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.

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.

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.