CHEESE_WAGON
Traveling
As some may know, I offered and agreed to transport Manidinee's recent purchase of a 40-ft Blue Bird RE (98 or 99 model), equipped with Cummins CAPS-equipped 8.3 and Allison MD3060.
The bus has developed some running problems a little over halfway into the trip after running well for well over 1000 miles, and after making arrangements to get the bus looked at, Mandinee has persuaded me to post here seeking opinions on the matter.
After leaving a hotel near the I-79/I-80 junction (just before getting into the tougher hills of PA on I-80), I started noticing a sound sort of like machine gun fire when the engine dropped to 1500 rpm. I assumed the engine was lugging and needed a lower gear, so I manually downshifted the trans and all was well.
I assumed the engine was lugging, but was curious why the transmission was not automatically downshifting as an automatic should do under that condition. Other than that, the bus seemed to be lacking a little power on hills, but not overly so, and otherwise appeared to be running fine. No warning lights, oil pressure, temp, all were looking good.
When I made a pit stop a while later in Drums, PA, the engine had a noticeable lope when it came to a stop and was noticeably louder as well. Turns out the flex hose between what I assume to be the turbo down pipe and the muffler had broken.
The only shop in the immediate area that would look at it charged the owner four hours labor for what wound up being two hours work, and fixed only the exhaust, not addressing the lope, which was obvious. Idiots. Sherwood Freightliner Drums, PA - to be avoided. It's clear to me they didn't really want to deal with this thing.
I found another shop about nine miles away and proceeded there. Interesting note here. The bus was billowing white smoke getting onto the highway, but cleared up when I downshifted the trans to fourth gear, which got the rpm up around 2100. At that point, the bus seemed happy and I could not tell whether it was continuing to smoke or not. I know that black smoke indicates too much fuel, and white smoke indicates insufficient or no fuel, so why would white smoke clear up at higher rpm?
The shop tinkered with some of the injectors and found one leaking (oil, I think, as it has been throwing a small amount of black residue out the rear of the bus), another one loose, which they said had backed off two turns. These two injectors, in question, are the two directly adjacent to the bellhousing end of the engine. I'm thinking the residue that I had thought could be from the pinion seal could very well have been from this injector leaking, which means this bus spent a lot of time idling and possibly more time reversing than forward.
What's curious here is that I watched and listened as they tested each injector by cracking it open and re-tightening to see how it affected the engine. The engine developed the same misfire each time. The white smoke, however, did not go away when the misfire was corrected.
It is now my opinion that the sound I heard like machine-gun fire could very well have been a cylinder misfire, but unfortunately it was dark and I could not see if the engine was smoking. It was a reasonable assumption that the engine was simply lugging at that point, as there seemed to be no other obvious conclusion. Above 1500 rpm, the bus seemed to run fine. If I had noticed any problems after downshifting the trans, I would have stopped to verify what was going on.
With CAPS putting a computer in the loop of fuel control, however, I couldn't be sure how much further the bus was going to make it under its own power and whether it could make it to another shop under its own power. Not wanting to make Mandinee and her husband pay for a tow bill if it wasn't necessary, I recommended she make arrangements for an on-site Cummins tech to give a more specific diagnosis and determine whether a shop visit is needed. Hopefully if it is just injectors, that can be done on-site without a tow bill. Or, if a shop is required and it is just injectors, that can be done by the shop it is currently parked at.
I'm just curious because the symptoms are very confusing. Clearing up and running better as RPM rises would suggest overfueling, which would be black smoke. There was black smoke initially when the exhaust was broken open. Since then it has been white smoke, however, and it seems to me white smoke should get worse as RPM climbs.
Also, it almost appears to be sporadic in that it does not go away at idle regardless of misfire, gets extreme on low-speed acceleration, but clears up above 1500 rpm at speed. Granted, I am not a diesel mechanic by trade, but it does not make sense to me at all. Seems me overfueling would clear up with RPM rise, which would be black smoke. Seems to me a no-fuel misfire would get worse and worse as RPM rose.
In a nutshell, it blows white smoke from idle to about 1500 rpm, possibly more, especially on acceleration, has a chattering noise in mid-range RPM, and clears up at 1800-2100 rpm cruising, running fine with little to no smoke. After researching a bit about the operation of the CAPS system, I'm leaning toward the air bleeder or pressure control valves in the CAPS pump, but there are obvious issues with at least two injectors, as I am not convinced this is the first time that the loose injector has backed off.
Has anyone else seen this before with a CAPS system, and if so, what was the problem? Also, is the CAPS system technically an HEUI system? It certainly seems like it, though I thought these didn't show up until the mid-2000s.
Side note: Once this issue is resolved, along with a couple other things I feel need work, I think Mandinee has made a decent purchase. This bus drives fairly well, but seems to have a bit of play in the steering. I am curious if REs tend to wander more on bumps due to not having the weight of the engine in the front, and whether this could exacerbate play in the steering gear box or linkage?
The bus has developed some running problems a little over halfway into the trip after running well for well over 1000 miles, and after making arrangements to get the bus looked at, Mandinee has persuaded me to post here seeking opinions on the matter.
After leaving a hotel near the I-79/I-80 junction (just before getting into the tougher hills of PA on I-80), I started noticing a sound sort of like machine gun fire when the engine dropped to 1500 rpm. I assumed the engine was lugging and needed a lower gear, so I manually downshifted the trans and all was well.
I assumed the engine was lugging, but was curious why the transmission was not automatically downshifting as an automatic should do under that condition. Other than that, the bus seemed to be lacking a little power on hills, but not overly so, and otherwise appeared to be running fine. No warning lights, oil pressure, temp, all were looking good.
When I made a pit stop a while later in Drums, PA, the engine had a noticeable lope when it came to a stop and was noticeably louder as well. Turns out the flex hose between what I assume to be the turbo down pipe and the muffler had broken.
The only shop in the immediate area that would look at it charged the owner four hours labor for what wound up being two hours work, and fixed only the exhaust, not addressing the lope, which was obvious. Idiots. Sherwood Freightliner Drums, PA - to be avoided. It's clear to me they didn't really want to deal with this thing.
I found another shop about nine miles away and proceeded there. Interesting note here. The bus was billowing white smoke getting onto the highway, but cleared up when I downshifted the trans to fourth gear, which got the rpm up around 2100. At that point, the bus seemed happy and I could not tell whether it was continuing to smoke or not. I know that black smoke indicates too much fuel, and white smoke indicates insufficient or no fuel, so why would white smoke clear up at higher rpm?
The shop tinkered with some of the injectors and found one leaking (oil, I think, as it has been throwing a small amount of black residue out the rear of the bus), another one loose, which they said had backed off two turns. These two injectors, in question, are the two directly adjacent to the bellhousing end of the engine. I'm thinking the residue that I had thought could be from the pinion seal could very well have been from this injector leaking, which means this bus spent a lot of time idling and possibly more time reversing than forward.
What's curious here is that I watched and listened as they tested each injector by cracking it open and re-tightening to see how it affected the engine. The engine developed the same misfire each time. The white smoke, however, did not go away when the misfire was corrected.
It is now my opinion that the sound I heard like machine-gun fire could very well have been a cylinder misfire, but unfortunately it was dark and I could not see if the engine was smoking. It was a reasonable assumption that the engine was simply lugging at that point, as there seemed to be no other obvious conclusion. Above 1500 rpm, the bus seemed to run fine. If I had noticed any problems after downshifting the trans, I would have stopped to verify what was going on.
With CAPS putting a computer in the loop of fuel control, however, I couldn't be sure how much further the bus was going to make it under its own power and whether it could make it to another shop under its own power. Not wanting to make Mandinee and her husband pay for a tow bill if it wasn't necessary, I recommended she make arrangements for an on-site Cummins tech to give a more specific diagnosis and determine whether a shop visit is needed. Hopefully if it is just injectors, that can be done on-site without a tow bill. Or, if a shop is required and it is just injectors, that can be done by the shop it is currently parked at.
I'm just curious because the symptoms are very confusing. Clearing up and running better as RPM rises would suggest overfueling, which would be black smoke. There was black smoke initially when the exhaust was broken open. Since then it has been white smoke, however, and it seems to me white smoke should get worse as RPM climbs.
Also, it almost appears to be sporadic in that it does not go away at idle regardless of misfire, gets extreme on low-speed acceleration, but clears up above 1500 rpm at speed. Granted, I am not a diesel mechanic by trade, but it does not make sense to me at all. Seems me overfueling would clear up with RPM rise, which would be black smoke. Seems to me a no-fuel misfire would get worse and worse as RPM rose.
In a nutshell, it blows white smoke from idle to about 1500 rpm, possibly more, especially on acceleration, has a chattering noise in mid-range RPM, and clears up at 1800-2100 rpm cruising, running fine with little to no smoke. After researching a bit about the operation of the CAPS system, I'm leaning toward the air bleeder or pressure control valves in the CAPS pump, but there are obvious issues with at least two injectors, as I am not convinced this is the first time that the loose injector has backed off.
Has anyone else seen this before with a CAPS system, and if so, what was the problem? Also, is the CAPS system technically an HEUI system? It certainly seems like it, though I thought these didn't show up until the mid-2000s.
Side note: Once this issue is resolved, along with a couple other things I feel need work, I think Mandinee has made a decent purchase. This bus drives fairly well, but seems to have a bit of play in the steering. I am curious if REs tend to wander more on bumps due to not having the weight of the engine in the front, and whether this could exacerbate play in the steering gear box or linkage?
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425-450 miles I believe. Barring any other issues, if this is an injector issue, once resolved it will continue to run properly and finish the trip. Couple other things will need attention for long-term roadworthiness, but nothing that I believe will prevent delivery.
