Bleeding Air from your fuel lines.

Yanmar diesel generator engines use a high-pressure, direct injection fuel delivery system. Fuel is drawn into the system with the lift pump. The high-pressure fuel injector pump then pressurizes the fuel and delivers it, in precisely metered bursts, to the injectors through the fuel oil piping. Any air in the fuel system can lead to an erratic or non-running condition. Air should be bled from the fuel system whenever the fuel oil filter is changed or any of the fuel oil pipe fittings are loosened. The fuel oil filter must be primed with diesel fuel during the filter change in order for the lift pump to be able to force fuel through the system and bleed the air out.

1. Turn the fuel control valve to the “On” position. You must have fuel in the tank before beginning this process.
2. Loosen the air bleed screw on the top of the fuel filter canister if you have an external fuel filter.  Let gravity fill the fuel filter canister and displace the air.  Alternately you can remove the rubber fuel line exiting the the filter and let it bleed into a container to prevent spilling diesel fuel. Continue until fuel escaping the bleeder is free of air bubbles.
3. Follow the rubber fuel line to the fuel pump and disconnect it again bleeding until air is removed. Replace the fuel line.
4. Loosen the high pressure fuel line on the outlet side of the fuel pump and crank the engine to confirm the pump is working. Tighten and clean area when complete.
5. Loosen the high pressure fuel line at the entrance to the fuel injector and continue to bleed by turning engine over with the starter until fuel comes out at the delivery valve with no air in it. Do not over crank as you can damage the engine starter. Tighten the fuel deliver valve with a wrench. Turn the engine over with the starter until fuel comes from the injector pipe fittings with no air in it. Tighten the injector pipe fittings securely with a wrench.