* Interference: The most likely culprit is that something was inadvertently damaged during the head gasket repair. This could be:
* Bent pushrods or rocker arms: These are easily bent if the valve train isn't carefully supported during head removal and installation.
* Damaged valve(s): Dropped tools or improper handling during the repair can damage valves, preventing the engine from turning freely.
* Incorrect valve timing: If the timing chain or belt was not correctly aligned after reassembly, the valves could be hitting the pistons, causing the clicking and preventing the engine from turning easily. This is a serious issue that can cause significant internal engine damage.
* Starter Issues (Less Likely, but possible): While the pulleys turning suggests the starter is engaging, there's still a chance of a starter problem. It could be:
* Starter motor malfunction: The starter might be engaging but not turning the engine over with enough force due to a faulty motor or solenoid.
* Low battery: A low battery voltage can lead to the starter clicking instead of cranking.
* Seized Engine (Worst Case): Although less likely given it ran fine after the repair, something catastrophic could have happened. This is a serious possibility if the valve timing was significantly off.
What to do:
1. Check the Battery: Make absolutely sure your battery is fully charged. A weak battery will manifest as clicking.
2. Listen Carefully to the Clicking: Is the clicking coming from the starter motor itself or from inside the engine? This can help narrow down the problem.
3. Try to Turn the Engine by Hand: Using a wrench on the crankshaft pulley (the biggest pulley at the front of the engine), try to turn the engine by hand. If it turns freely with minimal resistance, the problem is likely starter-related. If it's difficult or impossible to turn, there's likely internal engine damage, potentially from bent components or valve-to-piston contact. Caution: Use a socket appropriate for the crankshaft bolt and never apply excessive force.
4. Re-check the timing: If you (or the mechanic) performed the head gasket replacement, double-check that the timing chain or belt is correctly aligned. A poorly timed engine will not start and will likely cause significant damage. This requires consulting a repair manual specific to your 1996 Ford Windstar 3.8L engine.
5. Professional Help: Given that the engine ran fine *after* the head gasket repair, this strongly suggests something went wrong during or after that repair. It's highly recommended that you take the vehicle to a qualified mechanic. Trying to diagnose and fix this without experience could lead to further, more costly damage. The internal damage potential (bent connecting rods, damaged pistons, etc.) is considerable.
Ignoring this and trying to force start the engine will likely cause severe and expensive damage. Get it checked by a professional as soon as possible.
