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Author Topic: black smoke after up to temp on expredway  (Read 2465 times)
Dlsnow
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« on: October 15, 2013, 12:42:19 PM »

Driving down I39 about 250 miles into my trip bus started blowing black exhaust and lost a lot of power.  At 50mph 3rd barely pushes the bus on flat ground.
Temp gauge shows about 175
Outside temp is probably 60
I shut the bus off for about 10 min and started back up and it'll be fine for 30 or 50 miles.  This has happened 4 times today.

Checked coolant and oil levels and they are fine.

I have experienced a blown injector tip (constantly dumping fuel) and that blew a lot of black smoke, it is not that bad but I suspect it is fuel injector related.

Any thoughts?

Mci-7 8v71
« Last Edit: October 15, 2013, 12:45:10 PM by Dlsnow » Logged

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robertglines1
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« Reply #1 on: October 15, 2013, 03:13:37 PM »

Air blockage;  filter--rag in intake----flapper---   low air or to much fuel=black smoke  got to have correct mix.
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« Reply #2 on: October 15, 2013, 04:33:25 PM »

When you shut it down, do you have to wait 10 minutes for it to come back to normal?  What happens if you shut it down and start it right up again?
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Dlsnow
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« Reply #3 on: October 15, 2013, 04:46:30 PM »

I did shut it down while coasting downhill - probably for 1 minute and when i started it back up it was fine for a few minutes but then - black smoke.

I am at a rest stop for the night.

I do remember that when I hit the emergency flap once it blew alot of black smoke - so it makes sense it would be air intake.

At this point I can inspect the air intake system
I did replace the 4 air filters about 1 year ago
If i understand correctly the blower with the helical gears sucks air in through the air filters

Not sure what else to inspect other than the cleanliness of the air filters.
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« Reply #4 on: October 15, 2013, 04:58:03 PM »

Just pull the hose off the air horn to the filters it won't hurt it to run a few miles without the filters if it doesn't blow black smoke then it is the filters

 I take that has been converted from oil to dry filters ? when you say 4 sad you see that setup that is pour setup in my opinion  

I have a friend on this board the PO of his bus stuffed a dry paper filter into his oil bath housing now he has a dusted engine that needs rebuilding
« Last Edit: October 15, 2013, 05:39:56 PM by luvrbus » Logged

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« Reply #5 on: October 15, 2013, 05:02:14 PM »

The blower does indeed suck air in, and can mask a number of ills.  It quite mechanically pulls a certain amount of air in against sometimes quite high resistance, and can suck very hard indeed to accomplish that task.  Black smoke is lack of air, or excess of fuel, and lack of air is easiest to check out - air filter, rags sucked in, critters, take the top off the blower and look in, even run it with the top off or the air filter disconnected for a few miles to see what it does.  Check that the air box covers are all on and tight on the side of the block.  The stopping and it runs ok for a while has me buffaloed.

Clifford had the same idea, running with the air filter off...   Shocked    Grin

Brian
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« Reply #6 on: October 15, 2013, 05:21:33 PM »

Also check the integrity of the intake ducts. Could one be collapsing?
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Dlsnow
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« Reply #7 on: October 16, 2013, 05:49:13 AM »

All of the air box screws took about a 1/4 turn with some taking 1/2 or 1 full turn.

I removed the 4 air filters.

I am hitting the road now and will have an update after I pass st. Louis and the bus warms up.

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« Reply #8 on: October 16, 2013, 05:55:26 AM »

Could it possibly be related to the Turbo locking up?


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« Reply #9 on: October 16, 2013, 07:27:13 AM »

What direction are you headed?

Sounds to me like an air supply issue to me. But then again, I am not a meckenic by any stretch Grin
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Dlsnow
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« Reply #10 on: October 16, 2013, 07:35:20 AM »

Headed to Tucson / Yuma for winter Wink
At the moment I am between St. Louis and Tulsa.

Bus is driving fine for now but as you know it takes a while to get up to full temp.

I have an 8v71N  (no turbo) if I understand correctly for the 1972 MCI MC-7
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« Reply #11 on: October 16, 2013, 09:36:32 AM »

Hi;
   I too have a MC-7.  I lost a throw out bearing in the same area
   you are in. When you get to Tulsa, contact Bill Rose of Pacesetter Coach.
   Bill was most helpful.  He runs a charter company, but he also works on
   privet coaches and used to run MC-7's in his business.

                  Bill Rose   800/487-4114

    It has been a few ago and I hope he has not retired.

                        Good luck,   Merle.








Headed to Tucson / Yuma for winter Wink
At the moment I am between St. Louis and Tulsa.

Bus is driving fine for now but as you know it takes a while to get up to full temp.

I have an 8v71N  (no turbo) if I understand correctly for the 1972 MCI MC-7
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thomasinnv
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« Reply #12 on: October 16, 2013, 02:14:45 PM »


I have a friend on this board the PO of his bus stuffed a dry paper filter into his oil bath housing now he has a dusted engine that needs rebuilding

Hey clifford I would still like to take you up on the use of your shop and your expertise if its still available. Been trying to get there for 2 years now but the stars just haven't aligned. The last year was especially rough but its looking up now.

Sure glad you're back home and feeling better. The world is a better place with you in it.

Sent from my PantechP9070 using Tapatalk 4 Beta
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Dlsnow
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« Reply #13 on: October 16, 2013, 07:44:21 PM »

Well removing the air filter seemed to clear the issue right up.  The filters are pretty blackened on the intake side and there was plenty or random debris like leaves, sticks, pebbles and other dirt dust in the little catch pan at the bottom of the filter housing. 

I was able to source 1 new filter.  The other 3 are 60 miles in the direction I am heading.

Hopefully when I put the new filters I'm things continue to go well.

Also there was notably more power without the air filters in.  It usually blows a little black smoke when going up a steep hill but none today.
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Scott Crosby
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« Reply #14 on: October 17, 2013, 01:21:19 AM »

You are running your bus with no air filters in?  That's a fast way to dust the engine and trash your linings in a hurry from what I've been told.   I would not reccomend that at all. 
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