Engine finally fires! Now troubleshooting cylinder 2 issues

February 19, 2017

VICTORY! Billabong’s Yanmar 3gm finally fires!

(Read text under video too!)

Harold, a diesel mechanic and fellow Shilshole Bay Yacht Club member, came out today and helped me troubleshoot the motor. With experience backing him we found the air leak pretty quickly. It is coming from the external fuel filter. We bypassed it straight into the mechanical fuel pump on the motor and she fired up pretty quickly. I will be disassembling that to determine if the issue is in the filter rings or in the filter housing itself.

Unfortunately we uncovered another issue after the motor was running. I lost one of the nuts from the valve case when we pulled the cover to inspect underneath it previously. This turned out to be a blessing in disguise because it allowed us to see an excessive amount of exhaust coming from the cover. Harold held a finger over it and a significant amount of pressure built. A well running system will have little to no pressure here.

So….what does that mean? Could be several things, bad head gasket, cracked head, clogged vent, worn piston rings, etc.

We started by cracking open the fuel injector inlets. A good running cylinder will cause the motor to die nearly instantly when its injector is cracked open. Cylinders 1 and 3 both died with their injectors cracked. Cylinder 2 cracked open and the motor kept running for about a minute before conking out. That ruled out a clogged vent. Time to go deeper and remove the head.

We pulled the head off with our fingers crossed that the issue was the head gasket. Head gasket looks fine. What’s next? Harold worked the cylinders up and down while checking for any scoring that could indicate a broken piston ring, the cylinders seem to be smooth and scoring free. What’s next? No visible cracks on the pistons. What’s next? We learned several things, first the issue is not immediately discernible with the cylinder/pistons. This could be good because the second is to look towards the head itself. The head could be cracked or leaking somewhere we cannot see. We already had it pulled off so I will be taking it in to be tested. Fingers crossed that the head is the problem. If not we look deeper and begin to think about pulling the motor out of the boat to mount it on an engine stand and pull it apart to get the pistons out of the cylinders and send the bunnies down that rabbit hole. First though I will get this head tested!

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