Tune-up (run a rack) 83 6v92ta

[Busnut83]

Opinions needed My bus starts great,,, runs good 65-72 on flat or downgrade,,, when pulling a grade it will drop to 45-35 mph,,, smokes if I keep the petal to the floor,,, if I back off a quarter-inch the black smoke stops???  I get about 6.5 mpg...  Is this normal for a njt-mc-9...
   The detroit diesel co in Dallas,tx says it needs a tune-up,,,, this is my 3rd year running it (15000 mi )...

estimates 7-9hr labor at $102 hr.  I hate to spend the money if its not needed ??

Thanks again

ps I replaced the 2 radiators and no more overheating...

ps The engine compartment reaches 280* ? could it just need some cooler air ?  at night she runs a lot better....

[Buffalo SpaceShip]

Sounds normal to me. The black smoke is just telling you to take your foot out of it (and then you do), because there's only so much fuel that can be delivered to a diesel under any given load. It converts what it can to HP and the rest just goes out the tailpipe, but first washes down the cylinders and heats up your engine.

It's good practice to climb hills on partial throttle and avoid lugging the engine at all costs. Downshift the manual AND auto trannies, and try to keep the revs between 1700-1900rpm, according to the bus-sage, RJ Long.

You might consider "aerating" your engine compt. with louvers, screens, etc.  All of the modern coaches have a LOT of ventilation in the back caps, so it seems like a smart thing to do to an older rig, too. My aftermarket cap on my Buff has a large opening it it, and I can feel the heat radiating out of there after I stop.

HTH,
Brian Brown
Longmont, CO
4108-216

[TomC]

Try pulling one of the valve covers to see if you have 90 injectors.  Then see if you can see the number cast into the turbo.  With the turbo, the engine should NOT smoke even under full pedal.  What it sounds like is that the injectors are bigger without the turbo being matched up.  It could also be something simple like a dirty air cleaner.  Whenever the engine is smoking, it creates excessive internal heat that can crack heads or overheat the pistons and in the worst scenario, could cause something to come apart.  Considering an engine overhaul is around $10,000, how expensive is $800?  Then you can pull the hills faster since the engine will be adjusted properly and no smoking. Good Luck, TomC

[ndbusnut]

Diesels need lots of air. The first thing to do is replace the air cleaner. You might be surprised how much it will help.