What should be done first to find the cause of a misfire on a diesel engine?

• A. Check glow plugs
• B. Check fuel pressure
• C. Inspect spark or power supply
• D. Identify the misfiring cylinder

Answer: (D)

Finding the exact cylinder that isn’t delivering power is the first move. In a diesel engine there’s no spark to inspect like in a gasoline engine, so you don’t start by checking ignition components. Once you’ve identified which cylinder is misfiring, you can focus the investigation on that cylinder’s fuel delivery and compression—injector performance, cylinder compression, and, if cold starting is involved, the glow plug for that cylinder. This targeted approach lets you distinguish between problems that affect one cylinder (which you diagnose with cylinder-specific tests) and issues that affect the whole engine (which would require broader checks). Tools such as a misfire counter or a cylinder balance test, combined with compression and injector tests, guide you to the actual cause efficiently.