Yanmar 186D - hard to start

[DawsonAcres]

Also in NorCal, an hour north of SF, and a YM186D. This tractor starts easily in our climate and likely would without using the thermostart at all. After 15 seconds of thermostart it fires instantly or within a couple revolutions of the crankshaft. But it does smoke when it hasn't run for a while. My theory is like an old car, there is oil running down the valve stems when it sits.

I suspect you are running the thermostart far too long and it may be warm but not igniting the dripped fuel. So all that black smoke is the dribbled fuel from the thermostart.

Yanmar's manuals - and my experience - (that's my YM240 thermostart photo in the Hoye description) - say the thermostart flame ignites with an audible pop, or poof, after 15 seconds. You might need to remove the air filter element to hear it on this model. I would investigate that, next.

With no glow plugs, testing compression is a major project on these. Getting the injectors out then back in and sealed completely is nearly a pro mechanic project. And needs a $100 tool to get the injectors out in condition they can be re-used, at least on my similar YM240. Then the cost of the compression tester. If you can feel compression resistance while it cranks I wouldn't worry about compression yet.

You are spinning it with compression released, then dropping the release lever after it's spinning, no?

Thermostarts are cheap, under $20 on Ebay. There's only one version regardless of description. But some include a screw for the wire while all accept a slide-on connector. Its trivial to install. I would replace that as the next effort.

And finally, Don't use Starting Fluid like they use on large diesels!!!

Thanks, this is all helpful info. I am also an hour north of SF. Maybe these two old 186D are neighbors?
Yes I have tried using the compression release and it doesn’t seem to make much difference. I will try using the thermostart for shorter duration as suggested as well as pulling the intake to see if I am actually getting a flame.

 

[ponytug]

Thanks, this is all helpful info. I am also an hour north of SF. Maybe these two old 186D are neighbors?
Yes I have tried using the compression release and it doesn’t seem to make much difference. I will try using the thermostart for shorter duration as suggested as well as pulling the intake to see if I am actually getting a flame.

I'm kind of surprised that the compression release doesn't make much difference. I find the effect of getting oil up into the engine and getting the rpm's up significant for most engines that have compression release.

I hope that you can get a look at your thermostart to see how it is doing.

Good luck!

All the best,

Peter

 

[NHYanmar]

I own the identical tractor and initially experienced difficult black smoky cold starts below 40 degrees, like you have been. I removed the rocker arm cover and adjusted the intake and exhaust valve clearances. They were all too tight, one exhaust valve was barely closing ...the gaps close up from normal engine usage and wear. I believe the gap is .006 inches, but don't quote me on that. There might be a sticker on the rocker arm cover, stating the gap clearance. The valve cover gasket is reuseable if you are gentle with it. I think its a rubber sealing ring, I adjusted the valves 6 years ago. Huge improvement on cold startups. 15 seconds max with key turned counterclockwise for thermostart. throttle lever set at full throttle. crank and engine should catch within 3-5 seconds. then lower the throttle to 1000 rpm. my tractor will start at 5 degrees F in a unheated barn, provided the battery is properly charged. Before I adjusted the valve clearances, the tractor would start fine when warm outside, 60 degrees plus, but struggled when outdoor temps were lower.

 

[bmaverick]

Yanmar's manuals - and my experience - (that's my YM240 thermostart photo in the Hoye description) - say the thermostart flame ignites with an audible pop, or poof, after 15 seconds.

Mine doesn't do the pop or poof. It does a a faint click noise and sizzle like beef on the grill.

 

[DawsonAcres]

Ok quick update: After listening to all the comments about starting process I retried the following:
-only 10-15 seconds on the thermostart
-throttle wide open
-compression release

This alone seemed to make a big difference. I was able to start it pretty easily and there was a lot less smoke. I think I was dumping a lot of unburned fuel by holding the thermostart for 45 seconds. I bought a new thermostart and will test the old one when I replace it to confirm my suspicion that it isn’t igniting.

I also plan to adjust the valves. Will report back just to close the loop on this thread. Thanks everyone.