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Cat Man
Cat Man, Cat Engine Expert
Category: Construction and Road Equipment
Satisfied Customers: 8347
Experience:  I am ASE Master Certified.
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I have an 2006 peterbuilt 379 with c15cat I'm trying to

Customer Question

I have an 2006 peterbuilt 379 with c15cat I'm trying to figure what the problem my engine light is not coming on but my truck is lossing power and spitting out light blue smoke.... My truck act up when I shift out and go to the high side i loss power
Submitted: 2 months ago.
Category: Construction and Road Equipment
Customer: replied 2 months ago.
When I get an load on it... It like it needing more fuel
Expert:  Cat Man replied 2 months ago.
Thanks for asking your question. I will try and help you out.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. You may also have a problem with the turbo. It can have fin damage or excessive end play and cause low boost.Please let me know if you need more help or have more questions.
Customer: replied 2 months ago.
Will do bro... Thanks alot I will try and track it down
Expert:  Cat Man replied 2 months ago.
You are very welcome my friend. I am happy I could help.
Customer: replied 2 months ago.
I've done every step you've given me and I'm still have the same problem fuel pressure is good I've changed transfer pump out.. I've pulled off primer hand pump checked it... Disconnected primary fuel lines and put an site glass in the middle of both line to watch the fuel and test drove truck and it still done the same thing
Expert:  Cat Man replied 2 months ago.
Thanks for the information. Sorry you are still having trouble.How much fuel pressure did you have while drivng?
Customer: replied 2 months ago.
80 at idle and acceleration 100
Expert:  Cat Man replied 2 months ago.
How about while driving and the problem happening?
Did the turbo look OK?
Did the air to air cooler hold air?
Customer: replied 2 months ago.
it happens when I'm driving...... I haven't checked the turbo...... Air systems holding
Expert:  Cat Man replied 2 months ago.
Did you check the fuel pressure while drivng?
Customer: replied 2 months ago.
No sir I didn't
Expert:  Cat Man replied 2 months ago.
It's best to check it while driving under load. Fuel pressure can be good at low and high idle. Must maintain between 75-90 while driving.You should also check the turbo as well.If the fuel pressure is good while driving. I would check the return fuel line for restriction. Restriction can cause low power as well.

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