Boat Diesel – The starter motor turns the engine but it will not start

1. Check that there is fuel in the tank and the isolator valve is open.
2.Check that the engine stop valve is open. Cable-operated valves are easy to leave in the off position. Electrically-operated valves can jam in the closed position, or the return spring may become disconnected or break.
3.Check that the fuel lift pump is working by operating it manually and that there is fuel flowing from the vent screw in the low pressure system. This is usually on the filter.
4. Check that the engine speed control – throttle – is connected and working correctly.
5.Check the high pressure piping from the high pressure pump to the injectors for leaks. Pipes can fail, fatigue cracks can develop and union nuts may work loose.
6.Check that the fuel pre-filter is not clogged, by inspection. If no pre-filter is fitted (only a water separator) then check the fine filter is not clogged by opening the bleed screws and manually operating the lift pump.
7.Check all low pressure fuel piping for leaks, especially if the tank is situated below or level with the engine.
8.The most likely cause is air in the fuel system. Bleed the fuel system of air as described in Chapter 2. (A leak in the low pressure part of the system will not necessarily be evident, as it will suck in air rather than expel fuel.) Check all connections on the low pressure side of the fuel system for tightness.

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