If the engine holds compression well, and the fuel system is working correctly, but it still won't start, that tells us that your car's spark plugs may not be working. The spark plugs ignite the air/fuel mixture inside the engine's cylinders. It's the resulting explosion that actually powers your car.

What causes an engine to crank but not start?

When your engine cranks but won't start or run, it could mean your engine is having trouble producing a spark, getting fuel, or creating compression. The most common causes are problems in the ignition (for example, a bad ignition coil) or fuel system (for example, a clogged fuel filter).

What sensor would cause a car not to start?

A bad Crankshaft Position sensor is a common cause of no starts. The signal from this sensor goes to the PCM or ignition module that switches the ignition coil(s) on and off. If you have an RPM signal, a bad ignition module or PCM may not be switching the coil(s) on and off.