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Jamey g · 02-15-2012, 10:35 AM

Hi my dads coach is a 97 monaco with a cummins it takes about 5-10 min of driving before it gets boost i have replaced all the fuel and air filters and it is still the same after 5 min of driving it get boost before that the gauge is at 0 and it is a real loss of power took it to cummins they fixed a few clamps but still does it any sugestions Thanks Jamey

Papa_Jim · 02-15-2012, 09:30 PM

When you do get boost, how much? What's the gauge read?

HeapBigEngin · 02-15-2012, 10:21 PM

You need to give us a bit more info. What Cummins engine is it? How many miles on the coach? Does it have an aftermarket "kit" on it like the Banks System? Is the engine equiped with an emission system that includes things like a MAP (manifold absolute pressure) sensor?

Without more info, I would suggest you go after the basic things first. Perhaps something needs to be warmed up a bit before boost arives. And, if so, maybe you have a small leak somewhere in the air intake system, vacuum system or boost system that needs "time" to warm up/expand and obtain a better seal. I would very carefully check all hoses, vacuum lines and, especially, all connections relating to the intake system (including the turbo area), the vacuum system and the EGR system. A split hose, a pinhole or a loose/bad clamp may be hard to see, but they can cause many driveability problems. Time and attention to detail can be very useful in tracking down these gremlins.

I have lost count of the number of posts I have read on this forum regarding performance and driveability issues that were resolved by replacing a simple vacuum line, a hose or a faulty clamp somewhere. You might do a forum search on the subject...this place is a goldmine of info. PLEASE let us know what you find out....thanks!

Mr_D · 02-15-2012, 10:46 PM

Having a Banks kit should not affect the turbo pressure except to raise it. We have an ISC with Banks and have never had any trouble with turbo pressure other than I'm finding the air filter is too small now and I'm getting high readings on the filter minder.

HeapBigEngin · 02-15-2012, 11:54 PM

Quote:

Originally Posted by Mr_D

Having a Banks kit should not affect the turbo pressure except to raise it. We have an ISC with Banks and have never had any trouble with turbo pressure other than I'm finding the air filter is too small now and I'm getting high readings on the filter minder.

As you know, if the Banks Ottomind computer goes haywire, the engine goes back to "stock" configuration, including boost readings. And, of course, performance suffers. Unfortunately, a "shorted" internal Ottomind gauge circuit can also cause the boost gauge to become non-functional and read '0' boost since the Ottomind and the gauge are no longer "communicating". I know that that can happen 'cause that is exactly what happened to mine last year....along with a number of other odd things that occured, including diminished performance. A new Ottomind resolved all of our issues. Not sure if the fellow has a Banks system, but methinks it is worth asking.

Jamey g · 02-16-2012, 09:07 AM

the cummins engine is a 325 No Banks kit all stock iam going to check all the lines today for the 3rd time going to use a spray botle with soapy water and a flashlight i can let this coach run for fifteen min in my shop ant take off and it still takes at least 5 min before i have any boost and the the most boost i see is 20 Thank you for any ideas Jamey

HeapBigEngin · 02-16-2012, 10:06 AM

Jamey g....thanks for the info. Not familiar with the 325. Again, I would suggest you do a forum search if you have not already done so. This can save a lot of time and aggravation if someone else has already tracked something like this down before...just MO. Please let us know how it goes....thanks!

Mike Canter · 02-16-2012, 10:13 AM

Jamey, got a question for you.......when you get no boost does the power from the engine go away big time or does it still feel peppy. I have lost boost on my previous MH several times for one reason or another and let me tell you the power just flat goes away when it happened. If it is still running OK and still has the same pep as when it shows boost then it might just be the boost gauge is bad. On my current MH my boost gauge is mechanical via a small tube off the intake manifold and there was a small "spike supressor" screwed into the intake manifold that the tube connected to. This spike supressor is to slow down the needle swing on the gauge and it was blocked by carbon and acted weird. I finally took it off and drilled it out with a real small drill and I mean real small and it has worked OK since then.

Jamey g · 02-16-2012, 10:40 AM

Hi Mike when i first take of for about five min no boost on the gauge and a real loss of power and then when it gets boost it runs with a perfect amout of power.I just checked all the lines with soapy water and a flash light and cant come up with any breaks or pin holes i have a week of serching Iam half tempted to pull the turbo off and inspect that

Mike Canter · 02-16-2012, 10:53 AM

I have taken turbo's apart and I don't think you will gain anything by taking it off. The only possibility you might see is it not spinning freely when cold and spinning OK when hot. If so it would be the bearings getting ready to go. You might check the four bolts/nuts that hold the turbo onto the manifold and make sure they are tight.

Here is something to think about. It takes exhaust gases to spin up the turbo. If the motor is running real lean then it will not spin up the turbo and you will not have power. In that first five minutes can you get the motor to RPM?

Jamey g · 02-16-2012, 11:14 AM

ya it will rev right up when it is cold

Coma · 02-16-2012, 11:53 AM

ISB325?I'd guess a stuck waste gate.

Mike Canter · 02-16-2012, 12:29 PM

Waste gates do not normally open and close on a diesel turbo as a routine control because they are set a pretty high boost levels and not used in normal driving. You can normally disconnect them and not notice the difference. The way you can eliminate that is to disconnect the pressure line to the waste gate and plug it and see if it makes any difference.

Still thinking

HeapBigEngin · 02-16-2012, 01:17 PM

Mike....very interesting and helpful comments. Obviously, something's keeping that turbo from spooling up until a certain temperature is reached or a certain amount of time has passed. Are there any electronics, sensors or egr components on that engine that could be involved? (I have no expereince on his engine.) Wondering if he has a minor exhaust leak somewhere ahead of the turbo. Would that be enough to cause the turbo to stumble a bit until the exhaust gasket expands from heat and reseals itself to some degree? A cracked exhaust manifold or leaking manifold gasket? Your comments re turbo bearings is interesting and scary at the same time. Jamey, hang in there. Most of us have been where you are, some of us more than once! Frustrating...but you'll find it. Thanks for posting what's going on....