600 Injector/Knock Question

[ceastmen]

I realize there are a hundred possible effects of a bad injector, but does it cause a knock? How does one distinguish a knock form regular diesel "clack clack?"



I have a sound at around 1750 - 2200 in my 04. 5 CTD 600 that sounds like a gasoline engine knock, I may be wrong but it sounds like a knock.



Could this more pronounced noise be an effect of the fueling up process?



Thanks!

 

[klenger]

If you are referring to the pinging sound that the 600's make under mild accelleration, it's normal. My brain has tuned the noise out already and I don't even think about it. Speculation is that the noise is from the 3rd injection event added with the 600's for polution control.

 

[hotram03]

my 03's pilot injection has gotten alittle louder with some miles, but hey its a diesel their really not supposed to be quiet after all huh LOL.

 

[Prairie Dog]

Yes, a bad injector can cause a knock that sounds but doesn't act like a bad rod bearing. A loose injector can cause it too.



Scott

 

[ceastmen]

Klenger,



That is the knock I'm talking about, but how do you know it's normal?



It doesn't seem to affect power, or at least I can't tell having nerver driven the truck without the knock, but it does sound like pre-ignition in a gasser. Pre-ignition in gassers is the kiss of death if allowed to continue.



On an unrelated dealer visit, during a test drive to correct the alignment, the dealer tech told me the ping or knock was normal, but I tend to take what they say with a grain of salt.



Just thought I'd query this forum to see if anyone has real evidence or hard fact about what causes it.



Thanks.

 

[klenger]

We have determined it's normal because all of the 600's are doing it. Not very scientific. Someone smarter than me had a better explanation.

 

[FlyBoy007]

As I understand a diesel can not pre-ignite as there is nothing in the cyl. but compresed air until the engine is ready, then it adds fuel to the the air for the ingnition.



I also have a sound like you decribe under the same conditions, I think the engine is so quite at idle that we forget its a diesel and the sound is... well different.



just my $. 02

 

[Prairie Dog]

Mine had the knock, I could even feel it in the throttle. After about 10k it just went away on it's own.

 

[dieselpilot1969]

what would make one of these trucks backfire under hard accell (weak lift pump maybe)

 

[Jumbo Jet]

I don't know how much difference there is in a 600 and the 305 HP '04 , but my truck had a serious knock. The #5 injector was remaining open. It was replaced and the serious knock went away. When I say serious, I mean like a rod knocking.



My fuel economy and power has returned.



Another TDR member had the opportunity to ride in my truck and he heard the serious knock.

 

[mattymac]

QUOTE: what would make one of these trucks backfire under hard accell (weak lift pump maybe)



Diesels dont backfire, they missfire from lack of fuel supply that is probably coming from a weak lift pump. People running the TST box on higher levels without a pusher pump of some kind would have this happen due to the higher demand for more fuel.

 

[ceastmen]

FlyBoy007,



I've heard a leaking injector can cause pre-ignition because it leaks fuel into the cylinder prior to its scheduled injection event.



I've not had first hand experience with a leaky injector so please take the prior statement with a grain of salt.



So lets say the injectors are leaky and causing a knock. I would tend to think the leak would get worse with more fuel pedal - line pressure goes up with throttle position - so would this be worse at more throttle? Anyone have this experience?



Thanks in advance!

 

[rbattelle]

Pinging or knock can be reduced by increasing RPM, which increases piston speed and will tend to reduce the knock tendency. Given this fact, if your ping/knock is occuring only in a specific RPM range, it seems logical to me that you've got something wrong with your fuel delivery system.

 

[rbattelle]

Originally posted by Jumbo Jet

I don't know how much difference there is in a 600 and the 305 HP '04 , but my truck had a serious knock. The #5 injector was remaining open. It was replaced and the serious knock went away. When I say serious, I mean like a rod knocking.



My fuel economy and power has returned.



Another TDR member had the opportunity to ride in my truck and he heard the serious knock.

]



Jumbo, what RPM range was the knock occuring?

 

[rbattelle]

Ceastmen,

You know, something else just occurred to me. Try a cetane booster before doing anything, and see if that cures the noise. It's cheap, and will help narrow down a mechanical or fuel problem.

 

[Jumbo Jet]

Jumbo, what RPM range was the knock occuring?

Off idle to about 1200 RPM knock was very noticeable.



Fuel economy was down about 15%.



Power was down, but I couldn't really measure it. I know since I have had the injector replaced, the truck doesn't lose as much speed pulling my 5th wheel RV up the same hills.

 

[rbattelle]

I've got a distinct knock in the same range. It only occurs under light throttle, and disappears under heavier throttle. It only occurs when the engine is hot. And, it has come and gone periodically over the year I've owned the truck. Fuel mileage is normal (18. 5 lifetime average), power seems to be normal. I am reluctant to take it near the dealer.

 

[JRG]

Mine is exactly the same as rbattelle.



JRG

 

[Scooby]

I have it also. I notice it around 1500-1800 rpm mostly. It sounds like cheap gas in a gasser engine going up hill!



I added some cetane booster and can't really notice a difference. The pinging/knocking goes away after 2000 rpm. I don't like how it sounds, but I guess it's normal??



I'll have the dealer check it out when I bring it in. (I have other small annoyances - i. e. bulb out, weather stipping tearing on A pillar, etc... )



I swear I'm starting to hear a little whine from the transmission or rear end at 25-40 mph (especially at low rpm... . ie in 4th gear)

 

[rbattelle]

Scooby,



What you're talking about is what I would call pinging, and I believe is completely normal. I get that too. What I'm talking about is a pronounced knocking sound (like someone hitting the block with a hammer) from just off-idle to around 1200 RPM, hot engine, light throttle. I think this is what JRG and Jumbo are also referring to.