The operator of a diesel truck has a complaint of low power and no smoke. the technician should first check the

• A. Air filter for restriction
• B. Fuel filter for restriction
• C. Exhaust pipe restrictions
• D. Turbocharger for boost

Answer: (B)

When a diesel truck shows low power but no smoke, the first thing to inspect is the fuel delivery path. A clogged fuel filter can restrict fuel flow to the injection pump and injectors, causing the engine to lose power under load because there isn’t enough fuel to maintain proper combustion. Because there’s less fuel burning, you often don’t see exhaust smoke, which matches the symptoms described.

Other potential causes exist—an air-filter restriction could lean the mixture and affect power, exhaust restrictions would create back pressure with other noticeable symptoms, and a turbocharger issue would cut boost and change how the engine feels under load. However, the fuel filter is the most likely and quickest thing to check first to explain low power with no smoke.