Engine/Transmission (1994 - 1998) 1997 Model year w/a knock????

[Greenleaf]

A friend stopped in at the garage with a 1997 3500 that has a knock only with medium/heavy loads and at 2/3rds to wide open throttle. . Also has some light blue smoke when knocking is heard. Could this be an injector acting up????



Operates normally otherwise. Sounds good @ slow idle speeds. Pulls hard too. The engine is 100% factory stock w/106,000 miles. Manual transmission. He said this began a little while ago. Overflow valve looks good... ... I guess



Thanks for any tips.



Scott

 

[budctdca]

I would check your timing, seems to me this might be a good place to start, along with fuel filter, fuel lines, and OV valve. The P7100 pumps are very sensitive to variations in fuel pressure.

One question... how loud is this knock? Could it be in the injection pump, or does it sound like an engine knock?

 

[blacksheepdiesel]

Greenleaf,



Does the frequency of the knock match one firing event, several, or all?



Trent

 

[Greenleaf]

Them are good questions. I don't know if I can anwser them.



The knock is comming the engine and I ***think**** it's related to one firing event. Maybe I should check the supply pressure... ... ... ... I didn't think the timing would/could change by it'self. Looks like I need to investigate further.

Thanks for the tips.



Scott

 

[blacksheepdiesel]

Greenleaf,



One can investigate by getting the engine to knock, then slightly loosening the injector lines slowly one by one, retightening before moving on to the next one. When the knock stops you have found the culprit. At that point remove the injector and have it tested. Heck, why not remove all 6 and have tested!?!?



WARNING!!!! Be extremely cautious while perfoming the above procedure. Fuel is under ultra high pressure and can easily penetrate the skin leading to death.



Happy diagnosing!



Trent