Yanmar 1gm10 compression test

[Guest]

Please could any one tell me the compression presure to be expected on a 10 year old 1gm10 engine. after having to replace the head last year due to slight hole in casting (water jacket)above exhaust valve the engine has been running ok but seems to be reluctant to start when cold once started it runs fine until the next day, I am wondering if the con rod may be slighly bent lowering the compression, also is there anyway I can check the piston height through the injector hole and if so what should it be ? I don`t really want to remove the head again but it may be the easiest way, if so how high should the piston be in relation to the block surface. thanks

 

[Guest]

Mechanics have a proper compression gauge for diesels. Correct would be greater than 300#. They remove the injector, replace it with the gauge, crank it over and read it. Takes less than 1/2 Hr total time. If you read less than 300#, consider a new head gasket. BTW, did you machine the head and re-torque it at 50 hours as recommended? Cliff Moore, SV Pelorus, USA

 

[Guest]

Thanks Cliff. the head was new and it was re-torqued at about 50 hours

 

[Guest]

My 1GH10 was down to 190psi after fourteen years. The Yanmar agent that I used has come across several engines of my vintage with a problem in the exhaust manifold. This eventually causes water to enter the cylinder. My eventual re-build bill is breath taking. I shall be removing the new manifold once a season in future to check. I do have the max and min compression values on the boat. If you still need them, email me and I will be happy to supply them. If in a hurry, ring EP Barrus - assuming you are in the UK??

 

[Guest]

yes Pete ..use a piece of soft fuse wire or solder inserted into the cylinder thro' the injector hole ... turn thro' T. D.C then measure thickness (0.7mm, 0.0276ins)

I can send you the relevant page of the workshop manual if you want

 

[Guest]

before you look for difficult problems, check the tappet settings. on a new head, they will settle down a bit and this could lead to valves not seating properly and low compression. the injection system has an anti drain back arrangement (apparently). if fuel is draining back, this could contribute to the engine needing a few turns before it starts after having been stood for a while. for advice from a good mechanic, contact cellar marine, porthallow cornwall. no connection other than satisfied customer.

 

[Guest]

Thanks for all your good advice

NM