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Scott, Driveability expert
Category: Dodge
Satisfied Customers: 1190
Experience:  Dodge,Chrysler,Jeep Master Tech since 92.ASE Master since 1990.Currently Dealer employed.
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Dodge: Dodge cummins 2003 has a fuel knock..slip..clutch..comes back

Customer Question

Dodge cummins 2003 has a fuel knock in it at a elevated idle 1000 rpm comes and goes have to slip the clutch and rpm will drop down to around 800rpm and go away if running down the road it will come and go if you ease into the fuel it will go away when let off the clatter comes back been to tree dodge dealer ships no one has a clue .
Submitted: 7 years ago.
Category: Dodge
Expert:  Scott replied 7 years ago.

Hello, Well sounds a bit tough, But I like tough ones. I think the best way to answer your question is to tell you how I would go about fixing your truck.And you may need to be pro-active with the Dodge store to get yours fixed. 1st concern is to duplicate the fuel knock at will. The Scan tool has the ability to electronically kill each cylinder . Once the knock is duplicated , I will take out cylinders one at a time untill I can pinpoint the one or two that make the most noise. I would then replace those injectors. I have also swapped the suspect injectors to a different cylinder to see if the knock follows the suspect injector. The fuel knock is caused by injectors that are damaged. They can be restricted or "sticky". If the noise goes away at this point. I will replace the fuel filter and recommend a fuel additive to help clean the other injectors and remove any moisture in the fuel.

I have also seen the injector pump cause a kind of knock when its installed in a way that causes the pumping chambers to be aligned with the lobes on the camshaft in a way that causes a slight bit of movement that translates into sound . This sound is most noticeable at idle and disappears just off idle. I repair this by moving the gear on the pump about 25 -30 degrees and retry it. This problem is more likely after a major repair where the pump gear has been moved. But I have seen a few that just get that click .

We have also had a fuel knock type noise turn out to be the first sounds of a piston starting to fail. Normal cylinders that fail are #5 or 6. So I really try and make sure that the noise is caused by a dirty /damaged injector and not a piston that has a plugged oil jet.I hope this info helps you get the engine properly diagnosed. If you need more info of help. Please reply, Regards, Scott.

Expert:  Scott replied 7 years ago.
Hello, Did you get the answer? Thanks Scott.

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