jamie N
Well-Known Member
Indeed, mine was also, but it doesn't take a great decrease in compression to make it 'not enough'. I can convince myself that it 'felt good' also, but it could be wishful recall or something.
Last edited:
Rebuilt YSM-12 will not start after rebuild.
- Thread starter Gregted
- Start date
Boater Sam
Well-Known Member
And there is a world of difference between being a bit hard to turn over and creating the compression ratio of over around the minimum 22 to 1 necessary to ignite the fuel.
petemorley
New Member
Hi All,
Not much to add to all that has been said but just done a refurb on a Yanmar that wouldn't start. Clues were the new starter motor fitted prior to taking possession. Lots of turning over probably caused starter failing. Injectors and pump professionally checked first. Compression was good but only on one cyllinder. Once head removed the story became easy to diagnose. I had the same corrosion one cyllinder and valves. The blocked water / cooling channels meant overheating on that cyllinder meaning that head gasket failed letting in raw water and head needed skimming with new valves and seats to solve. The head skimming solved the warping / corrosion and it started after full bleeding.....I also recommend good battery for high speed turning and decompression to get speed up.
Hope you get it sorted.
Not much to add to all that has been said but just done a refurb on a Yanmar that wouldn't start. Clues were the new starter motor fitted prior to taking possession. Lots of turning over probably caused starter failing. Injectors and pump professionally checked first. Compression was good but only on one cyllinder. Once head removed the story became easy to diagnose. I had the same corrosion one cyllinder and valves. The blocked water / cooling channels meant overheating on that cyllinder meaning that head gasket failed letting in raw water and head needed skimming with new valves and seats to solve. The head skimming solved the warping / corrosion and it started after full bleeding.....I also recommend good battery for high speed turning and decompression to get speed up.
Hope you get it sorted.
Beneteau381
Well-Known Member
Diesel engines have different compression ratios. Some like mine are 17:1. Worn engines lose compression and become difficult to start, they start easily on ether based easy starts. So once you understand the basics of diesel engines then diagnosing correctly becomes easier.
