BoatHowTo · video

What this video covers

A marine diesel engine that intermittently dies underway is almost always losing fuel to an air leak, and Nigel Calder walks through a systematic method to locate it. The fuel system divides into two zones at the lift pump: the suction side (tank to lift pump) and the pressure side (lift pump through injection pump to injectors). To test the suction side, splice a short length of clear PVC hose between the tank and the lift pump, run the engine, and watch for bubbles.1:08 If the suction side is clean, the pressure side is the more likely culprit — specifically the injector leak-off pipes, which typically return to the secondary filter before looping back to the tank.1:30 Disconnecting those pipes from the secondary filter and routing them directly to the tank often eliminates that path.1:51 One prior check overrides all of this: if the problem started immediately after a filter change, a mis-seated O-ring or undertightened filter housing is the first thing to inspect.1:56

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