visual Inspection: Inspect the fuel lines, ignition components (coil, cap, rotor, wires, plugs), and the air intake for any obvious issues.
4. Consider the age of components: Parts like the fuel pump, ignition coil, and spark plugs wear out over time. If they're original, replacement might be in order.
5. Professional Diagnosis: If you're not comfortable tackling these issues yourself, take the car to a qualified mechanic for a proper diagnosis and repair.
Remember safety first. Work on the car in a well-ventilated area, and disconnect the battery's negative terminal before working on electrical components. If you're unsure about any step, consult a repair manual or seek professional help.
