BAC Forum
General Boards => Technical Support => Topic started by: Kenneth Quint on March 27, 2021, 09:27:02 PM
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Long story here, please be patient. I have a 2004 Monterey with a Cummins 350 isc. I have only owned for about a year now and wanted to do all of the routine maintenance stuff so I would become more familiar with my coach. I changed the oil and filter, air filter, fuel filters, coolant and additive element. No problems. Went for test drive after and I can’t build boost pressure. When I sit in neutral I can throttle up no problem, Engine runs smooth. When in drive I can go about 20 mph on a flat surface, no power no boost pressure. Took apart connectors to turbo to inspect and it looks new, no slop in the turbine and no oil. Took into Cummins shop and they said everything is fine on the motor side, but they were only getting a 10% signal from the throttle to the ECM. I thought that it might be the throttle positioning sensor, but if it was why can I throttle up in neutral and no power in drive? Is there something that needs to be reset after servicing? I have looked high and low on the internet and cannot find anyone with the same problem. Any clues, suggestions would be appreciated.
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While you had the hoses off to the turbo, did you check the butterfly on the exhaust brake. Your symptoms sound like the exhaust brake butterfly might be stuck.
Richard
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Kenneth
Do you have a check engine light on ?
It sounds like either fuel problems or the ECM has gone into create for some reason ( engine protection ).
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Thanks for the replies Richard and Eric. I did check the butterfly valve on the exhaust brake. To add to that I drove it down a hill and switched the exhaust brake on and off, seems to be functioning fine. No check engine lights on either. As far as the ECM in create mode, I have never heard of that. Do you have any more information on that? Thanks again for your replies.
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Kenneth,
It should read “derate”. I would check fuel filters and coolant level. If it ran fine before you did the maintenance, check for loose filters and coolant level sensor. That’s where I would start. Hope this helps
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Kenneth
Sorry Frank was right that should have read derate but the darn auto correct changed it on me .
At any rate the ECM won't set a derate without an accompanying code so I also agree with Frank it sounds like A fuel issue possibly air being pulled in at one of the filters (usually the primary which is on the suction side for the fuel pump).
Air in the fuel will cause a severe lose of power to the point the engine may not even have enough power to moved the coach.
Eric
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Thanks for the replies once again. When I had the coach in the Cummins shop they suggested the filters as well. Told them I had changed them, but let them change them again. As far as the coolant sensor, would it not throw out a code? Cummins read no codes only that the ECM was only getting 10% from the throttle.
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Kenneth,
Go to the past posts and look for Charge Air Cooler or CAC. Go through the problems I had and Dave Atherton helped me. The CAC had numerous leaks and in fact burned all the insulation from the engine area and under the bedroom. To check the turbine, put a piece of paper on one side of the turbine blades and push them toward the paper. If you can pull the paper out, do the same to the other side and if the paper comes out, there is no problem with the turbo boost turbine. That valve may be sticking and that could be the problem, but because of the way they attached the CAC that caused ours to vibrate and crack. I know of one other coach that had similar problems. We had our CAC's welded and leaks are gone, but if you don't do what Dave recommends, good chances it will crack again. Be careful, though, as it could be a real fire hazard.
Roy Warren
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Kenneth
At this point you might want to look into the throttle pedal voltages using a scan tool to read what the ECM is receiving from the throttle pedal to determine wheather you have a defective throttle pedal assembly or a wiring issue.
If all the ECM is receiving is a 10 % throttle position signal from the pedal you certainly can't expect it to deliver much power.
Eric
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Kenneth,
I just spoke with Dave Atherton re your problem. He believes the cause is a bad Transition Suppressor Sensor. It is located just above the starter next to the block. It looks like an M80 firecracker with 2 wires coming from it. If it is bad, it will be relatively cool when the engine is warmed up and you are experiencing the problem. He thinks cost is around $100+.
Steve
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Wow, you guys are great! I really appreciate all the time and effort you have taken to help me out. Have been out all day, but I am going to look up the info on the Charge air cooler, I’m sure I will find some info on YouTube on how to test the pedal throttle sensor, and I will call Cummins tomorrow about the transition suppressor sensor. I will update the post as soon as I get more info. Thanks again.