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Old 04-21-2019, 04:50 PM   #1
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Low boost below 170 degrees ISM500

I occasionally have low boost (between 2 and 10) when the Cummins ISM500 is below 170 degrees. Once the temp has reached 170 degrees and the engine is shut down, wait 60 seconds, and restarted, boost is normal (around 4 to 32). Boost will remain normal once restarted. I have found other threads with this problem but not sure of a solution. I am assuming this is a sensor problem. There are no CHK ENG lights or codes. Does anyone have a fix?
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Old 04-21-2019, 08:14 PM   #2
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Hmmm, in another forum, with coaches with the ISL400 Engine, a long discussion was held about when to load up the engine (highway speeds). Cummins was consulted and their recommendation was never move it until 140, then idle or little load until at least 160, better 170 degrees F. Now my guess based on age of unit, your CAC has a leak, and as it expands it closes some. I would have Cummins do a leak test on it, just to be safe. It could also be a turbo/CAC hose connection which when cold allows loss, but expands when warm and seals itself. If you are handy, open up compartment and see if any of the clamps are lose on those hose to metal pipe connections. You have an air leak someplace. Good Luck.
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Old 04-21-2019, 08:25 PM   #3
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We owned a 04 Essex with the 500 ISM for 14 years and had over 140K miles we put on it. We had both the ECM reading boost plus we added a EGT and separate boost gauge and I can't ever remember having this issue. I might be that we never pushed the engine until we were warmed. We did learn that we had over 32 PSI boost with the 2nd boost gauge. The ESM on registered boost to 32 but with other gauge we had reading as high as 45psi. If I was to think what it would be caused by it would be the ECM limiting boost till engine is warmed up to 170 degrees.
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Old 04-21-2019, 08:44 PM   #4
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Tom may be right, ECM may be limiting fuel until engine is warmed up. Never really looked at mine when cold, but going to full boost conditions when engine is not warmed up is probably not the best idea.
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Old 04-22-2019, 04:51 AM   #5
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Quote:
Originally Posted by tom chelbana View Post
We owned a 04 Essex with the 500 ISM for 14 years and had over 140K miles we put on it. We had both the ECM reading boost plus we added a EGT and separate boost gauge and I can't ever remember having this issue. I might be that we never pushed the engine until we were warmed. We did learn that we had over 32 PSI boost with the 2nd boost gauge. The ESM on registered boost to 32 but with other gauge we had reading as high as 45psi. If I was to think what it would be caused by it would be the ECM limiting boost till engine is warmed up to 170 degrees.
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That's not quite the scenario. I'm not talking about pushing the engine when cold. This is what happens:

1. start cold engine.
2. boost is limited (sometimes) and will remain limited until 2 conditions are met.
3. those conditions are: temp has reached 170 and engine has been shut down and restarted.

In other words, when cold and first started, I only have a range of boost at around 1 to 10 (apparently running de-rated). When warm and restarted, the boost is in a range of about 4 -32.
I have NOT done extensive testing to see if the full boost is available at 140/150/160 etc.

Boost and temp are reported by my TripTec unit and a ScanGaugeD.
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Old 04-22-2019, 04:53 AM   #6
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Originally Posted by Old-RVer View Post
Hmmm, in another forum, with coaches with the ISL400 Engine, a long discussion was held about when to load up the engine (highway speeds). Cummins was consulted and their recommendation was never move it until 140, then idle or little load until at least 160, better 170 degrees F. Now my guess based on age of unit, your CAC has a leak, and as it expands it closes some. I would have Cummins do a leak test on it, just to be safe. It could also be a turbo/CAC hose connection which when cold allows loss, but expands when warm and seals itself. If you are handy, open up compartment and see if any of the clamps are lose on those hose to metal pipe connections. You have an air leak someplace. Good Luck.

Thanks, I'll have a look.
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Old 04-22-2019, 05:08 AM   #7
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This thread is very similar but I don't see a reported fix.
http://www.irv2.com/forums/f123/500h...ms-150520.html
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Old 05-26-2019, 08:16 PM   #8
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#MeToo!

I think, kinda sorta.

I believe I am experiencing something similar. For me, this started at the end of my fall 2018 trip last October.

I got some fuel in Grand Junction... About 3/8 a tank to get to SLC. About 100 miles later, I was climbing a hill and experienced a very brief check engine alarm. 2 seconds and then gone. Happened again a while later. That was it. When I checked, there was now fault and no codes.

I had no idea of what was wrong, so I figured maybe I have some water in my tank. I got my coach ready for storage with an oil change and filter change and filled up my tank and added the necessary fuel additives and left my coach alone for the winter. I experienced the mysterious check engine light 1 more time over 5 hours of driving.

5 months later, I begin the process of using my coach once again. I had some issues, so I drove my coach to a service facility and experienced the check engine light one more time. (4th instance). I am driving rather flat terrain, but I sensed a lack of engine performance. I couldn't put my finger on the issue as I had not driven my coach for several months.

I read this thread in early April and made a note to monitor my turbo boost. Today was that day. I used the spartan display to show the turbo boost while I did some driving. I made it a point to warm up the engine and then begin to aggressively accelerate, especially from stops and while climbing. I drove 20 miles and noticed the max turbo boost as in the 28-32 range. I also experienced the intermittent check engine warning about a dozen times. Almost always while accelerating while climbing.

I stopped at a truck stop to top off my fuel tank. Naturally the engine is at temp and I turned off the engine while adding fuel.

I then drive back to my storage facility and notice the max boost is now ranging from 32 to 39. There are no check engine warnings at all.

So, it appears I am now experiencing a lower turbo boost after starting a cold engine. This situation seems to improve after restarting the engine after the engine is at operating temp.

One other observation. I recently changed my air filter and reset the monitor. After driving I noticed the monitor barely registering any restriction. I worry about this as I want to make sure the air filter is properly installed and there are no intake leaks.

Today, I reset the filter before I drove to the truck stop. At the truck stop, I checked the monitor and the monitor had barely moved from the reset position. I reset the monitor again and drove back to my storage facility. I checked the monitor (with the higher boost) and the monitor was reporting a higher vacuum (this is reassuring to me).

So, it appears my coach is suffering this lower boost situation, but with the mysterious check engine light.

Is there any kind of update on this situation?
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Old 05-27-2019, 03:38 AM   #9
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Quote:
Originally Posted by azSkier View Post
#MeToo!

I think, kinda sorta.

I believe I am experiencing something similar. For me, this started at the end of my fall 2018 trip last October.

I got some fuel in Grand Junction... About 3/8 a tank to get to SLC. About 100 miles later, I was climbing a hill and experienced a very brief check engine alarm. 2 seconds and then gone. Happened again a while later. That was it. When I checked, there was now fault and no codes.

I had no idea of what was wrong, so I figured maybe I have some water in my tank. I got my coach ready for storage with an oil change and filter change and filled up my tank and added the necessary fuel additives and left my coach alone for the winter. I experienced the mysterious check engine light 1 more time over 5 hours of driving.

5 months later, I begin the process of using my coach once again. I had some issues, so I drove my coach to a service facility and experienced the check engine light one more time. (4th instance). I am driving rather flat terrain, but I sensed a lack of engine performance. I couldn't put my finger on the issue as I had not driven my coach for several months.

I read this thread in early April and made a note to monitor my turbo boost. Today was that day. I used the spartan display to show the turbo boost while I did some driving. I made it a point to warm up the engine and then begin to aggressively accelerate, especially from stops and while climbing. I drove 20 miles and noticed the max turbo boost as in the 28-32 range. I also experienced the intermittent check engine warning about a dozen times. Almost always while accelerating while climbing.

I stopped at a truck stop to top off my fuel tank. Naturally the engine is at temp and I turned off the engine while adding fuel.

I then drive back to my storage facility and notice the max boost is now ranging from 32 to 39. There are no check engine warnings at all.

So, it appears I am now experiencing a lower turbo boost after starting a cold engine. This situation seems to improve after restarting the engine after the engine is at operating temp.

One other observation. I recently changed my air filter and reset the monitor. After driving I noticed the monitor barely registering any restriction. I worry about this as I want to make sure the air filter is properly installed and there are no intake leaks.

Today, I reset the filter before I drove to the truck stop. At the truck stop, I checked the monitor and the monitor had barely moved from the reset position. I reset the monitor again and drove back to my storage facility. I checked the monitor (with the higher boost) and the monitor was reporting a higher vacuum (this is reassuring to me).

So, it appears my coach is suffering this lower boost situation, but with the mysterious check engine light.

Is there any kind of update on this situation?

No updates yet. I can clear mine with a stop engine/restart after it has reached operating temp and it will stay at normal boost for the rest of the day. I have a new ambient pressure sensor ready to go in but haven't had the opportunity yet (traveling in Maine). At least 1 other person reported that fixed a "similar" problem on an ISM 500. I also have an occasional chk eng that clears within a few seconds and no codes. I have TripTek and a ScanD so see the boost on the displays. Normal full throttle is 32 and reduced (derated mode) is about 9. I'd put the sensor in if I was in a better site ... it's tough to reach and hidden behind the fuel pump. See "Ugly Fix" for pics of location.



Bruce
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Old 05-27-2019, 07:44 AM   #10
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So, ScanD will not capture these intermittent Check Engine codes? That is disappointing.
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Old 05-27-2019, 10:48 AM   #11
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So, ScanD will not capture these intermittent Check Engine codes? That is disappointing.

Correct ... I do not have a latched ChkEng light nor does ScanD see/log an error. Mostly, I get a brief light and a brief alarm (beep).
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