Yanmar 3gm30f lifespan and rebuild options.

[skipperpete]

Originally Posted by Mg451

So I ordered a compression tester with an adapter that supposedly Is for a 3gm30f. I haven't pulled out the injectors yet but it looks like the injector cone out and then there is a precombustion chamber and heat shield and some gaskets that aren't all one particular the injector. When I insert the adapter do need to put in these parts..I assume I just need the gasket? I haven't actually pulled it yet so maybe it'll be overwhelmingly obvious when I do but I'm trying to get all the parts in dance that I'll need.

Yeah, just be careful ya dont blow out the top half of the precom chamber, best to leave the other cylinder injectors in place and remove/re fit as you do the tests. Really important to have clearance on all valves, not necessarily the correct clearance…. But just not tight. The wet compression test takes a bit of care and is often misleading, if you put a shot of oil in a little GM cylinder of course the compression will increase just because of the volume of the oil alone and it might not be because of the rings being sealed by the oil… there’s precious little volume remaining in the cylinder at TDC …nearly all is in the precom chamber. On bigger engines the oil never really gets to the rings, it sits in the piston crown cavity and gets blown out on the first or second compression.
Hope you get some good numbers!