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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8419
Experience:  I am ASE Master Truck Certified.
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Hey cat man I In have a 3126 with a no start in the morning

Customer Question

Hey cat man I In have a 3126 with a no start in the morning hit it with either and it will start rest of day started fine no check engine light no code's I have changed high pressure pump and check valve in back of head and ipr valve to no luck any advice would be great thanks
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 1 year ago.
Hi. Thanks for asking your question! I will try and help you out.
When the engine does start on ether. Does it run a little rough like it has air in the fuel? Or does it run good?
Customer: replied 1 year ago.

Yes runs a little rough then clears out

Expert:  Cat Man replied 1 year ago.
Thanks for the information.
Normally that's a sign of fuel leaking down from the head overnight. I have seen this many times.
So you have replaced the regulator on the back of the head and the fuel pump?
Do you know if there were any codes in the ECM?
Expert:  Cat Man replied 1 year ago.

Hey Anthony.

Most often the regulator and the fuel pump are the cause of fuel leaking down. But if you have changed the regulator and fuel pump, and there are no codes. I must next suspect the engine speed timing sensors. I have seen them cause a hard start before.

The engine has 2. One is the primary start sensor and the other is the primary run sensor. When the lower primary start sensor is faulty, It can cause hard. To confirm, I like to check AC voltage to the injectors while cranking. You should have 20-40 AC. If you do not, I would suspect the engine speed timing sensors. IF you do have 20-40 AC, Then I would suspect a fuel supply problem. The engine needs at least 25 psi to start. I would put a psi gauge on the system to check the fuel pressure.

Please reply back if you need more help or have more quesitons. I am happy to assist.

Expert:  Cat Man replied 1 year ago.
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.

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