Misfire/white smoke 8v71 on start up

[AndyyCoulic]

Its one of those threads!
My 8v71 in my 4106 is misfiring on start up for the first few minutes. putting out white smoke (unburnt fuel) and has a pulsing idle, which usually is a sign of low compression ):

So i guess i should start looking at my options for what i want to do in the future before the bus strands me somewhere.
rebuild, overhaul, or replace?

Im located in saskatchewan canada so i feel like my options up here are limited and i haven't come across too many people with the knowledge of 2 stroke diesels.

Engine still runs strong and starts just fine besides the rough idle, wondering if theres something i could do to bring that cylinder back to life without tearing into the engine.

I have no idea how much mileage is on the engine, i only have a hubometer that reads 134,000 km.




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[luvrbus]

It's not always low compression you could have a bad injector or valve setting

[AndyyCoulic]

Good to know. I am still on the learning curve with Detroit diesels. Whole different world for me!


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[lvmci]

Hi Andy, Salmon Arm, I think in Alberta is bus conversion central, you might look over there for DD knowledgeable mechanics, lvmci...

[akroyaleagle]

Have you tried:

Saskatchewan Transportation Co.
88 King St.
306-933-6734

There are also some in:

Battleford,  Frontier Coach Lines,  472  25th St,  306-937-2452
Regina,  Saskatchewan Transportation Co.,  920 ninth ave., 306-787-3362
Prince Albert,  Northern Bus Lines LTD, 517 17th st. west, 306-922-7700

[akroyaleagle]

a search for "diesel repair saskatchewan" listed several

[eagle19952]

ok....
but have you gotten the motor up to 190 degrees and put a load on it ? how long has it sat ?
could be a stuck ring.. could be the governor is just hunting...

[AndyyCoulic]

Thanks for the list, finding a 2 stroke specialist has been the harder part. Yup once warmed up it runs perfect with or without a load. Looking like its more a leaking injector. I havent driven it for about 2 weeks now. Prior to me purchasing it, it sat for around 7 months and the po had no clue what he was doing with the bus, still working out all the bugs from his lack of maintenance. Been just assuming the worst with everything on the bus. Slowly narrowing things down. 


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[TomC]

As Clifford said, it might be an injector. If there's a broken check valve spring, this would allow fuel to dribble into the cylinder causing white smoke at start up. Then because of the broken check valve spring, not enough tip pressure would be built up to create a good fuel firing pattern. First off, figure out which cylinder it is. Good Luck, TomC

[bevans6]

How cold is it at night?  If the temp drops below around 50 degrees F you can expect a minute of smoke and a rolling idle if you do a fully cold start.  I plug the block heater in for a couple of hours, that drops it to 15 - 20 seconds.  I also raise the engine speed to maybe 800 rpm by applying throttle pedal or pushing on the speed control lever if I am at the rear of the bus.  That takes it off the idle circuit, which is what is causing the rolling, and puts in on the main speed control circuit which is controlled with the weights and a different spring.

In other words it might be completely normal, as I understand these things anyway...

Brian

[Lin]

Brian raises an interesting point, and probably the first and easiest possibility to disqualify simply by starting the engine when it is warm.  If you have a block heater, that would be easy to do.  If you do not, it would seem to me that you really would want one in your neighborhood.  I would not suggest merely getting one for this test alone, but since I find one useful even in SoCal in the winter, I can't see how you would want to do without one.

Anyway, if when started warm there is no problem, you've found your answer.  If the problem persists even when started warm, it would be time to go to the next option.  Take heart-- although it is possible that there is a serious problem. most times it is way smaller than your nightmare.

[Len Silva]

When was the last time you actually drove it? 

Just beat the crap out of it for a hundred miles or more, you will either fix it or find the problem.

[lvmci]

Hi Andy, a DD mechanic once told me, "drive it ( a detroit diesel ) like your mad at it", lvmci...

[luvrbus]

He knows he has a dead cylinder driving it will not bring it back he needs to find the cause IMO

[eagle19952]

He knows he has a dead cylinder driving it will not bring it back he needs to find the cause IMO

pull the covers and short the injectors...oughta tell a lot..