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I have a C15 Acert MXS that has low power, low boost and…

I have a C15 Acert...
I have a C15 Acert MXS that has low power, low boost and high egt. Seems to get worse the longer the truck runs. Truck has been to a Peterbilt dealer and can't find any boost leak.
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Answered in 8 minutes by:
6/22/2018
Technician: Cat Man, Cat Engine Expert replied 4 years ago
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 10,344
Experience: I am ASE Master Truck Certified.
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Thanks for asking your question. I will try and help you out.
Does the yellow check engine light come on?
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Customer reply replied 4 years ago
No check engineEngine runs really smooth except for low power.
Technician: Cat Man, Cat Engine Expert replied 4 years ago
Thanks for the information.Since the check engine light does not come on, I would suspect 1 of 2 things are causing your problem.The first is low fuel pressure. If there is a low fuel pressure problem, the check engine light will not come on and the engine will have low power. Your engine should maintain a fuel pressure between 75 and 90 psi. There is a plug beside of the secondary fuel filter that is used to check the pressure. If it is low, I would first try the fuel filters if you haven’t already. If it is still low, you may have a failed fuel pressure regulator, which is located underneath the bottom of the filter housing. I have replaced a ton of these for low fuel pressure. It is kinda a known problem. You could also have a weak fuel transfer pump or restricted hand primer pump, if your engine has one.Second I would suspect you have a low boost condition. This can be caused by a leak in the air piping or air to air aftercooler on the truck. I would first inspect all of the piping to see if there is a hole in any of the rubber boots that hold the pipes. From there you may want to cap off one side of the air to air cooler, and pressurize it. They have been known to crack and leak and cause low boost.Please let me know if you need more help or have more questions.
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Customer reply replied 4 years ago
The truck did have low fuel pressure that was fixed by the Peterbilt dealer I took it to, new filter base, fuel line, regulator and filters. They also pressure tested the CAC and it passed with no leaks. I also replaced all the boots. This motor has the 550 heavy haul program and when the motor is hot will barely make 40psi of boost.
Technician: Cat Man, Cat Engine Expert replied 4 years ago
Thanks for the information.
Has the fuel pressure been checked while driving under a load?
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Customer reply replied 4 years ago
No they only checked it at idle and high idle.
Technician: Cat Man, Cat Engine Expert replied 4 years ago
It’s best to check under load while driving.
I’ve seen it good at high and low idle. But be low on the road.
If it’s good on the road. Between 75-90 psi. And the cooler is new, and the turbo is ok.
All that’s left is a plugged muffler. Restricted fuel return line from the engine. Or worn injectors.Please reply back if you need more help or have more questions. I am happy to assist.
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Customer reply replied 4 years ago
I will check the fuel pressure. I still have a suspicion it may be a turbo problem, they were checked by removing the intake and exhaust and the bellows but weren't completely removed from the engine. It also seems that there is a slight howeling noise from them that just doesn't sound right.
Technician: Cat Man, Cat Engine Expert replied 4 years ago
Sounds good. Yeah if there is a turbo noise it may be a turbo.
Let me know what you find.
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Customer reply replied 4 years ago
Okay, thank you
Technician: Cat Man, Cat Engine Expert replied 4 years ago
You are very welcome my friend. I am happy I could help.
Cat Man
Cat Man, Cat Engine Expert
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