Knocking

[Fieldoc]

I have a knock in my 03 that reminds me of when a lifter was sticky in my gas 350's. It is most pronounced when accelerating above 2000 rpm's more so if accelerating hard. Can barely here it under 2000 normal driving if can here it at all. Everything else seems normal, power, mileage 14.5-16 city {country} no smoke, starts well. Injector??????? Thanks. :confused: On edit, also does not seem as loud when engine is cold.

[More Power]

This sounds like normal pilot injection being reduced when the driver uses more power. Do a search for the keywords "pilot injection" here in this forum to learn more.

MP

[jbplock]

Here is a good description of Pilot Injection from a post by member Modified. (from What's this noise, not the idle tapping (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=3;t=005485))

"Diesel engine fuel injection systems that use a common rail system, as the Duramax diesel does, may or may not have what is referred to as pilot fuel injection at the lower engine speeds. Pilot fuel injection is defined as a pre-injection of a small quantity of fuel 5 to 20 crankshaft degrees before the main fuel injection. This pre-injection softens the main injection pressure rise and reduces combustion noise. At engine speeds above 2600 RPM, and a fuel quantity supply greater than 35 cu mm, it is necessary to eliminate pilot injection to meet emission requirements. When driving at or above these speeds, main injection combustion noise may be noticeable. It is normal and not harmful to the engine.
When traveling in 5th gear, the pilot injection to main injection transition is typically in the 136km/h (85 mph) range, however it may also be heard under heavy acceleration and when pulling loads up a hill during shifts at or above 2600 RPM. Customers that install the fifth gear inhibit switch, (ODLO), may encounter the fuel knocking of main fuel injection at speeds around 107 km/h (67 mph) in fourth gear between 2600 and 2700 RPM. This sound is considered normal and is to be expected."

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[Fieldoc]

Will the pilot injection start this soon as I hear this start around 2100-2200 rpm and it is not like diesel clatter, had a powerstroke previous to this and a 6.5 but more like I said before as a sticky lifter single not plural. Just trying to clarify and wondering if should get looked at or leave alone and drive it? Thanks. :confused: I tend to forget to much. Caan also just hear it when set at cruise around 70-75 mph.

[ 02-05-2005, 03:20 PM: Message edited by: Fieldoc ]

[madmatt]

starting at that low of RPMs I may suspect a injector sticking open slightly. I get your dealer to check it out. There is a bulletin describing this concern and how to diag it. Your dealer should be aware of it.