1. Fuel System Issues
* Fuel Pump Failure: The fuel pump may be weak or not delivering fuel to the engine.
* Check: Listen for the pump's humming sound when you turn the ignition key to the "on" position (not starting). If you don't hear it, the pump could be faulty.
* Fuel Filter Clogging: A clogged filter restricts fuel flow.
* Check: Replace the filter, even if it's recent.
* Fuel Pressure Regulator Malfunction: This component may be preventing proper fuel pressure.
* Check: Get fuel pressure readings.
* Injector Problems: Clogged or faulty injectors can prevent fuel from reaching the combustion chamber.
* Check: Have a fuel system inspection and injector cleaning performed.
2. Ignition System Issues
* Spark Plugs: Fouled or worn spark plugs can cause misfires or no spark at all.
* Check: Inspect and replace if needed.
* Ignition Coils: A faulty coil will not provide the spark needed for combustion.
* Check: Inspect coils for damage and test their output.
* Spark Plug Wires: Cracked or damaged wires can disrupt spark delivery.
* Check: Inspect and replace if needed.
* Timing Belt/Chain: If the timing belt or chain is broken or jumped, the engine's valves will be out of sync, preventing proper combustion.
* Check: Visually inspect the timing belt/chain. (This should be done by a qualified mechanic due to the complexity of this system).
3. Other Possible Causes
* Air Intake: A blockage in the air intake will starve the engine of air.
* Check: Inspect the air filter and intake manifold for restrictions.
* Battery: While cranking, the battery could be too weak to provide the necessary power for starting.
* Check: Test the battery voltage.
* Starter Motor: A failing starter may not be engaging the flywheel properly.
* Check: Inspect the starter for proper operation.
* ECM (Engine Control Module) Problems: A faulty ECM can prevent the engine from starting.
* Check: This usually requires advanced diagnostics from a qualified mechanic with access to diagnostic equipment.
Additional Tips:
* Check Engine Light: Look for a code in the engine control module (ECM). A code will indicate the specific problem area.
* Visual Inspection: Look for anything obvious, like loose connections, leaks, or damaged parts.
* Professional Diagnosis: If you haven't already, it's highly recommended to take your vehicle to a reputable mechanic who specializes in Toyota vehicles. They can use diagnostic tools and their expertise to pinpoint the problem.
Remember: If you're not comfortable working on your car yourself, always consult a professional. Electrical systems can be dangerous if handled improperly.
