Cummins ISL 400hp -Losing Power On Uphill

[rwitt]

We traveled south on US 65 to Branson, MO today towing a 2012 Jeep GC. As we got into the Ozarks we started really slowing down going up hills. It was doing fine on less steep hills, but slowed to 30-35 mph on the ones around Branson.

These are not like we are crossing the Rockies. Just wondering if anyone has any ideas.

[hermanmullins]

rwitt,

When was the last time you changed to fuel filter? A filter will cause a loss in power. Also how is your boost? A stuck waste gate on the Turbo can give the same troubles.

Herman

[dickandlois]

Herman mentioned the waste gate and you might want to check engine brake is not sticking. Will increase back pressure and that will reduce power.

Rich.

[rwitt]

Herman,

Thanks for answering. All filters were changed in May. I don't remember looking at the boost gage while I was having the problem. It did fine on up hills until we got to the steeper ones. There was some some power loss on all hills but not like this. There is plenty of power until it starts a climb. I do know that when I was noticing the boost it was peaking at 25-30.

Just can't figure why I have plenty of power until I start up steeper hills.

Ron

[rwitt]

Thanks Rich,

How would I check for the engine break sticking. I did use it a couple of time on the steeper downhills, but I can't remember if I had used it before I had the problem on the first hill.

Ron

[dickandlois]

Ron, You need to get into the engine compartment to see things. If you are not familiar with the style you have on the coach you might see if someone in the campground might help.

The other possibility is to stop at a Cummings shop and have it checked and ask if you can watch the process.

There is a continuous learning curve, but just knowing what to look for is always good.

Rich.

[manholt]

rwitt.

Do you down shift while climbing steeper hills? I found that it was hard to keep my rpms on I-5 in Northern CA. and Oregon while climbing, due to some "crazy" reverse slanted curves! Downshifting to 5 or 4 my speed up was steady.

Carl

[wolfe10]

Those hills outside of Branson are short, but quite steep. Sure, check for junk in primary fuel filter and look at boost next time you drive, but bottom line is they ARE very steep.

Been there done that.

[wildebill308]

We traveled south on US 65 to Branson, MO today towing a 2012 Jeep GC. As we got into the Ozarks we started really slowing down going up hills. It was doing fine on less steep hills, but slowed to 30-35 mph on the ones around Branson.

These are not like we are crossing the Rockies. Just wondering if anyone has any ideas.

Did you down shift to keep your rpm up? There is no coach I am aware of that will climb every hill without slowing down. On steep hills you will slow down.

"These are not like we are crossing the Rockies." You will find some steep hills around Branson. I have just returned from a trip east. You will find some amazing hills in the east. On the east end of The Great Smokey Mountain National park there is a road that has a 7 mile 9%+ grade that will rival anything out west. I think driving I-79 from Erie PA to Charleston is as challenging as anything out west.

I recommend keeping spare fuel filters with you as they can get clogged quickly if you have some bad fuel.

Bill

[hermanmullins]

Ron,

One thing I found when climbing steep inclines is to floor the throttle just as I come the the start of the hill. This get my RPMs and torque up for the climb. Also when in an area with lots of steep hills is to be sure you are out of economy mode.

Herman

[wolfe10]

Actually, in those steep, rolling hills, vary your speed A LOT-- on purpose.

Gain speed going down and "trade it" for elevation on the steep up-grade.

[rwitt]

Thanks everyone. I appreciate all the help. As for driving technique, I can say yes to all....... Down shifting, maximizing speed going down, flooring the throttle, etc. I just thought going down to 30-35 before the top was not good. I have been talking to some in the park here and they had the same experience. Just a follow-up question: if I have a dirty filter wouldn't it cause a power loss even when not going uphill?

[wolfe10]

Just a follow-up question: if I have a dirty filter wouldn't it cause a power loss even when not going uphill?

Actually, climbing a grade at Wide Open Throttle and high RPM demands the most fuel flow. So, this is where a restriction would first show up.

[wayne77590]

Hmm! I was taught differently. Typically I'm on cruise control coming to a hill. I'll press on the accelerator until I reach the throttle cruising speed and I take cruise control off. Never moving my foot on the accelerator and never increasing or decreasing throttle I let the RV do the work. It will automatically down shift keeping about 2000-2500 RPM and therefore keeping the temperature down. Yes, it slows down to about 45 mph and on a really steep one, 35 mph, but the temp stays below 210.

Been there done that on the Branson hill area. They are pretty steep.

[DaveAtherton]

rwitt,

I can pull information up on my Cummins Insite about low power ( will need model number ) ISL 400 What?
the Cummins ISL has a variable pitch turbo that returns a set amount of turbo gas into the intake of the engine. I
did see response with fuel filter dirty problem, than the turbo boost. the turbo boost is where problem located. How
the variable pitch turbo will work it has a sliding ring and a defusuer plate which controls turbo boost pressure. this
ring will move back and forth via of a electric actuator. this ring and latch operation gets carbon build up and sticky
movement. there is a warm up mode which cleans the carbon from this ring and latch assembly. sounds like a
clicking sound. this is a common problem with the variable pitch turbo setup. If cummins connects there Insite computer
into your system you will find inactive codes like fault code 2388 VGT Actuator Position Failed, Automatic Calibration-
Out of Calibration. in many times the code is inactive. fault code 2387 VGT Actuator Driver Circuit ( motor)- Mechanical
system not responding or out of adjustment. Some as simple as a wire connection to motor. last going with possible
wire connection dirty or loose or grounded. Fault code 2383 VGT Actuator Driver Circuit -Current below normal or open
Circuit. Again note: this controls your turbo boost on the ISL. Having a complete engine model and s/n would be
very helpful in helping you. Cummins ISL 400 HP. is a real good engine and a very high mile engine, but this one
area that will cause problems. Dave Atherrton Retired Cat Mechanic

[wildebill308]

When ever you talk to Cummins you will need your engine serial number. I would start a file with all your information as a quick reference list of serial numbers including your coach serial number, filters ect.

Bill

[rwitt]

DaveAtherton,

The information I have just shows Model # as ILS400HP. The SN is 46747274. Thanks

[DaveAtherton]

rwitt, looking over the information I posted above gives a good over view of what sounds like your problem.I would make

a suggestion if and when you have your motorhome looked at. your turbo problem is either caused by carbon buildup in

actuator housing. bad actuator motor. in many cases bad connection to motor. What cummins is going to tell you that

problems found in the actuator assembly. If this the case cummins has stopped selling the small parts to repair actuator

motor or little nylon gears inside on actuator housing. they will tell you that the complete turbo has to be replaced and

it is very costly. Again I would suggest getting cummins insite readout with print out of problem first. Once you can get

copy of ECM readout fault codes, if you would I can assist you once you have Fault codes in hand. I do have cummins

insite where I can look up fault code (.this varaible pitch turbo has caused problems ) but before you give a Ok for repair

work there is a plan B and will tell you why once we get fault codes. Dave Atherton Retired Cat Mechanic

[wildebill308]

^{I was re reading this thread. I don't think you have a problem 25-30 boost is about all you are going to get in a stock set up. Not picking on you because we all have to learn what to expect when driving. I think you are OK to go have fun.}

^{You might experiment with manual downshifting when you start to slow on a steep hill. Keep your rpm up to 2000-2200 this will also reduce your chances of overheating. The problem is the old weight to horsepower ratio. You are driving a big heavy coach compared to your car. By the way please add your coach to your signature it will help get better answers.}

^Bill

[DaveAtherton]

WILDEBILL is correct, being a mechanic for so many years a person gets caught up in solving problem deeper than what is

happening. Looking some info on a cumms Insite computer readout Diagonostic. just happen to run across something of

interest called Duty Cyle Monitor. In addition to diagonostic codes off engine cummins has a chart that tell Driver where the

engine rpm's high point and puts all info. on a chart. where I'm going on this on a ISL 400 the peak horse power and torque

will show percent of time at what rpm range and will tell Driver how he falls into correct Driving window. example the chart

will show advertised power rpm 2800, advertised power at rpm, peck torque rpm, peck torque at rpm. Note this is for a another

engine that I had my cummins computer on. To finish with my thoughts on this chart for the engine to have Max.power, the

correct peck torque is 1600 rpms and that would give driver 660 ft.lbs. of torque, on A ISL 400 peck torque at 1200 rpm will be

1600 ft.lbs of torque. Again have to agree with WILDEBILL do not think there is a problem, Again try to let motorhome just

lug down going midway into steep grade and you will see where the peck power will stay. Most of us have a trend to keep

downshifting to keep the rpm's higher around 1800 to 2000. Just go and have fun. If you are around the Quartzsite area in

the winter time I can put my cummins Insite computer on your engine and will print out the above information above because

it is on the ECM history. Putting all the thoughts on this forum, gives a person a real good over view from many different

directions to lean to. In most cases problems are minor in nature. I hope this will give you a better Idea on how a Diesel

engine gets peck power is on the reverse side or down side of the engine rpm's

Dave Atherton Retired Cat Mechanic

f

[rwitt]

Thank you Dave for the follow up. I hope you and Bill are correct and there really is no problem. I've had enough of those already on other things and we just started full timing. I sure don't need a bad turbo right now

[wildebill308]

When are you going to drive again? I recommend keeping your rpm up on a steep hill to keep your EGT temps and engine temps down. Do you have an EGT gauge? You told us what your boost was so you have a boost gage. I am a firm believer in knowing what is going on back there in the engine compartment.

Bill

[akadeadeye]

How do you check boost. I don't find a boost gauge on my dash.

Don

[wolfe10]

Don,

Very few motorhomes come with boost gauges. But most of the aftermarket monitoring systems do allow you access to that.

Silverleaf is kind of the top dog. I have a Scan Gauge D (about $170). Boost is one of the menu choices with both.

[wildebill308]

Brett do Silverleaf and Scan Gauge D allow you to monitor EGT?

Bill