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We have a 2010 Kenworth T660 with a Cummins ISX 450. It is…

We have a 2010 Kenworth...
We have a 2010 Kenworth T660 with a Cummins ISX 450. It is a former Conway fleet truck. According to the Cummins techs when we plugged to the computer, the engine is running like a top, not a code to be found. The engine is set at 450 hp (max) but is only able to push out 401. The fuel mileage is horrible and inconsistant, along with a hill pull. Sometimes we can pull very well and others, we down shift like crazy. The fuel mileage fluxuates from 4.6 to 6.3 mpg.

Need an answer. We just had a tune up, new air filter, over-head, grease job, and fluids changed. We have talked to 5 mechanics and heard a lot of possibilities. Help!!!
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Answered in 11 hours by:
11/17/2012
Technician: cumminsdr, Mechanic replied 9 years ago
cumminsdr
cumminsdr, Mechanic
Category: Medium and Heavy Trucks
Satisfied Customers: 4,463
Experience: All types of Cummins applications
Verified
Hello and welcome to Just Answer! I would be more than happy to assist you today.What is the engine serial number. How are you getting your HP output reading On a dyno? How many miles on the unit.
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Customer reply replied 9 years ago


All of the numbers given to you are directly from the computer read-out when the Cummins tech pluged into the ECM. The truck has 633,000 miles on it. Everything is stock. Engine serial number is XXXXX

Technician: cumminsdr, Mechanic replied 9 years ago

The ecm will not tell you how much HP you are putting to the ground, only a dyno run. I will .. I see the ecm was just updated, That is good, Normally when a fleet has the unit they make changes in the ecm to their likings, You will have to get the ecm Image printed out and have a Tech verify all info is correct and not modified. The features and parameters are the item that need to be checked, It consists of tire rev, tire size, gearing, ect. Pretty much the personality of the unit that the engine is in. If all is correct the engine will run at it's best in regards XXXXX XXXXX econ. But there are several factors in the fuel econ such as driving style,loads,driver habits,environment ect.

My suggestion to you is have your tech install a Power spec template in the ecm. They will know what i am talking about. It changes some parameters and optimizes performance in some cases.Fleets sometimes use it in all their units but it is a new procedure.

Also the injectors only have a life span of 500k miles and cummins recommends overhaul intervals between 500-700k miles, so you could have some other issues in the works too .

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Technician: cumminsdr, Mechanic replied 9 years ago

I see what they saw The calibration they did in Denver is what i have highlighted Your engine is rated at [email protected] but Governed at [email protected] the only way to change that for more power is to have them find a calibration that suits your needs. This was done for the fleet of units. That is how they operate. Have they run on a dyno and get the TRUE horsepower to the ground that is the only way you will know what output you have.

 

graphic

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Customer reply replied 9 years ago

We took this truck to the cummins tech. He looked at all the parameters for this truck. He told us that all of the parameters are set to optimum. According to him, there is no way to turn up the power or get any better fuel mileage. He did express that there is something wrong with the truck, inconsistancy with the fuel mileage (4.6 - 6.4) and random dropping of pulling power on a hill. The style of driving and environment have all been pretty much the same. We have spoke to many people and everyone tells us that the fuel mileage should be at least up to 7.0 to 9.0 with this truck and this engine.


 


As far as injectors, the engine has not shown any symptoms of any injector issues at all. Every mech or tech we have talked won't touch it until the ecm shows a fault code or told us it would be a waste of time. Everything is electronic and no one can diagnose anything without a code. And every mech or tech has their own theory on what is causing all of this.


 


Also, as far as an over-haul, how does the NTP warranty have an effect on this? Will they do an over-haul?

Technician: cumminsdr, Mechanic replied 9 years ago

If your getting 9 MPG Cummins would want that eng back! Avg is 6, No warranty will pay for an overhaul unless There was a failure that your warranty covered as I see all the extended warranty for this engine expired at 500k miles, Now you may have bought more at time of sale but read it close. As for the injectors you have an Cm871 engine and these injectors are mechanical NOT electronic so tell me how will you get a fault if they fail mechanically? The only code you may get is a 951 for a cylinder imbalance (sometimes).But if the injectors are not spraying fuel correct you could be wasting fuel. If the injectors were electronic they will still fail mechanically and not throw a fault. So their theory of wasting time is not true. They can up rate the HP as long as it is within the engines CPL rating and sometimes they can change the CPL to work with the parts in the engine. I don't have that program here or i could show you.

cumminsdr
cumminsdr, Mechanic
Category: Medium and Heavy Trucks
Satisfied Customers: 4,463
Experience: All types of Cummins applications
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