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Yanmar Marine Engine Help

Bleeding Air from the Fuel

Caution All engines: If the engine does not start on the first attempt, turn off the raw water cock. When the engine starts, turn on the cock immediately. Prolonged cranking with the raw water turned on will fill the engine cylinders with water!

TIP:

  • If the HAND PRIMING LEVER doesn't have any resistance through any of its travel, rotate the engine crankshaft through 360deg. Use the starter motor or crank handle..
    There is no resistance to the hand priming lever because the internal actuating arm is on the top of the cam that drives it. Rotating the engine crankshaft 360deg will turn the camshaft 180deg, the arm will now be on the back of it's cam and you should feel resistance when operating the hand priming lever.
  • Put a rag or paper towel around a loosened bleed screw or injector pipe nut to retain the diesel that will leak out.
  • Use a folded paper towel or toilet paper to check around joints for leaks. Leaking fuel will quickly be absorbed by the paper and stand out like the proverbial....
  • Clean the engine bay, or any other affected area, with a lemon scented dishwashing liquid to get rid of any diesel smell.
  • One lousy day, when you're bored and have nothing else to do, paint the heads of the bleed screws red, it will help you find them when the heart is pounding, the stomach is heaving and the scenario at the top of the HOME page is happening to you.
  • SB, YSB and YSE engines: To bleed the injector line the throttle lever must be in the full power position.

GM series engines:

Open the small BLEED SCREW on top of the engine mounted fuel filter and operate the fuel lift pump by hand. After the fuel filter has been purged of air, close the bleed screw (don't do it too tight, it's only little) and open the one on the fuel injection pump. Again, after the air has been purged, close the bleed screw. The engine should now start, if not you will have to bleed the high pressure side as follows: Crack the pipe nut at each injector, open the decompression levers and rotate the engine with the starter motor.
When the air appears to have been purged (the fuel looks clear, not whitish), tighten the nuts firmly, close the decompression levers and start the engine. Check for leaks and clean up any spilt fuel.

LH series engines:

Open the BLEED SCREW on top of the engine fuel filter. Unscrew the fuel lift pump priming handle, it will pop up. Pump the plunger down and up until no more aerated fuel comes from the filter bleed. Close the bleed screw and screw the pump plunger in firmly. Start the engine. Check for leaks and clean up any spilt fuel.

Note: The fuel injection pump is self bleeding and should not require attention unless it has been removed.

Other engine models:

- are similar to the two examples above. Some engines have a HAND PUMP on top of the fuel filter, push it up and down. You may not need to open any bleed screws as the aerated fuel is sent back through the return line to the tank.

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