Most Likely Culprits:
* Low Engine Oil: Critically low oil can cause catastrophic damage, leading to a scratching sound as parts rub against each other. Check your oil level immediately. If it's low, don't attempt to start the engine again until you've added oil. Significant damage may already be done.
* Damaged Piston(s) or Connecting Rod(s): A scratching sound often indicates metal-on-metal contact within the engine. This could be due to a broken connecting rod, a severely scored piston, or other internal damage. This is a serious and likely expensive repair.
* Valve Train Issues: A sticking or damaged rocker arm, lifter, or camshaft lobe can also cause a scratching noise. These components are crucial for opening and closing the engine valves.
* Timing Chain or Belt Issues: Although less likely to sound like a *scratch*, a severely worn or broken timing chain or belt can cause the valves to hit the pistons, leading to internal damage and a variety of noises, potentially including a scratch.
Less Likely (but still possible):
* Starter Motor Issues: While you say it turns over, a failing starter could be contributing to the noise or preventing the engine from fully engaging.
* Ignition System Problems: Although less likely to cause a scratching sound specifically, ignition problems could prevent the engine from starting.
What to Do:
1. Check the engine oil level immediately. This is the most crucial step.
2. Do NOT attempt to start the engine again if the oil level is low. You risk causing further damage.
3. Have the vehicle towed to a qualified mechanic. Attempting to diagnose and repair this yourself is risky, particularly if there's internal engine damage. A mechanic can properly diagnose the problem with tools and specialized knowledge. Describing the scratching noise accurately will be helpful.
4. Get multiple estimates if the repair is expensive. Internal engine damage can be costly, so it's wise to compare quotes from different repair shops.
The scratching sound strongly suggests significant internal engine damage. Early intervention is key to minimizing the cost of repair. Ignoring the problem will almost certainly lead to a more extensive (and expensive) repair or even complete engine replacement.
