If a diesel engine is stalling due to entrained air in the fuel oil system, what should you first inspect?

When a diesel engine is stalling due to entrained air in the fuel oil system, the most critical initial inspection should focus on the loose fittings in the booster fuel pump suction piping. Loose fittings can allow air to enter the fuel system, leading to air becoming entrained with the fuel.

Inspecting these fittings first is essential because even small gaps can create a significant issue, compromising the fuel delivery system and causing intermittent stalling. This leads to poor engine performance as the air bubbles disrupt fuel flow to the engine, preventing it from operating reliably.

While other components, such as fuel filters, the main fuel pump, and air pressure in the fuel tanks, are important parts of the fuel system, they are less directly connected to the immediate issue of air ingress. For instance, a clogged fuel filter can restrict flow but won't introduce air into the system, and the main fuel pump may be functioning adequately even if air is present in the system. Inspecting the source of the air intrusion, which can occur at those loose fittings, is a priority for troubleshooting the stalling issue effectively.