Diesel Engine Maintenance

Winterizing Small Diesel Engines

1. Drain crankcase and transmission and refill with fresh oil, change oil filter.
2. Close sea cock, remove salt water pick-up hose from water pump, and attach about 4 foot length of hose. Using 50/50 solution of antifreeze and water, start and flush thoroughly.
3. Drain the cooling system completely, remove water pump impeller and pack water pump with clean fuel.
4. To prevent corrosion caused by water and sediment in the fuel, drain and clean all fuel filters, change elements. Drain all fuel lines and refill with clean fuel.
5. Pull compression release and turn engine slowly with the hand crank.
6. Pour about 2 ounces of oil slowly into the suction pipe while turning engine. This will allow for a thin coat of oil on the valves and upper cylinder.
7. Release compression lever and stop turning the engine when the piston reaches top dead center on the compression stroke, so that the intake and exhaust valves are completely closed.
8. Tape the openings of the intake and exhaust manifolds with duct tape to help prevent corrosion of the upper cylinder during lay-up.
9. Scrape all rust or corrosion from exposed metal parts and surfaces. Scrub all metal surfaces with detergent and rinse thoroughly. Place a dust cover over engine. Do not leave the engine exposed to rain and sea breeze.
10. Disconnect the battery cables, remove the batteries from the boat. Clean the terminal ends and batteries with a solution of baking soda and water, and rinse thoroughly with clean water.
11. Apply a light coat of grease on the terminal end of the battery cables. Store the batteries in a cool dry place. Use a trickle charger to keep the batteries charged. Do not charge batteries near any open flame or confined area. CAUTION Wear safety goggles and rubber gloves to protect your eyes and skin. 

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Bleeding the Fuel System

This article contains helpful information for bleeding the fuel system of the Yanmar Diesel and all other small diesels as well.

Since the presence of air in the fuel system anywhere between the fuel tank and the injector will cause a "no start" or erratic running condition, always bleed the air from the system when the system is disassembled, filter is changed, or the engine has run out of fuel.

N.B. If you've changed the fuel filter, make sure you fill it with diesel fuel before you begin this procedure. If the primary fuel filter isn't full (or nearly full of diesel), no amount of pumping of the lift pump will be sufficient to pull fuel into the filter.

1. Make sure the fuel shut-off is in the "on" position.
2. Bleed the air from the fuel filter. Loosen the air bleed screw at the top of the fuel filter body and operate the manual handle of the lift pump until the air bubbles completely expel in the f uel flowing from the filter.
3. Bleed the air from the fuel return pipe. Loosen the connector bolt of the fuel return pipe installed on the fuel injector, and bleed the air by operating the manual handle of the lift pump (if there is more than one injector, bleed the one at the end of the line).
4. Bleed the air from the fuel line (line from the filter to the injector pump). Loosen the air venting screw at the injection pump and operate the manual handle of the lift pump until all of the air bubbles are out.
5. On the Yanmar "y!" series engines. Loosen the nipples at both ends of the injection pipe, place throttle in half position . Then loosen the delivery valve holder in injection pump (about 1 or 1 1/2 turns). When bubble-free fuel comes out, securely tighten the delivery valve holder, and then, after attaching the injection pipe, securely tighten the fuel pump side nipple. Now spin engine over with key and get solid fuel stream out of line, then tighten line at injector and start engine.
6. Bleed the air from the fuel injector. Loosen the nipple on the fuel injector side, set the throttle to half and the decompression lever to the decompression position, and crank engine. When no more bubbles appear in the fuel flowing from the end of the injection pipe, re-tighten the nipple.