1GM10 Yanmar Surges, Dies, Runs After Bleed

[rkahan]

Have a Hunter 25.5 with single cylinder 1GM10 diesel. After approx 2 hours of running at 2700 RPM, get surging (decrease then increase in RPM) for a few minutes then engines dies. Then I use the lift pump lever to bleed air (noticeable) at the main filter screw and then at the injector screw, and she starts right up and runs for a few hours just fine, and starts the surging thing again. Bleed and continue on...happens a few hours later.
Background: After the first time this happened, I replaced the Racor filter and O'ring, the main cartridge filter, the fuel line from the tank to the racor, and the fuel line from the racor to the lift pump.
One other item is that the first occurrence of the surging occured approx 2 hours after I was pulled off a sandbar..the tow required the the boat to be "leaned" to starboard so far that the toe rail was hitting the water. When I changed the fuel filters, I blew through both fuel lines back to the tank (thinking they got debris in them) but they seemed clear. I have not messed with the tank vent. Nor have I tried to unscrew the pick up at the tank.

Open to suggestions as I'm preparing for a week long sailing adventure. Thank you and regards.

 

[kloudie1]

Sounds like a very small air leak on the suction side of the lift pump. banjo fitting and washers on lift pump suction .. any hose connection or gasket between the tank and the lift pump, including the tank shut-off valve stem seal.

EDIT: check the fuel tube in the tank for a screen at its tip, since this could add pressure drop which would make any small leak worse. Good Luck

 

[Benny17441]

I would venture to say that you got all the crap in the fuel tank stirred up and you have a partial blockage on the fuel tank pickup tube. As Kloudie explains that may create or exacerbate a small air leak. The surging is just the engine running out of fuel.

 

[sailaway78]

total agreement

You have a small air leak, somewhere on the suction side of the lift pump. I been there, and these can be a b---- to find. I'm not sure that it's not easier to start at the tank, and replace all the fuel line and all fittings, between the tank and the lift pump. Depends on whether you would ratherr spend the money, or crawl around pulling your hair out.

 

[Steve Dion]

If you took any fuel lines loose that have those banjo washers there is a good chance that it will leak. Those small engines only use a little fuel so it is not suprising that you can run for a while before repriming.

Check all of you hose clamps too. I would remove the filter from that you replaced and see if there are any orings/seals that are tweeked.

These are also known as crush washers.