Several factors could cause your 1AZ-FSE engine to crank but not start, despite having fuel and only a spark. Here are a few possibilities to consider:
- Incorrect Timing: Verify if the timing belt/chain is correctly aligned, ensuring proper synchronization between the crankshaft and camshaft. Misaligned timing can disrupt ignition timing and prevent the engine from starting.
- Faulty Ignition System: Check the spark plug wires or ignition coils to ensure they are in good condition and delivering sufficient spark to the spark plugs. Replace any worn or damaged components as needed.
- Fuel Pressure Issues: Check the fuel pressure to ensure the engine is receiving adequate fuel pressure to operate. A low fuel pressure could result from a faulty fuel pump, clogged fuel filter, or other fuel system issues.
- Faulty Engine Sensors: Inspect various sensors, such as the crankshaft position sensor or camshaft position sensor, which play crucial roles in providing information to the engine control unit (ECU) for proper ignition timing and fuel injection. A malfunctioning sensor could disrupt engine operation.
- ECU Issues: The ECU controls the engine's various systems, including ignition and fuel injection. A malfunctioning ECU could result in incorrect signals to the ignition system, leading to starting problems.
- Mechanical Issues: Check for mechanical problems, such as worn or damaged piston rings, cylinder bores, or valves. Compression loss due to these issues can prevent the engine from generating enough power to start.
If you have checked these factors and are still unable to diagnose the problem, it's recommended to seek assistance from a qualified mechanic or visit an authorized Toyota dealership to ensure proper diagnosis and repair of your vehicle's engine issues.
