Ignition System Issues:
* Distributor cap and rotor: Even a slight misalignment or worn components can disrupt spark delivery. Replacing these with new parts during a tune-up is standard practice, and improper installation is a common cause of no-start. Double-check for correct placement and secure connections.
* Spark plugs: While new plugs are beneficial, incorrect gap setting, improper threading, or cross-threading can prevent proper sparking. Check the gap using a feeler gauge and ensure plugs are tightened correctly.
* Ignition coil: A faulty coil won't produce sufficient voltage for sparking. This is less likely if it was running fine before. However, the tune-up process might have inadvertently damaged it (though less likely than other problems).
* Ignition wires: Worn, damaged, or incorrectly routed wires can lead to misfires or no spark. Make sure each wire is firmly connected to both the distributor and the spark plug and that there are no cracks or damage to the insulation.
* Distributor: Internal issues within the distributor itself (worn points in older systems or electronic issues in later models) can prevent proper spark delivery.
Fuel System Issues:
* Fuel pump: While less likely, the tune-up process might have inadvertently damaged a fuel line or disrupted the pump's operation. Check for fuel pressure using a gauge.
* Fuel filter: A clogged fuel filter, even if it wasn't part of the tune-up, can prevent fuel from reaching the engine.
* Carburetor (if applicable): If your Ranger has a carburetor, improper adjustment during the tune-up (if you adjusted it) could lead to a lean or rich condition preventing starting. A simple rebuild or cleaning might resolve this if it was messed with.
Other Potential Problems:
* Vacuum leaks: Disconnecting and reconnecting vacuum lines during the tune-up could introduce leaks that disrupt engine operation. Carefully inspect all vacuum lines and connections.
* Timing: While you say the firing order is correct, the distributor timing might be off. A slightly off timing could prevent proper combustion.
* Sensor issues (if applicable): Depending on the specific engine, certain sensors (like a crankshaft position sensor or other electronic components) are critical for starting. A sensor malfunction may have been aggravated or inadvertently damaged during the tune-up.
Troubleshooting Steps:
1. Check for spark: Use an inline spark tester on each spark plug wire to confirm you're getting spark. This is the most crucial step.
2. Check for fuel: Verify fuel is reaching the engine. Look for fuel in the fuel rail (if fuel injected), check the fuel pump for sound when you turn the key, or smell for fuel at the carburetor (if applicable).
3. Inspect vacuum lines: Check all vacuum lines for proper connection and leaks.
4. Recheck ignition components: Carefully examine all ignition components (wires, cap, rotor, coil) for damage or improper installation.
5. Verify timing (if possible): If you're comfortable with it, double-check the distributor timing.
If you're not comfortable working on the ignition system, it's best to take the Ranger to a qualified mechanic to diagnose and repair the problem. Improper repairs can cause further damage.
