Engine Knock

D

Deputydog

Proud Fummins Owner
Joined
Jun 19, 2008
Messages
407
I removed my injectors the other day for a nozzle upgrade. Prior to that, truck was running great, purring like a kitten.

Installed injectors with new connector tubes and now I have a distinctive knock that I cannot seem to figure out.

This is what I have done and know. Truck does not smoke on start up or at idle. There is no haze while cruising. Runs very strong, rail pressure can get up to 25K easily. I put a snap-on scanner on it to electronically shut down each injector to see if the knock went away. The knock never changed and didn't go away as I shut each injector down. So I'm fairly certain its not an injector issue.

Everything was torqued to spec when it was reinstalled..

Any ideas?
 
If all I did was replace my injectors, and then developed a knock, I would feel quite certain that injectors are the issue.

Is it a heavy knock? or a tick?
 
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Snedge said:
If all I did was replace my injectors, and then developed a knock, I would feel quite certain that injectors are the issue.

Is it a heavy knock? or a tick?
Click to expand...

Its a heavy knock.

I'll hit the connector tube nuts again with the torque wrench.. The info I had called for 37 ft lbs.
 
How many miles on the truck? I'm just curious, with it being an 03, I was told I should replace full injectors and not put just nozzles, I have an 03' w/165k miles. Hope someone helps you with your problem.


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Im betting money on a nozzle. Replaced one on a friends truck a few weeks ago that had a loud knock at idle and increased with rpm's. Different nozzle fixed it. Only thing I could determine with the nozzle removed was the needle was very tight in the bore. Took several hard taps to get it out. There was alot of tarnish/discoloration, Im sure from some bad, poorly filtered fuel over the years.

Other than the knocking noise, the truck ran fine.
 
Deputydog said:
I removed my injectors the other day for a nozzle upgrade. Prior to that, truck was running great, purring like a kitten.

Installed injectors with new connector tubes and now I have a distinctive knock that I cannot seem to figure out.

Everything was torqued to spec when it was reinstalled..

Any ideas?
Click to expand...

Knocking at idle, only when you're on the throttle, or both?

Are nozzles larger or the same size? If larger, too much timing now?

Standard oops-questions:

You're sure you got 03-04 nozzles and not 04.5+ ?

Sure you have copper washers? None doubled up?
 
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WUnderwood said:
take the oil cap off when it's idling, and see if you have any blow by
Click to expand...

I have a light haze when I take off my oil cap, no noticeable blow by on the blow by tube though. That's acceptable correct? I am planning on installing my nozzles really soon.


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I'd say valve lash, but you can check by listening by your air cleaner. If you hear the knock through there louder than by the motor; it is most likely your valve lash. The good diesel shop around here says to set it while the truck is hot and a little tighter. I had the same thing going on after I changed my injectors. I took it to one shop and They told me I'd need a new head for $1500. I took it to Mumau Diesel and they put it on the computer then redid the valve lash hot for ~$126. I have had no problems since and would gladly drive the extra 30min to see those guys.
 
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