1GM10 - Still poorly sick

[fireball]

One thing not commented on by others was your comment about the head not fitting firmly in place and having to line it up by hand ... could it be that this is the cause of the loss of compression?

Easy way to test might be to smear soapy water around the same way as you do for tire leaks ....

Just before you go ripping it all out .... /forums/images/graemlins/wink.gif

 

[Tranona]

Re: Bent ConRod Test: (and a bit more)

Reference the con rod. The manual refers to "twist and parallelity". and "When the measured value exceeds the wear limit, replace the connecting rod. Twisting and poor parallelity will cause uneven contact of the piston and bushing and shifting of the piston rings, resulting in compression leaking".

So, I guess you have to check it if you pull the piston and rod.

 

[srp]

Re: Bent ConRod Test: (and a bit more)

[ QUOTE ]
The weakness in the 1GM10 as said many times here since this BB began is the 1GM10 starting and closing down sequences plus an appauling piece of design that allows the engine to get screwed up the next time it trys to start if the previous closing down sequence wasn't followed exactly = bm-bm-bm-suck!!!

[/ QUOTE ]
I'm learning a lot from this thread, but I'm a bit puzzled by this bit - can you explain what you mean by the 'starting and closing down sequences' you mention?

 

[mortehoe]

Starting and Stopping Engine sequences

Starting: Keep the raw water seacock closed till the engine starts. Then remember to open it at your leisure: ie within 3 minutes.

Stopping engine: Close raw water seacock. Rev engine up (in neutral) for about 20 seconds to blow all water out from the exhaust knuckle to beyond the waterlock. Drop the revs to tickover and pull the engine stop mechanism.

In the manual it says to rev the engine up to blow the gases out .... but what you need to do is to blow the water out so that it can't go backwards on the last engine gasp into the cylinder via the exhaust valve.

 

[Heckler]

on the right track, but tight tappets dont open the valves later to a material degree, what they do do is prop the valve open so that they leak the compression!!

 

[Heckler]

jools
your tappets are too tight, no clearance means valves propped open, equals leaked compression past propped open valves, just slack em off a touch till you can feel there is clearance, thats with it at top dead centre, not crucial the gap at this point to get it going as long as it isnt too enormous.
stu

 

[srp]

Re: Starting and Stopping Engine sequences

Thanks Morthoe - I must admit I've never done that on either of the two Yanmars I've had, so it sounds as though I need to change my ways.