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Robert
Robert, ASE Certified Master
Category: Dodge
Satisfied Customers: 4275
Experience:  Dodge Master Certified, Dodge Sprinter Certified
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I have replaced my injectors all 6 twice.in the last 2

Customer Question

I have replaced my injectors all 6 twice.in the last 2 months now just last week I hear a knocking sound but at idle it's not there until u put a load on motor or in the range of 1600 rpm until 2200 then u don't hear it.
Submitted: 1 year ago.
Category: Dodge
Customer: replied 1 year ago.
the valves have been check .the new injectors have been removed and re tested all good .need help .
Expert:  Robert replied 1 year ago.
Hello, welcome and thanks for asking your question. My name is***** a Certified Auto Technician with 27+ years experience. I will do my best to assist you. please keep in mind that I may need to ask questions of you before I can answer. When you reply please feel free to add as much detailed information as possible pertaining to your concern.
What was the original reason for replacing the injectors?
After being replaced, what was the reason for replacing them a second time?
How many miles are on your truck?
Have you ran the "Blowby Test"?
Keep me posted...
Thank you,
Robert
Customer: replied 1 year ago.
No blow by truck has 294000 first reason hard to start and haze at tail pipe second was new injector went out lots of white smoke.
Expert:  Robert replied 1 year ago.
Ok, What procedure did you use to check for blowby?
Other than the knock, does it run good?
When cold starting it, does it start quickly and idle smooth as soon as it starts?
Keep me posted...
Thank you,
Robert
Customer: replied 1 year ago.
It starts right up with a slight vibration on idle and as u give it fuel it goes away until 1500 or so it come back and worse at 1900 until 2200
Customer: replied 1 year ago.
As for blow by the shop check it .I can not tell u how .as u push the throttle it response like it should with no hesitation. Please respond asap so I can fix it in bad need of this fixed
Customer: replied 1 year ago.
Hello u there.
Customer: replied 1 year ago.
Can u give me a direction. ...
Customer: replied 1 year ago.
Hello
Expert:  Robert replied 1 year ago.
Hello, sorry for the delay. Was offline for a while...
From all that you describe, it leads me to believe that you may now have a problem with one of the cylinders. The clue that one of the injectors failed and caused white smoke leads me to believe this. What can happen when this occurs is that one of the cylinders can run too hot when an injector fails, this can cause piston and cylinder wall damage. The other clue is that when you start it it runs a bit rough.
I have an easy way for you to check for blowby yourself.
This must be done on a cold engine.
On the first start in the morning, before starting it, remove the oil filler cap and leave it off for the rest of this test. Go over and start the engine with the oil cap off. Quickly go out and look for smoke puffing out of the oil fill cap. IF you see puffs of smoke coming out, that is signs of excessive blowby. Another test is to rest the cap over the fill hole, if the pressure blows the cap off the opening, there is too much blowby. If this is the case, there is internal engine damage and engine will need to be torn down for rebuild or replacement...
Here are a couple videos showing this simple test:
The first one is a pass, no excess blowby on this test -->>
Click here to Visit
This second test is a fail, note lots of smoke out the fill hole...
Click here to Visit
If yours is more like the second video, you will need to tear down the engine for internal repairs....
Keep me posted and let me know if you have additional questions...
Thank you,
Robert
PS - I also need to let you know that my responses may be delayed because I may be helping another customer, or I may be temporarily offline. Your understanding is greatly appreciated.
Thank you...
Robert
Customer: replied 1 year ago.
Ok did the blow by test and it pass no blow by . Here is another symptom if u let the truck parked for a day the knocking noise is not present until it warms up .it's not loud knock but u can feel it in the stick shift. Starts around 1300 to 1500 then u get to 2200 it's almost not noticeable. I have even drop the transmission to see if it was that.
Expert:  Robert replied 1 year ago.

This all sounds like a possible fuel knock. Usually caused by a faulty injector. Where are these injectors being purchased at? Some remanufacturers are inferior when it comes to Cummins injectors. I recommend the Dodge Dealer or Cummins directly. I have had mixed results from injectors from other sources....

Keep me posted...

Thank you,

Robert

Customer: replied 1 year ago.
Ok i will take it to a cummins dealer
Expert:  Robert replied 1 year ago.

____________________________________________

If you need additional information, don't hesitate to ask. If I have answered your question, Please kindly "Rate" my service, it is greatly appreciated.

Thank you and thanks for asking your question!

Robert

Customer: replied 1 year ago.
Ok so I tore down the motor and stared testing the injectors with the ohms first one was at 3.0 and the rest at .06 so I replaced the injector but I rechecked the ohms still there so we changed the ecm well still the same so we start to check the internal injector harness and it's seems fine so we go past the connection and we find a repair so now we get a 1.5 reading and come back to the harness and best we can find is the harness is bad new one order find out tomorrow
Expert:  Robert replied 1 year ago.

Did you check the injector resistance directly at the injector also?

Let me know what you come up with on the harness...

Thank you,

Robert

Customer: replied 1 year ago.
with the wire off . It was .06 and with the wire on the first one u can fill a small shock if u touch the top of the leads on one side. On the one that's higher
Expert:  Robert replied 1 year ago.

You shouldn't feel a shock with the ignition off. IF this is the case, you may have found the problem. Hopefully replacing the harness will solve the issue...

Keep me posted...

Thank you,

Robert

Customer: replied 1 year ago.
Well I replaced the wire and still not fixed so. I'm telling u what I'm doing but yet have heard from u of what it might be .
Expert:  Robert replied 1 year ago.

If you are still getting 1.5 ohms on that injector, measured directly on the injector prongs, it means that injector is bad also. The spec for injector resistance is greater than zero ohms and less than one ohm. .3 to .7 is the "Normal" range that I always find on good injectors.

Replace any injectors that are out of this range.

If all injectors are good electrically, you will need to run an injector kill test using a scanner in order to pinpoint which injector is causing the fuel knock, once isolated, replace that injector...

Expert:  Robert replied 1 year ago.

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Customer: replied 1 year ago.
If u remember I took all injectors out and had them check .so it's not the injectors for sure.
Expert:  Robert replied 1 year ago.

Having the injectors bench tested is not always a foolproof method of testing. The best test for a fuel knock concern (if in fact this is what it is) is to run the injector kill test. If you kill an injector and the fuel knock goes away, chances are high that that injector is bad and you will need to replace that injector... Keep in mind that there still could be cylinder damage if the affected cylinder was overheating.

I'm still leaning towards an injector because from what you stated, the blowby test passed, although this is not a foolproof test either. To find out if the knocking is caused by a bad piston, another test you can run is a compression test. Anytime a cylinder overheats due to a faulty injector chances are high that piston and cylinder damage can occur. The compression test will be a surefire way to determine if there is any piston and cylinder damage...

Customer: replied 1 year ago.
I'm running out of money to find problem on this truck .
Expert:  Robert replied 1 year ago.

Since the injectors are all new, it shouldn't cost any additional for any new injectors as the replacement injectors should have came with some sort of warranty. At least 90 days. Most parts are warrantied for a year if purchased from the Dodge Dealer.

____________________________________________

If you need additional information, don't hesitate to ask. If I have answered your question, Please kindly "Rate" my service, it is greatly appreciated.

Thank you and thanks for asking your question!

Robert