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Author Topic: Smoking 8V92TA DDEC II  (Read 5736 times)
Sam 4106
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« on: August 01, 2012, 08:13:04 AM »

My ECM on my 8V92TA DDEC II was replaced in June. Since then the engine smokes on acceleration, either with a very light touch or the pedal to the floor.  With the old ECM you couldn't make it smoke. Is there a way to program the ECM to stop the smoke? I was told that the reconditioned ECM is the latest version so i'm guessing it is different from the original. I took the bus to Interstate Detroit Diesel in Fargo, ND yesterday to have the engine checked and the technician said, after hooking up his diagnostic computer and a test drive that the smoke on acceleration is normal. He has 32 years working on DD engines so he should know them well. Anyone have thoughts on this?

Thanks, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
Hard Headed Ken
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« Reply #1 on: August 01, 2012, 08:52:47 AM »

I'm guessing it's black smoke. It could be that with the latest software in the ECM the boost pressure sensor should have been changed to the newer style and I think there's more than one of those. I think Jim Sheppard had a related problem with the wrong pressure sensor, except he wasn't getting enough fuel. I hear that the series 60 folks install the old style DDEC II sensor for more power.

Ken
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luvrbus
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« Reply #2 on: August 01, 2012, 08:55:11 AM »

That's not normal for a DDEC Sam they burn clean you probably have a lazy turbo or the boost sensor is going bad is the HP setting the same as the old ECM  woops Ken had already posted sorry

good luck
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Hard Headed Ken
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« Reply #3 on: August 01, 2012, 09:04:07 AM »

That's not normal for a DDEC Sam they burn clean you probably have a lazy turbo or the boost sensor is going bad is the HP setting the same as the old ECM  woops Ken had already posted sorry

good luck

My DDEC II 8v92 didn't black smoke at all, it was 475 HP. At night I could see maybe a little haze out the exhaust if someone were behind me. The other things Clifford mentioned are good possibilities too.

Ken
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rv_safetyman
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« Reply #4 on: August 01, 2012, 11:18:15 AM »

On the Series 60 there are at least two manifold pressure sensors.  On my original 60 Series 60, they used a GM MAP sensor (max pressure was about 25 PSI - not sure).  On the second engine, they used their own and it has a max of 40 PSI as I recall.  The DDEC uses a voltage from the sensor to determine fueling.  I think that voltage is 5V max and is proportional to the boost.  So, if the boost sensor and software do not match, the ECM will not fuel correctly.  I tried to use my old software/ECM with the new engine and the voltage from the DD pressure sensor was telling the ECM that the boost was something like 14 PSI when it was really 20PSI  - thus not enough fuel and no power.  The problem was dramatic, and I don't think that is the issue here.

DD should have downloaded the program from your old ECM and then installed it in your new ECM.  If your problem occurred right after the switch, it is obvious that they did not get your new ECM programmed correctly.  If the problem was not immediate, then we need to look at the issue further.

I think there is a possibility that DD might have your original software in their main computer (by engine serial number).  A good DD mechanic could compare the two programs and tell you if the new one is programmed correctly.  If your original ECM had the software changed (more HP for example), then there could be a problem.  If it was done by a DD facility, then the upgraded software should be on the main DD computer.  If it was done by a "backdoor" modification, then there is no way to get the software back unless you have the old ECM (doubtful).

Jim
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Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
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Sam 4106
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« Reply #5 on: August 01, 2012, 01:56:15 PM »

Thanks for the responses. The program was downloaded from the old ECM to the reconditioned one at Interstate Detroit Diesel in Sioux Falls, SD so the program should be the same. Horsepower was 450 before the change and I don't think it was increased. Yesterday, the technician at Interstate Detroit Diesel in Fargo, ND, mentioned the boost sensor as a possibility  but ruled it out when he drove on the test drive and watched the computer screen. He also mentioned the injector response time being normal. This is all new to me, which is why I'm asking for help. Where would you suggest I take the issue from here? Should I ask to have the program checked to verify it matches the program removed from the old ECM? Again, any help is appreciated.

Thanks, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
Hard Headed Ken
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« Reply #6 on: August 01, 2012, 02:39:11 PM »

If you have a boost gauge and pyometers are  the readings about the same as they were?? As Clifford pointed out you maybe losing a Turbo. If I remember  correctly boost pressure should be about 26 lbs under full load.
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« Reply #7 on: August 01, 2012, 02:39:23 PM »

sorry triple post???
« Last Edit: August 01, 2012, 02:42:03 PM by Hard Headed Ken » Logged

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« Reply #8 on: August 01, 2012, 02:39:47 PM »

sorry triple post???
« Last Edit: August 01, 2012, 02:42:45 PM by Hard Headed Ken » Logged

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Sam 4106
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« Reply #9 on: August 01, 2012, 03:16:45 PM »

Hi Ken,

Thanks for your help. I don't have either turbo boost or pyrometer gauges. I talked to the service writer and have an appointment for 7:00 AM tomorrow for further testing. Hopefully they will determine what is wrong and fix it. Now that I know that smoking isn't normal I will be a little more persistent in getting a solution. I filled with fuel after leaving the shop yesterday and now know that I got the worst MPG since owing the bus, 5.15 MPG. I already knew that black smoke equals wasted fuel.

Thanks again, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
luvrbus
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« Reply #10 on: August 01, 2012, 03:28:22 PM »

Sam,  it maybe a simple as a exhaust leak also, response time does not mean much if a injector is bad why didn't he cut out 1 injector at a time and check the smoke ? or did he 

They have a bypass on the blower I am not saying it has never been serviced but they are forgotten and stick open 

good luck
« Last Edit: August 01, 2012, 04:00:31 PM by luvrbus » Logged

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Sam 4106
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« Reply #11 on: August 01, 2012, 06:00:11 PM »

Hi luvrbus,

Thanks for your help.  There doesn't seem to be an exhaust leak. The power seems to be the same as before.  I think a n exhaust leak ahead of the turbo would cause a lose of power. I don't think he cut off each injector, one at a time and there is no noticeable miss. I will ask about the blower bypass being stuck open. Will the blower bypass being stuck open cause a lose of power too, besides smoking? I have no idea if the blower bypass has ever been serviced, I know that it has not in the about 17,000 miles I have owned the bus.
 
The engine only has 95,232 miles on it since new. The engine and transmission were both put in new when the bus was converted in the early to mid 1990s. I don't have much information about the bus since we bought it from the widow of the man that converted it. I wish I did have a better history of the bus.

Thanks for your help, it is greatly appreciated. Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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Jim Shepherd


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« Reply #12 on: August 01, 2012, 06:41:20 PM »

Repeating myself, did the smoking start right after the ECM change?

If there was a delay in the smoking problem, that points less to the ECM and more towards something else.

On the Series 60 there is a restrictor in the fuel return line.  If the 8V92 has that, is there a chance it is plugged?

Jim
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Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
Blog:  http://rvsafetyman.blogspot.com/
buswarrior
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« Reply #13 on: August 01, 2012, 08:48:14 PM »

Being the simple fellow that I like to think I am...

I'm always fond of going looking for leaking intake piping, on the pressure side. One loose hose clamp on any of those connections and you've got black smoke, and often a loss of power.

Anything that steals pressure after the turbo shows as black smoke.

happy coaching!
buswarrior
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Sam 4106
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« Reply #14 on: August 02, 2012, 04:03:03 AM »

I don't think the black smoke started right after the ECM change, but not long after. At that time I was more concerned about whether the throttle problem was fixed and wasn't watching the exhaust closely. When at the shop Tuesday there were no codes stored, would there be with an exhaust or intake leak? I have had no noticeable loss of power. I am about to leave for my appointment this morning and will update later.

Thanks for the help, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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