Combines 649T engine smoke at startup

[John]

Had a 649I in both the M2 and 7020. They both smoked and ran rough for a few seconds on start-up. I always figured that it was unburned fuel that was in the cylinders before the engine fired. Neither machine was an instant starter and had a couple cranks to put fuel in and not burn it.

 

[tbran]

yup, only do this extra test before assuming just a quirk of a relatively low compression engine. Hold the hand above the exhaust and check for water in the initial startup flow. Have seen electrolysis or leaky head gasket allow water on top of piston which keeps these cyls from firing intitially. This would be a symptom of more bad things to follow..

 

[Turbo]

Could need head and rotor in injection pump.May not hold fuel in head and rotor and has to crank a few more revs before startup.This will make it sound like running on four,then five,then finally all six.

 

[Walt]

Thanks for the responses. It seems to start slowly, running on just a few cylinders for about 5-10 sec, with black smoke coming out the exhaust, then it begins to fire on all and the black smoke turns to white, then goes away in a couple of minutes. After that when turned off it starts right back up with no smoke or missing even after it has been setting a couple hours, takes at least a day of setting before the black_white smoke happens again. Just got the combine over the summer and did not know how it ran before damage to valves and pistons. Put new head gaskets in during repair. I will check for moisture upon start up. Any additional ideas or comments most appreciated. Walt

 

[Rig]

In my opinion, this is nothing unusual. Cold startup with these engines is terrible. They are absolutely addicted to ether in cold weather. If you ground the valves you might have lowered the compression some. I have yet to figure out what makes AC engines so cold-blooded. I think it is MandW that makes pistons for this engine with the top ring almost at the top of the piston instead of ~ an inch down to improve cold starting. I don't know how well they work. Considering them on chore tractor.

 

[tbran]

yes but this would involve a fuel restriction as the pump is lower than the fuel pump most of the time. The vacuum would cause this problem you describe.

 

[Ilnewholland]

I have the MandW pistons in a 7060 and it is the hardest starting tractor I have on the farm. It will smoke and run rough when it starts, but has a lot of power when warmed up. I just always plug the block heater in when below 40 degrees.