* The High-Pitched Noise: That sound is likely arcing, meaning electricity is jumping across a gap instead of following the intended path. This can be caused by:
* Worn Distributor Cap and Rotor: The cap and rotor are crucial for distributing the high-voltage spark to the spark plugs. Cracks, carbon tracking (black marks), or wear can cause arcing and misfires. Even if you've replaced the cap, ensure it's correctly seated and there's no damage. The rotor needs checking too.
* Worn or Damaged Spark Plug Wires: Similar to the cap and rotor, cracked or worn spark plug wires can lead to arcing and misfires, hindering the engine's ability to start and run smoothly.
* Failing ICM (Ignition Control Module): The ICM is the "brains" of the ignition system. If it's failing, it might not be delivering the correct voltage or timing to the distributor, resulting in the arcing and ultimately, a no-start condition. The high-pitched squeal could be a sign of the ICM's internal components failing.
* Faulty Coil: Although less likely given the cap noise, a failing ignition coil can cause weak or inconsistent spark, leading to a rough idle or no-start.
* Why it won't start now: The high-pitched noise was likely a precursor to a complete ignition system failure. The continued arcing could have damaged components, leading to a situation where no spark is now reaching the plugs.
Troubleshooting Steps:
1. Visual Inspection: Carefully examine the distributor cap and rotor for cracks, burns, or carbon tracking. Inspect the spark plug wires for damage, fraying, or cracks. Replace any damaged components.
2. Check Spark: Use a spark tester (available at most auto parts stores) to verify that you are getting a strong spark at each spark plug wire. If you're not getting a spark, the problem is likely in the ignition system (ICM, coil, or wiring).
3. Test the ICM: This requires a multimeter and some knowledge of automotive electrical systems. A failed ICM often shows a problem with its internal components when tested with a multimeter. You can usually find testing instructions online specific to your 1995 Astro's ICM. (Consider getting a professional to test it if you're not comfortable with electrical testing).
4. Check the Ignition Coil: A failing coil may not produce sufficient spark. Testing this also usually requires a multimeter.
5. Consider the Distributor itself: While less likely, the distributor's internal components could be damaged.
Important Note: Working with the ignition system involves high voltage that can cause serious injury. If you're not comfortable working with automotive electrical systems, it's best to take your Astro to a qualified mechanic. Diagnosing this issue requires systematic testing, and replacing parts without proper diagnosis can lead to wasted money.
