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I have a cat c12 I have a issue where it sounds like I have…

I have a cat c12...
I have a cat c12 I have a issue where it sounds like I have air in my fuel things I done replaced all fuel lines suction and return fuel regulator transfer pump fuel lines from pump to ecm fuel lines from ecm to filter housing hand primer pump all injector o rings all o ring in fuel rail had a guy tell me I had bent valves changed for nothing 3 sets of fuel filters
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Answered in 5 minutes by:
1/15/2018
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 9,458
Experience: I am ASE Master Truck Certified.
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Thanks for asking your question. I will try and help you out.
Can you elaborate on your question please?
When you say It sounds like you have air. Do you mean you have low power?
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Customer reply replied 7 months ago
Power is fine i can go threw the low side never break up soon as I get on high side it breaks up in 7th gear acts as if it's not getting fuel
Thanks for the information.
Has the fuel pressure been checked while driving?
Does the yellow check engine light come on while driving?
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Customer reply replied 7 months ago
I put a gauge on but don't know how trustworthy it is but it reads about 85 at idle but as soon as you rev it goes past 120
Customer reply replied 7 months ago
Haven't seen a check engine light truck is old might not work
Thanks for the information.
120 is too high. It should remain between 70-90 psi at all times. If there is a return line restriction. It can casue low power and high fuel pressure.
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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 7 months ago
I replaced all of those things I started with fuel filters the fuel regulator then transfer pump then fuel lines hand primer pump then injector o ring then fuel rail orungs I do notice that my return pressures going into tank is more less a thin stream that's not strong
Customer reply replied 7 months ago
Turbo sounds strong
Thanks for the information.
If your turbo has a wastegate. It could be sticking or leaking.
You could also have a leak or crack in the charge air cooler.
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Customer reply replied 7 months ago
Will that make it sound like I'm running out of fuel
Customer reply replied 7 months ago
I run straight pipes so you hear it
it will.
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Customer reply replied 7 months ago
you saying I'm having a air issue from the turbo
A possibly low boost issue with the turbo.
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Customer reply replied 7 months ago
A couple of weeks ago the airline that goes from to intake to the air compressor had came off and it made a weird noise after it did I don't know if that's something strange
Customer reply replied 7 months ago
How certain are you on the issue of the turbo I spent a lot of crazy money in the last month trying to get this truck back together
I just know if there is no light and low power. I always find low or high fuel pressure. Or a leak in the air system or faulty turbo.
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Customer reply replied 7 months ago
That's the thing I really don't have low power my power is fine it's just hesitant but it still picks up speed normally it just cracks and sputter and then it'll go
I see. Normally when you have a fuel pressure issue or turbo and air issue. You have low power.
Since you do not have low power. I must suspect an injector or injectors issue.
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Customer reply replied 7 months ago
Not giving any codes had technician ride with me gave a code for2 solenoid change injector still do it
your getting a code for number 2 injector?
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Customer reply replied 7 months ago
I haven't put back on computer
Customer reply replied 7 months ago
After I changed it
I see. Sounds like an injector issue.
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Customer reply replied 7 months ago
Wouldn't a injector do it all the time
Customer reply replied 7 months ago
Soon as I put the computer it shows no fault codes
Customer reply replied 7 months ago
Computer shows no codes
No not always. I have seen them be intermittent
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Customer reply replied 7 months ago
how do I figure that out
Sometimes you can run a cylinder cutout to isolate and find the problem injector.
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Customer reply replied 7 months ago
This the thing all injectors was rebuild warranty just ran out
Customer reply replied 7 months ago
Does the fuel return to the tank at 70 to 90 psi
No. The regulator holds the pressure between 70-90. After the regulator the pressure is much lower.
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Customer reply replied 7 months ago
What are the chances of my spring weaking and not holding enough tension would I have more pressure are trouble when sat for a while and not starting
Not common to have spring problems on injectors. Normally problems with injectors are internal.
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Customer reply replied 7 months ago
No I'm talking about the fuel pressure regulator spring
A spring problem can cause that.
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Customer reply replied 7 months ago
I stretched the spring and it got worse it's doing it on the low side now
I’d try replacing the regulator
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Customer reply replied 7 months ago
Do secondary fit filter housing have something to do with it could have been a pressure regulator be sticking on the inside of their

You could have a cracked filter housing. I have seen that before.

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Hey. I just wanted to see how things were going. Please let me know if you need more help. I am happy to assist. If my information was helpful, please leave a good or higher rating so that I receive credit. Thanks.
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 9,458
Experience: I am ASE Master Truck Certified.
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Cat Man and 87 other Medium and Heavy Trucks Specialists are ready to help you
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Customer reply replied 6 months ago
Was sick I changed the filter housing it got a lot better but still hiccuping in 9th and 10th gear I changed regulator spring but I didn't change the fuel regulator I noticed that the fuel regulator in the old filter housing was jammed in there I put it in the new one and it you could put it in easy slide it and it and turn it upside down and it slides back out should I have change the regulator to get rid of the the last of that air
Thanks for asking your question. I will try and help you out.
Yeah I would change it.
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Customer reply replied 6 months ago
Can't get one till monday
10-4. I’m glad the problem got better.
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Customer reply replied 6 months ago
Noticed that the return pressure in the tank is a lot higher it's making bubbles in the tank from stream pressure and regulator had some suff marking on it think this should solve it
i agree.
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Customer reply replied 6 months ago
Let you know monday
10-4
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Customer reply replied 6 months ago
Changed the regulator no change in it but the filter on side of frame is not filling up with fuel normally when lossen fuel would overflow its under half full could i have brought a faulty transfer pump and will cat warranty cover it
Thanks for the information. Yes it’s possoble the new pump is bad. It has a one year warranty.
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Customer reply replied 6 months ago
Ok paid for new pump not problem answer this if you over adjust the injectors when running rack could that give me and issue
Customer reply replied 6 months ago
I turned the adjustment more than it requires to get more fuel
Thanks for the information. Actually turning the adjustment has no affect on more or less fuel delivery. But an improper adjustment can cause the engine not to run correctly.
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Customer reply replied 6 months ago
I have a gauge on it pressure at idle is a bouncy 75 to 80 put max load it goes past 110 plus
Customer reply replied 6 months ago
I have a gauge on it pressure at idle is a bouncy 75 to 80 put max load it goes past 110 plus what cause that
That pressure is good.
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Customer reply replied 6 months ago
not a fuel pressure problem
Does not look like it.
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Customer reply replied 6 months ago
Where do I look now
Customer reply replied 6 months ago
Go back and reset rack to factory specs
I would.
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Customer reply replied 6 months ago
Previously I had issue with it cracking and popping and blowing white smoke you helped on that find out it was a Jake brake issue back Jake off truck ran perfect explain in dummy terms how to do Jake setting with filer gauge
It’s not hard. Just insert the feeler gauge under the Jake foot and adjust til there is a slight drag on the feeler.
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Customer reply replied 6 months ago
What's the set point for gauge
What’s the engine serial number?
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Customer reply replied 6 months ago
9ns03052
For a 9NS it should be 0.040
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Customer reply replied 6 months ago
I talked to a old school mechanic and he told me to put some additive in and I finally notice improvement tomorrow I'm draining that fuel and putting fresh fuel back he says I might got bottom of tank fuel and didn't know it and the cold weather made water and it's trying to burn the fuel but the water mixture causing compression issues sounds about right
water in the tank can casue issues like this.
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Customer reply replied 6 months ago
No change in it I did pull a load with it got up to 75 at one point but bucking piping along the way empty would just pickup speed faster
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