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kwl0525

Cummins ISB 300 - engine light and idle speed

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I actually have a couple questions/concerns and thought I throw this out to see if anyone has advices or experience with this.  I have  2003 Monaco Cayman with the Cummins ISB300 and an Allison 5 speed transmission.

1) The other day when the exhaust brake engaged (PacBrake) and the transmission downshifts ( and RPMs increase), the Engine Light comes on and then goes out after the RPMs decrease.  I don't have any loss of power or anything, but I've never had this occur before. 

Coincidently....

2) Starting last year, I started noticing that when I start the unit (or when it's idling after being driven) it seems to 'hunt' for an idle speed to settle at and my tachometer is constantly bouncing all over the place, even when driving down the road.  They are massive speed variations, but you can hear it.  I know the air compressor comes on immediately for the suspension, etc., but I don't think that is the cause of the 'hunting'. 

Could issue 1 be caused by the engine RPMs exceeding 2500 (the stated governed speed)? 

Could the idle speed sensor be screwed up/bad or the something with engine electronics ( I miss my old, mechanical 5.9 some days)?

Any input is appreciated!

 

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kwl0525, I will off my thoughts on the items. I will highlight them

I actually have a couple questions/concerns and thought I throw this out to see if anyone has advices or experience with this.  I have  2003 Monaco Cayman with the Cummins ISB300 and an Allison 5 speed transmission.

1) The other day when the exhaust brake engaged (PacBrake) and the transmission downshifts ( and RPMs increase), the Engine Light comes on and then goes out after the RPMs decrease.  I don't have any loss of power or anything, but I've never had this occur before. 

 Think that you are getting an over speed indication. Try to maintain an RPM level around 2300 max. Is this the only time you get a yellow warning light ?

2) Starting last year, I started noticing that when I start the unit (or when it's idling after being driven) it seems to 'hunt' for an idle speed to settle at and my tachometer is constantly bouncing all over the place, even when driving down the road.  They are massive speed variations, but you can hear it.  I know the air compressor comes on immediately for the suspension, etc., but I don't think that is the cause of the 'hunting'. 

I have experienced a similar issue, that has been caused by items.

       A. High heat in the engine compartment,  serpentine belt needed replacement,  Belt tension-er  being defective, Defective cooling system thermostat, Failed engine alternator. The other items that might come into play are the engine speed sensor is failing, a weak, corroded connection at the sensor or at the ECM primary 50 pin connection.

        B. Low coolant level  could come into play. 

                                  Question - when was the radiator and the CAC / Inter cooler cleaned ?

         Last time the fuel filters where changed?  Your coach year / if it is a 2002 to 04 - you will have an ISB-02 series engine and they are the model years that have a 3rd. fuel filter connected inline most often in the frame rail behind the rear axle on the drivers side, BUT it has popped up in other locations at times and it gets missed 99.9% of the time. just gets over looked or the shops have no clue it is there.

( I miss my old, mechanical 5.9 some days)? Simple is better, with less to go wrong, but there are some other issues that the newer setups have cured.

         I don't have any loss of power or anything, but I've never had this occur before.

Question - how old is your fuel lift pump?

Rich.

 

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Rich - The 2 fuel filters were changed 2 years ago.  I need to look again to see if there is a 3rd one lurking somewhere.  Coolant level is good and it was changed at the same time as the fuel filters.  I don't know when the radiator and CAC were cleaned, but they appear to be in good shape and aren't gunked up with oily grime buildup. 

Yes, the engine light only comes on when the exhaust brake kicks in and the unit downshifts, which immediately increases the RPMs.  Once the RPMs reduce, the engine light goes out.

I still need to check out your other suggestions. 

Thanks!

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This is not pertinent to your primary issue, but a couple of points:

To check the CAC/radiator for cleanliness, you HAVE TO LOOK FROM THE FRONT (from the bedroom/closed). The dirt will be on the front of the CAC.  Look at the perimeter-- particularly lower perimeter-- the fan blades sling the dirt to the perimeter.

There is no "average life" for fuel filters-- if all they see is clean fuel, they can go a long long time.  But, one tank of contaminated fuel can clog them in a few miles.

Does the engine speed when you use the engine brake exceed Cummins's "overspeed" max for your engine.  Call Cummins with your engine serial number.  Good numbers to ask are:

Maximum torque RPM (you do not want to operate at heavy loads below this number.

Max HP RPM (no reason to exceed this with the engine working)

Governed RPM (max speed with the engine working)

Overspeed RPM (max speed with no load (i.e. with engine brake on)

 

Cummins 800 343-7357

 

 

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2 hours ago, kwl0525 said:

Rich - The 2 fuel filters were changed 2 years ago.  I need to look again to see if there is a 3rd one lurking somewhere.  Coolant level is good and it was changed at the same time as the fuel filters.  I don't know when the radiator and CAC were cleaned, but they appear to be in good shape and aren't gunked up with oily grime buildup. 

Yes, the engine light only comes on when the exhaust brake kicks in and the unit downshifts, which immediately increases the RPMs.  Once the RPMs reduce, the engine light goes out.

I still need to check out your other suggestions. 

Thanks!

Brett, posted some good information just prior to me-so look it over.

When I asked how old the fuel lift pump was,  maybe it would have been better to ask how many miles are on the coach and are you a second owner? 

That third filter is like 30 micros and they pick up the bigger stuff. The common problem is loos of power, but it could  easily cause the engine to surge because of a reduced fuel flow and Cummings fuel pumps can be very temperamental.  

Brett, mentioned calling them regarding RPM items and a Call to Freightliner will get you an engine serial number. With that and they also would have installed that 3rd. filter, because it is not mounted on the engine.

Rich.

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2 hours ago, wolfe10 said:

Overspeed RPM (max speed with no load (i.e. with engine brake on)

This raised an eye brow for something that has bothered me since we have owned our coach. I called Cummins, on deceleration I have hit 2500 RPM's (on the tach), which is too high, max should be 2300 RPM's. I have to verify my tach is accurate also. Good to figure that out now rather than a Scatted ISL all over the highway :wacko:. I usually step on the brake pedal to get it under control, but it always bothered me. 

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Rich/Brett - The coach has 34,500 miles on it and I'm the 2nd owner.  My chassis isn't a Freightliner, its a Monaco Roadmaster R4R chassis.  I have the Cummins engine # and will be contacting them to confirm max limit.  I believe the deceleration/down shifting is causing the RPMs to exceed what they have designated as a max RPM.  If I'm correct, that begs the question 'why has it started doing this now?'   This is first year I've noticed this occurring.

I still need to investigate your options regarding my 'dancing tach'....

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Thanks.

Look forward to your posting what Cummins tells you as well as max RPM you are seeing.

And, whether Cummins thinks this will set a code. AND that is the code you have.

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kwl0525, 

The coach has 34,500 miles on it and I'm the 2nd owner.  The mileage on the coach, puts the fuel lift pump in the range for the OEM fuel pump to fail !!!!

If you do not have fuel pressure gauge set up Have it checked !!!!!  Bad lift pumps and cause serious damage to the injector pumps.  Fuel flow and pressure is critical. The fuel is used to keep the injector pump cool.

Rich.

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Less than 2,200 miles a year, is not a good thing for a Diesel.  A lot of bad things happen, when they just sit.

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After you check your fuel preshure I would run a couple tanks with a rich mix of Diesel Kleen. See if that helps the idle and general performance.

Bill

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