Losing Boost And Smoke Sometimes

[radiographer]

I have a 2001 Monaco Diplomat Motorhome with a Cummins 330hp ISC.

Sometimes, when I remove my foot from the gas pedal, I lose my boost. When this occurs, pressing the gas peddle shows no increase in boost and black smoke pours out the exhaust. There is a small increase of RPM on the tachometer when pressing the pedal, but no power. When I pull over to the side of the road, just prior to coming to a complete stop (boost around 2.5 and 2 or 3 miles per hour), the boost suddenly returns and the coach acts as if nothing ever happened.

No warning lights come on during this process. When it occurs, I can reproduce the situation from 1-8 times by removing my foot and letting the gas pedal return to idle position. When it has occurred, I have turned off the exhaust brake and cruise control, but it does not resolve the problem. Sometimes I can drive 600 - 700 miles with no issues over a few days. Then it starts and will occur several times over 30-60 miles.

I have had 3 mechanics look at it, #1 found no codes and said the turbo looked fine (test drove it 60 miles with no failure), #2 felt it was a bad relay so I replaced the relay but the problem continues (no issues for a couple of days then occurred again), #3 found a code-I believe they said it was a Near engine shut down and stated it was a fuel filter or injector pump. He serviced the coach, replacing all filters and added some fuel additive.

Test drove up a steep 9 mile hill and had no issues or codes when he returned. Started home the next morning and lost boost 3 times in first 10 miles, each occurred when I removed my foot from the gas pedal in rush hour traffic. The remaining 350 miles home I had no issues. The loss of boost is occurring both shortly after starting and when the engine has been running for several hours.

I never have the issue occur unless I'm slowing down the coach and as long as I don't remove my foot from the pedal, it runs perfect. I don't think it is the fuel pump as it has no problem going up hills or pulling my tow vehicle. Anyone have any suggestions as to what may be causing the problem.

[wolfe10]

Radiographer,

Welcome to the FMCA Forum.

Would like to see you rule out a sticking exhaust brake. If it hangs partially closed (not snap completely open, it will give you those symptoms.

If possible, pull over when this happens and visually verify that the exhaust brake is in the full open position.

You could also visually verify it is open and then drive without using the exhaust brake for a test drive.

[dickandlois]

Radiographer!

Welcome to the Forum!

The issue Brett referred to is not uncommon and I just finished repairing my exhaust system and took some pictures of exhaust brake assemble. So I took the time to post them in the photo gallery.

http://community.fmca.com/gallery/album/466-exhaust-brake-system/

Rich.

[jlandon13399]

Rich,

Thank you for the information and pictures. I will have my exhaust brake components lubed during my next RV service.

[radiographer]

Thank you for the advice. Today, I found the PACBRAKE appeared to be dry and when I tried to move it, it felt like it is sticking sometimes. I lubed it with PACBRAKE lubricant and it is working much smoother and easier now without sticking.

While I was there, I removed the turbo actuator to test it. Looking it up online, it should work between 4psi-22psi. Putting air pressure on my old one, it would not move until I put around 20psi on it and it took almost 35+ psi to move the all the way. I'm not sure if that would cause my problem, but I will purchase a new turbo actuator Monday to replace this one.

I guess I will test drive it Monday night or Tuesday evening and will let you know if my problem has been resolved.

Thank you for you time.

[dickandlois]

Radiographer,

Look up the preload pressure for your turbo !!! If the preload is, say 25lbs. That is the point where the waste gate should start to open. To much boost and you can damage the engine. Setting the pre-load properly is critical !!!!!

Freeing up the pivot pins and linkage should help and you did mention that it was moving much easier.

The pre load on my turbo is 29.9lbs. I set it with a low pressure air regulator in the line so it was easier to read the proper pressure.

You set the point with the threaded coupler so it just slides over the waste gate actuator pin at the required pressure. Being 29.9 in my case, that keeps the gate closed until it opens at 29.9 psi.

The VGT turbos work a little different and are controlled by the ECM. This change was made to meet the newer EPA standards.

Rich

[radiographer]

Thank you to all for the help and advice. Here an update to my problem. I finally got a chance to put everything back together. I was unable to find a new turbo actuator locally, but it appeared to be working as expected and held pressure when applied, so I put the old one back on.

The Pac Brake seemed to be very difficult to work at times so I ordered lubricating oil from Pac Brake and lubricated it following the instructions. After working in the lubricant, it became much easier to open and close.

I took it for an 80 mile test drive on Sunday, starting out with the motor cold and returning it at normal operating temp. I drove it both up and down hills, using the exhaust brake the entire trip and removing my foot from the gas pedal every mile or so, I tried to reproduce the same situations that have in the past resulted in my losing all boost after slowing down. It appears the Pac Brake sticking may have been the problem as I was unable to reproduce the problem during the 80 mile trip. I also noticed the boost gauge appeared to be much more active/sensitive during the test drive.

I feel the problem has now been fixed, but really won't know for sure until I take it on the next long trip scheduled in December. Once again, thank everyone for your help.

[dickandlois]

Radiographer,

Thanks for the update!

From your description, it sound like the culprit was the Pac Brake.

The fact that your turbo linkage worked as it should when you applied air pressure to the actuator, takes it out of the equation for now!

Rich.

[sundancev]

Hello all. We own a 2004 39' Fleetwood Providence with a 350HP ISC Cummins. This thread sounds somewhat familiar to a recent problem we have been having i.e. little or no real accelaration up small hills or bridges (Skyway Bridge St. Petersburg.) We noticed the problem a few weeks back when we were traveling the East Coast of Florida on AIA and noticed lots of black smoke with taking off from stop lights and sluggish performance. We changed fuel filters immediately and found very little change. The Cummins Dealer in Orlando spent several hours checking it over and came to the conclusion it was the high pressure fuel pump not performing properly. They rebuilt half of it and took it for a test ride. I was with the techie on the test ride and thought there was much improvement and could not see much in the way of black smoke. That being said, the direction of the exhaust was more towards straight back rather than to the side and it is hard to see much smoke of any kind from the exhaust as we were at front of motor home. We also did not have the Ford Explorer being towed during the test drive.

A couple of weeks later while heading back to West Coast of Florida we noticed again the perfomrance was still somewhat sluggish and installed a new air filter despite the fact the "filter test element" in back of engine compartment showed only 2nd notch yellow level up. I looked up old records and found it was almost three years prior and some 50 thousand miles previously when air filter was last changed. It did help some but not completely. I tried the speed at wide open throttle and can only get about 67 miles per hour and get considerable smoke at that speed. When I back off throttle to 55 mph all smoke disappears. It seems as if top end at each gear is where I have most black smoke. I am a novice at diagnosing engines so anything I say about them is simply poking around in the dark. That said, I know when I was operating diesel powered boats, black smoke was typically indicative of some type of fuel problem (turbo, injector or possibly not enough air to fuel mix).

So this thread seems to suggest some possible issues for my situation (pac brake, turbo and boost?) Not sure what the boost reference is herein, but I know at top end, I do not have much boost with my engine. It was pretty good until recently and only time I had black smoke was at higher elevations where it should be expected. I know the mechanic at Cummins checked to see if turbo was open and if air intakes to CAC etc. were all tight. He said their "dyno" was down so he could not test it on that. He also said, he could spend days checking all the things that could contribute to the black smoke and weak performance.

Do any of you guys have an inkling on what my problem could be. I do not want to go back to Cummins and spend a fortune on days of diagnosis. I also do not understand what the boost used in this thread may mean. I did ask the techie to make sure the Pac Brake lever was properly lubed and he promised to do so. Should I try to make sure of running without Pac Brake engaged to somehow see if that affects it or possibly is there a somewhat easy way to make sure Pac Brake assembly is in fact completely devoid of air restriction.

Thanks in advance.

Paul

[wolfe10]

Paul,

A couple of things:

Do you have a side or rear radiator? If rear, when was the last time you cleaned the FRONT of the CAC (Charge Air Cooler)? Excessively hot intake air temperatures will certainly affect performance.

You mentioned boost a couple of times. Do you have a boost gauge? If so, what boost are you seeing?

You can visually check to see if the PacBrake has been lubed (signs of oily residue around shaft)? If not easy to do with PacBrake lube. You can also check that it is fully open (only tiny amount of piston sticking out of air cylinder). No question, an exhaust brake stuck partially shut will affect performance.

Also, check CAREFULLY for exhaust leaks: head to exhaust manifold, exhaust manifold itself and exhaust manifold to turbo. Any leak upstream of the turbo reduces potential boost. Black soot trails indicate a leak.

All of this is/should be standard checks for a diesel.

[sundancev]

Brett:

Thanks for quick reply. I am not sure I know where to find boost gauge. Only gauge I have seen is near my rear mounted radiator. It is a little clear glass/plastic upside down bowl looking thing with lines on it. As air intake pressure through system filter increases due to dust/dirt accumulation it raises the yellow line thereby indicating air filter needing change.

I looked and tech also looked carefully for signs of exhaust leaks. I will check PAC brake piston carefully again. I will send photo of what it looks like if you don't mind me sending to you. It has been a while since I cleaned CAC. As has been discussed herein it is really difficulty to do on a rear mounted radiator.

Last time Lazy Days in Tampa did it with some type chemical from back side rather than front side. The tech claimed it would flow through to CAC side which I doubted. That being said, it did work. I have had very little change in engine operating temperature for years. Gauge indicator is very near quarter mark and only on very hot days with me running flat out will it go up to perhaps half way between quarter and half marks.

When the tech cleaned the radiator with the chemical, I also decided to run a line from the blow by tube to the rear of my motor home so the oily mist and dirt from tires would substantially reduce the build up going to CAC. Lots of mechanics over the years have laughed at it in wonderment until I explain it to them.

They quickly change their mind and tell me, it was good thinking. In actual fact, I got that good thinking from reading your forum responses herein years ago.

[elkhartjim]

The following link will provide you some information on the Freightliner MMDC unit. You should be able to get a turbo boost read out from this display.

http://www.rvtechlibrary.com/electronics/mmdc_overview.php

[sundancev]

]

Hello All. Attached are 4 photo's I took minutes ago from above my PAC Brake Actuator (I think that might be what it is called.) First shows as linkage as I found when I opened engine hatch. I then took the Pac Brake actuator loose so I could rotate the exhaust valve coming from turbo into exhaust pipe. There appears to be a spring involved but it does not seem to have any tension on it as the lever only moves if I move it with my fingers. I wonder if this should in fact need to be spring loaded to a fully open position when PAC brake is not engaged. Since engine is off, nothing is engaged. If my surmise is correct this might indicate the problem I have been having if exhaust port is partially closed all the time. Thanks. Paul

[wolfe10]

Yes, the spring should STRONGLY hold the exhaust brake in the open position. In fact, unless you have gorilla strength, you will not be able to close it by hand.

[sundancev]

The rest of the Story. After mucho money spent with Cummins (amount of which I am embarrassed to tell you) I think I have the problem solved. Based on Brett's comments and Rich's initial photo's of his PAC Brake assembly I started looking at mine closer and realized the air cylinder shaft did not appear to be fully retracted-- perhaps 75% but not 100%.

Since my boat diesels did not need Exhaust Brakes this was somewhat new to me, but I did realize fuel and air mixtures usually meant full air was needed when full fuel throttle was extended. I called PAC Brake and spoke to a very nice gentlemen who told me if I released any air pressure present in the cylinder, the shaft should fully retract. It did not. So before driving to Camping World to buy new cylinder I whacked the shaft and bingo it retracted. I then WD-40'ed the shaft and worked it a few times by hand.

Brett was right, you need to be a gorilla to pull the shaft out by hand. Apparently due to no use for several months while camping in South Miami this winter, the shaft got a little sticky. For now it is going in and out like it should so will try to get by with it as is. PAC Brake people thought it would be fine with some lube.

Once again FMCA stalwarts have come to my rescue and saved me untold amounts of money.

I was all set to go to Cummins and try to get on their dyno before heading north and west for the summer.

Many thanks to you all again.

Paul

[obedb]

Turbo Actuator might be what I was taught to call a waste gate. It opens to bleed turbo pressure out at a set point speced by the engine manufacturer. If it opens before spec you will lose boost. Some people (truckers) not knowing the possible problems monkey with them.

[DaveAtherton]

Radiografter, reply to ISC cummins 330 engine. What you have going on fuel injection pump problem

on your CAP'S fuel system. Engine ECM has detected an overpumping malfunction in the cummins

accumulator pump system ( CAP'S ) pump. Effect: Lowpower, possible engine shut down Fault Code

329. Here is the fix, the above will generate fault code 539 Transient suppressor circuit which detected

open circuit to the injection valve in engine harness. Part number for transient surge suppressor cummins part

3944110 cost $ 105.70 All this part is a big resistor for the CAP'S system. location follow wire about 12

inches off back of Cap's pump will see resister in metal clip with plastic zip tie

Dave Atherton Retired Cat Mechanic