Originally Posted by bsurvey
you melted the o rings that seat the injectors and are dumping raw fule into the chamber along with excess air
There are no o-rings in the yanmar 3gm
injectors, just shims and springs. Same really with the injector pump
. The only oring on the pump is sealing the top part nut to the injector body and probably would not cause the smoking.
Here's a test, with the engine idling, pull each decompression lever one at the time and see if the black smoke changes to grey or goes away. If it changes you know that the problem is one injector assembly.
I'm pondering if one or more springs that control the governor tension changed temper and got a little weak.
That the engine starts right up means timing and compression
Hum another test.
Remove the acorn cap over the injector limiter, on the front of the engine. Mark with a black marker the position of the injector limitor stud to the case. Now loosen the lock nut (big nut against the cover, not the small nut at the end of the stud), and turn the injector limiter 1/4 turn clockwise, tighten the long nut and start the engine and see if the smoke is better. If better, repeat 1/4 turn adjustment till smoke is gone.
Note: improper adjustment of the injector limiter can damage the engine. But as your already have excessive smoke, that to me means your getting too much fuel to the cylinders. The injector limiter adjusts that.
If no change is noted, return the injector limiter to the original mark and retighten the lock nut and acorn nut.
It's possible the little roller bearing plate between the governer and crankshaft, lost
it's bearings, which would cause excessive fuel input. All that and the springs are access by removing the timing cover, which is easy after the crank pulley is removed, which is not easy. If one of the springs on the governor, lost
temper that would cause black smoke too. Adjusting the injector limitor would adjust the temper loss out.