Have a 1995 , 4.6 l cougar rx7, client changed plugs drive it same day parked it next day. The day after that wont start. Getn fuel, spark, compression. Now some1 told me to change crankshaft position sensor, did that still nothing. Turns over but will not start? Any help out there?
If it has fuel, spark and compression, the only thing left is timing. Did you confirm that the fuel is gasoline and check the fuel pressure? I knew someone who poured antifreeze into a gas can, forgot what he had in there and poured it into his tank.
If the catalytic converter is clogged, air can’t enter the engine which can cause a no start condition.
When the substrate within the converter melts either the platinum-palladium coating or the aluminum oxide honeycomb material, it forms an impenetrable slag, which blocks off the exhaust flow, clogging the passages. This creates a severe back pressure that affects engine performance. A clogged converter can cause rough idle, engine hesitation upon acceleration, weakened power, hard-starting and, in some cases, a no-start condition. Faulty components that cause overly rich fuel-air mixture, like cracked distributor caps, faulty EGR valves, incorrect timing or dirty fuel injectors can all cause melting. This symptom can be diagnosed by using a vacuum gauge on the intake manifold, or an exhaust back-pressure pressure gauge before and after the converter.
Try spraying some starter fluid into the intake and see what happens then. If that doesn’t get a reaction from the engine I would then check the ignition timing.
I suspect despite ur claims that one or more of spark fuel compression or timing is missing. Timng chain or belt system possible but less likely
Why did they change the plugs, was it running fine prior to that?