Crank But No Start

Common causes are missing fuel, missing spark or an immobiliser block. A faulty crankshaft position sensor can stop both injection and ignition. Low compression can also cause it. Live data showing engine speed while cranking quickly tells whether the crankshaft sensor is working. A security light that flashes during cranking suggests the immobiliser is blocking the start.

Diagnosis checks fuel pressure, spark, injector signals and immobiliser status step by step.

Long cranking can overheat the starter and drain the battery. On petrol engines, unburnt fuel can flood the engine and catalytic converter.