By Larry Carley
Technical Editor

In today’s world of high-tech electronics, onboard diagnostics and scan tools, you would think engine diagnostics would be easier than ever. Yet some technicians struggle when confronted with an engine that cranks, but refuses to start. Most no-starts do not generate any fault codes, so how do you proceed to find out what’s causing the problem?

For any engine to start, three things are necessary: fuel, compression and spark. If any of these components is lacking, the engine won’t start.

NO FUEL, NOT ENOUGH OR TOO MUCH?
The fuel system must be generating normal fuel pressure, and the air/fuel ratio must be correct for the ambient temperature and engine temperature. If the air/fuel mixture is too lean, it won’t ignite and the engine won’t start. If the air/fuel mixture is too rich, it can flood the engine and also prevent it from starting.

No fuel pressure is one of the most common causes of no-starts o...