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cat c7 power loss- need suggestions

n4hwl
Explorer
Explorer
I am from Tennessee and have driven this motorhome about 39K during the last 6 years of so since I bought it. I arrived in Denver Colorado about 2weeks ago. I noticed a very noticeable decrease in power when I arrived. I took the motorhome to the local Transwest Freightliner dealer that is an authorized Cat repair facility. I now have a new turbo charger, and a completely new set of injectors and a new wastegate controller. I picked up the motorhome today with the assurance that everything was fine. Something is definitely still wrong . It has very little power on acceleration and really just lugs along until I can get up to about 2000 rpm. I know I am used to the power back at home under 1000 feet elevation and I am now in Denver at about 5000 feet but have a hard time believing that the severe loss of power is entirely because of elevation. I am taking it back to the Freightliner shop tomorrow.

The question is how much loss of power have you folks seen on a properly working turbo charged diesel at the elevations I am at here in Denver? I know I will see some but this thing is a real dog when starting off. I was going up a little rise from a stop light and had my foot to the floor and I did not think it was going to get above 1500 rpm and get out of first.

Any suggestions or comforting words would be appreciated.

Thanks

Stuck in Denver

Ken
2014 Tiffin Zephyr
27 REPLIES 27

Big_Katuna
Explorer II
Explorer II
I have your drive train. No check engine lights?
My suggestion would be to get the Silverleaf diagnostics. $300 which will pay back pretty quick in dealer code readings. Assuming you have a laptop. It tells you everything that's going on.
My Kharma ran over my Dogma.

AH64ID
Explorer
Explorer
n4hwl wrote:
Let me correct myself. I am not seeing any smoke from a standing start with my foot to the floor.

Ken


On more modern diesels you can have an airflow problem and not get smoke. The computer fuels based on boost, no fuel not boost.

It makes it hard to diagnose. Is the lack of boost from a leak or lack of fuel?
-John

2018 Ram 3500-SRW-4x4-Laramie-CCLB-Aisin-Auto Level-5th Wheel Prep-Titan 55 gal tank-B&W RVK3600

2011 Outdoors RV Wind River 275SBS-some minor mods

n4hwl
Explorer
Explorer
Let me correct myself. I am not seeing any smoke from a standing start with my foot to the floor.

Ken
2014 Tiffin Zephyr

tinkerer
Explorer
Explorer
I don't know what year your coach is, but there should be a turbo boost pressure readout in the instrument panel. My C7 has 25-27 lbs of boost at full throttle.

n4hwl
Explorer
Explorer
I would think that if I am low on boost pressure( Leak ect.) and my fueling is normal then I should be seeing quite a bit more smoke. I am not seeing a lot of smoke and am starting to wonder if I am getting enough fueling. Just guessing

Ken
2014 Tiffin Zephyr

noteven
Explorer III
Explorer III
Your turbocharged engine should "normalize" and not be affected by the altitude. Good suggestions above regarding low manifold pressure due to leak(s). Do you have a "boost" guage and is it in the normal range it runs when your coach was running properly?

path1
Explorer
Explorer
I now have a new turbo charger, and a completely new set of injectors and a new wastegate controller. I picked up the motorhome today with the assurance that everything was fine. Something is definitely still wrong . It has very little power on acceleration and really just lugs along until I can get up to about 2000 rpm.


(wide guess) Look for an air hose that didn't get put back on or is sucking air from atmosphere. Could be nothing more than a clamp that didn't get tighten.
2003 Majestic 23P... Northwest travel machine
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AH64ID
Explorer
Explorer
A failing pressure sensor, ambient or manifold, could work normal at your home elevation but throw the fueling off at higher elevation.

The freightliner shop should have the diagnostic equipment to look at sensor output.
-John

2018 Ram 3500-SRW-4x4-Laramie-CCLB-Aisin-Auto Level-5th Wheel Prep-Titan 55 gal tank-B&W RVK3600

2011 Outdoors RV Wind River 275SBS-some minor mods

Tom_Barb
Explorer
Explorer
While a$$ guess, blown intake gasket.
2000 Newmar mountain aire 4081 DP, ISC/350 Allison 6 speed, Wrangler JL toad.

FIRE_UP
Explorer
Explorer
Ken,
We just went through that section of Denver a few weeks ago. We have an '04 Itasca Horizon 36GD with the C-7 330HP CAT. We live in Lake Havasu AZ and, to the best of my rememberance, our coach performed in Denver, pretty much the same as it does in our home which, is not all that far above sea level. And, we're towing a 5300 lb. GMC Sierra 1500 4x4 truck. So, while you've had injectors, turbo, and waste gate have been changed, obviously there's something else wrong 'cause you're still experience a power loss.

It has been suggested that the fuel filter(s) be changed too. We kind of assume that, they or, it, has been changed, based on one or two filters since not all C-7s are created equal. Now, while I've been around diesels for most of my career life, (about 36 years total in the fire service), I'm certainly no expert. But, one component that we had go bad on several of our fire trucks was the CAC or, Charge Air Cooler or, another name is the Inter cooler. Those are mostly made of aluminum and, because of the structure around them, they can crack, in multiple places.

When that happens, you can have a ton of brand new turbo chargers and it won't do any good because, all the air your "turbo charging" is escaping out of the cracks or, crack, or hoses that attach the unit to and from the engine etc. And, you can have bad hoses or, broken clamps etc. Now, I'm not saying this is your problem. I figure those CAT techs pretty much know what they're doing and who am I to tell them what's wrong? But, it's a suggestion.

I don't know if you or, they, (the CAT techs) are near a dyno, it's possible that you may be able to tell where the problem is. It might help you and, it might not. But, we, in the FD, could see when the cab was tilted up and, the engine running, and the clutch fan turned off, that, just like spraying a soapy solution over an inner tube from a bicycle to find a leak, or pressurize a gas/fuel tank to find a leak, we'd spray the inter cooler and see lots of bubbles emanating from multiple places. It meant we were loosing lots of charged (pressurized) air and, therefore, lots of power. And boy, could we tell it.

Once the intercooler was either repaired or replaced, it was like a new engine had been installed. You see, sometimes those cracks or, breakages, happen over time and you loose the power, slowly but, do not really recognize it.

So, anyway, maybe some of this info will help. Let us know if it get's corrected so that others (including myself) will learn.
Scott
Scott and Karla
SDFD RETIRED
2004 Itasca Horizon, 36GD Slate Blue 330 CAT
2011 GMC Sierra 1500 Ext Cab 4x4 Toad
2008 Caliente Red LVL II GL 1800 Goldwing
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n4hwl
Explorer
Explorer
Bill thanks that helps. and yes fuel filter and air filter
have been changed. i did that before i took it to the shop.

Ken
2014 Tiffin Zephyr

Trackrig
Explorer II
Explorer II
We were up at Eisenhower Tunnel (just over 11,000'), Steam Boat (Rabbit Ear pass at 9,426') and Teton Pass (8,429' with 8 miles of 10% grades) earlier this summer and didn't notice a lack of power due to the elevation. We have a Cat C7, 350HP in a 2005 Fleetwood Excursion.

Bill
Nodwell RN110 out moose hunting. 4-53 Detroit, Clark 5 spd, 40" wide tracks, 10:00x20 tires, 16,000# capacity, 22,000# weight. You know the mud is getting deep when it's coming in the doors.

Twomed
Explorer
Explorer
Assume fuel filters have been changed?? No air in fuel lines??
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