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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3304
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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I have a 1998 Kenworth Cummins N 14 select plus engine, it

Customer Question

Customer: I have a 1998 Kenworth Cummins N 14 select plus engine, it has excessive fuel on # ***** cylinder injector and ecm has been replaced what else could cause this problem ? Compression is good.
JA: Thanks. Can you give me any more details about your issue?
Customer: Overhead has been run more than once. It puts so much fuel into the cylinder it literally blows raw fuel out of exhaust port , and has excessive white smoke ? Could it be something in wirung harness ?
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Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 1 year ago.

My name is ***** ***** I will assist you.

Have you replaced the injector and harness? When you replaced the ECM, did you use new programming or the old programming in the ECM?

Have you changed the cam sensor?

These are the items on the top of my head that could create the condition.

One last is you may have a dead cylinder. I would do a compression test on the cylinder for if you have bad rings on that cylinder, the compression is not building up and creating combustion in that cylinder. You might have the need for a overhaul on your hands.

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Customer: replied 1 year ago.
far you have not told me anything that I have not done, Cylinder has plenty of compression, we installed new injector. ECM is reman which was programed to my truck. I am wondering the wiring harness has not been changed I am concerned it might be the wiring harness. How fairly common is that ? From what I can tell the fuel circuit is not closing on that cylinder.
Expert:  Jeremy replied 1 year ago.

Very common. The harness will get oil in it and will "push" oil and ground out from the heat of the engine and the expansion of the copper wiring. When the engine cools, the harness cools and allows a small amount of oil in at the crimps. Over time, the harness will short out and not allow the electrical pulses, which are in milliseconds. The ECM doesn;t send power. It has constant power. It sends ground. So if there is resistance in the ground, it will keep the injector on fire mode.

Electricity works like water in how the electrons move. If you put debris in the river, it slows the water down. Same with current and fluids. If you have something that conducts electricity like fluids, it will slow the pulses down.

I would definitely change the injector harness out. They are so common of causing issues that Cummins has them in stock all the time. I wouldn't be surprised if they have 3 or 4 on the shelf. I do 3-4 harnesses a week, especially on older engines.

Expert:  Jeremy replied 1 year ago.

I see you viewed this and this is still showing as a open question due to no positive (3 stars or more) rating.

Did you still need assistance with this?

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