bandmmorris Posted March 16, 2023 Share Posted March 16, 2023 I just replaced a cracked turbo and repaired air leaks in the intercooler and one of the hoses on a 2007 Monaco Camelot with a Cummins ISL400. After all these repairs (done at the same time) I now find that my fuel economy decreased by about 30% from when I had all these problems. I spoke with Cummins and they were no help. Any suggestions on problems to look for would be appreciated. By the way, the fuel filters and air filters were replaced. Link to comment Share on other sites More sharing options...
Frank McElroy Posted March 16, 2023 Share Posted March 16, 2023 Please tell us how you determined a 30% loss in fuel economy. Was it an average of 3 full tank fills to the same level with the generator and aquahot kept off? 1 Link to comment Share on other sites More sharing options...
bandmmorris Posted March 16, 2023 Author Share Posted March 16, 2023 I have had the coach for 12 years. Historically I have averaged around 7.5 mpg. After 2 tanks since all the work the average mpg has been a little under 5.5 mpg with no generator or aquahot usage. I have also noted somewhat more black smoke than I seen before, particularly when accelerating. Link to comment Share on other sites More sharing options...
David White Posted March 16, 2023 Share Posted March 16, 2023 I recently had a similar fuel mileage decrease and it turned out to be a failed injector. You could be having a problem injector with excess fuel causing smoke. I first noticed smoke and decreased mileage, and while tracking mileage it began to fuel a power reduction. At that point, I had one bad and one with decreased performance. I went ahead and replaced all while open, since I have near 150,000 miles. Link to comment Share on other sites More sharing options...
Rikadoo Posted March 16, 2023 Share Posted March 16, 2023 Hows your power while under load? Have you checked to see if you have any codes? You mentioned you had a crack in your turbo, when you replaced it did it have a VGT actuator on it or did you just trasfere parts? Also how is it you found all the issues with you had was there a driveability issue or ? Link to comment Share on other sites More sharing options...
Simplysmn Posted March 16, 2023 Share Posted March 16, 2023 Black smoke tells me you still have a boost leak somewhere in the system. I would do a pressure test n see what you find. Atleast that is what we do on a dodge truck. I play with the first gen trucks alot. 1 Link to comment Share on other sites More sharing options...
bandmmorris Posted March 16, 2023 Author Share Posted March 16, 2023 I seem to have lots of boost (up to 37) and power seems good. I have no codes. When I replaced the turbo the replacement turbo came with a new actuator. I found the issues as a result of decreasing boost and performance and an increase in black smoke during my last trip. I don't think I have any more boost leaks as the system was checked throughly during the repairs, but I will try to check again. Link to comment Share on other sites More sharing options...
Frank McElroy Posted March 16, 2023 Share Posted March 16, 2023 Your boost pressure seems fine. A shop with the Cummins Insite software can do a cylinder diagnostic test to see if all cylinders are producing the same amount of power. But sometimes this can be misleading. However, with a warm engine, it should be able to idle on any two cylinders. A bad injector will belch soot as it tries to idle on two cylinders. It's pretty easy to identify the bad cylinder. In most all cases it's a bad injector. Hopefully you're not the exception. If all the injectors look good and all 2 cylinders idle tests generate soot, I'd then focus on an EGR issue. Sensors in the air intake manifold might not be sending the correct data to the ECM or the EGR valve could be leaking in exhaust gas which will also generate soot because the engine is now running rich. Often times, no codes are thrown when the EGR is leaking or a sensor isn't bad enough to throw a code. Are you losing any engine coolant? If you are they need to check for an EGR heat exchanger leak. 1 Link to comment Share on other sites More sharing options...
Donald Posted March 17, 2023 Share Posted March 17, 2023 Check dirty air cleaner, Different in the fuel more bio diesel? Different in the weather. Per chance you purchase some winter blend fuel mileage will drop.good luck finding the issue Link to comment Share on other sites More sharing options...
bandmmorris Posted March 17, 2023 Author Share Posted March 17, 2023 Changed the air and fuel filters about 2,000 miles ago. Since I am in the south I doubt I got any winter blend fuel. My confusion is that when I had a cracked turbo and intercooler as well as a turbo hose leak I was getting better mileage than after I fixed everything. Link to comment Share on other sites More sharing options...
Gweedo Posted March 17, 2023 Share Posted March 17, 2023 there is a "Turbo air control valve" that sits on top of the valve cover right below the engine cover. that vale has an air line that goes to the turbo, make certain that is connected. Link to comment Share on other sites More sharing options...
Solution bandmmorris Posted March 22, 2023 Author Solution Share Posted March 22, 2023 I think I may have found my problem. The gasket between the exhaust manifold and turbo was leaking. It appears that when the new turbo was installed 2 of the 4 bolts were not tightened as the nuts had fallen off. Had a new gasket put in and no leak now. Will see what the effect is on the next leg of my trip. 1 1 Link to comment Share on other sites More sharing options...
bandmmorris Posted March 23, 2023 Author Share Posted March 23, 2023 So far since the repair power is noticeably improved, excessive smoke is gone and mpg seems to have increased from around 5.5 to 8.0. Link to comment Share on other sites More sharing options...
Frank McElroy Posted March 24, 2023 Share Posted March 24, 2023 I'm curious about your boost pressure. Early on, you mentioned having plenty of turbo boost pressure - up to 37 psi. After fixing the exhaust leak and seeing higher MPG, I would think that you are now noticing higher boost pressures while driving down the road than you had before fixing the exhaust leak. Is that true? Link to comment Share on other sites More sharing options...
bandmmorris Posted March 24, 2023 Author Share Posted March 24, 2023 The boost had dropped to around 30 as the gasket deteriorated, but went back up to around 37 max after repair. I suspect the leak resulted in too much fuel for the boost I was getting throughout the power range. Link to comment Share on other sites More sharing options...
TommyL Posted April 22, 2023 Share Posted April 22, 2023 I had the same burnt through gasket. We bought the 08 camelot isl400 with 32000 mi . Had my head stuck in the closet engine access had wife start engine, puff of smoke ,that ain’t right. Two bolts loose on turbo. Wife and I replaced gasket,all good. I too had no noticeable loss of boost pressure while it was leaking 1 Link to comment Share on other sites More sharing options...
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