In reading the various threads here. It seems one of the causes of injector knock is low fuel pressure. Are there any other reasons injector knock can occur? Running low oil levels etc.

After seeing the internals of a dis-assembled injector could a broken internal spring contribute to the knock or would a total failure occur?

Can dirty oil be also a factor? As the miles rack up between oil changes it can become abrasive so could that also attribute to not changing oil more frequently?

i guess in asking this question. Once an injector starts knocking is the only solution is to replace the injector or a internal piece?

Just trying to understand some of the causes and solutions to injector knock. Thanks for your input.

 

Necro bump!

I know this is old but I also would like to know what some of the causes and solutions are to injector / fuel knock. And how to troubleshoot the problem.

I'm hearing a knocking or loud tapping sound above the normal diesel clatter when doing a light cruise around 50-55 mph. If I let off the go pedal the noise goes away completely. When I get back on the go pedal it comes right back.

I might hear it at idle but it's definitely louder when I'm cruising. It's a pretty distinctive noise and it seems to get louder if I run a tune.

I run Diesel Kleen and ashless 2-stroke oil in the fuel tank but not all of the time but there's really no difference in the noise. And I've noticed it makes this sound whether I'm running Shell Rotella T6 5w40 or Shell T5 10w30 and even Archoil.

Just did a fuel filter and oil/filter change about 300 miles ago and still no change in the noise.

The oil level is half way between full and low.
My fuel pressure is about 60psi at cruise (blue spring).
FMP bounces between 47.0v-48.0v/FLP between 13.8v-14.1v.
And ICP is around 900-1200 I think but I'd have to double check that again.

When I fire it up after an overnight cold soak the injectors are beautifully quiet. But once the truck gets past about 160* EOT I can start to hear the tapping/knocking.

I do have AE but the freaking contribution test looks perfect. I'm not sure where to go from here.

 

Try to pinpoint where the knock is with a engine stethascope or other sound transmitting device. Does it sound metalic or just a thump? Above at the head or below the head.
At the valve cover and a metalic sound suspect valve train issues.
Below the head suspect premature combustion [fuel knock]

 

Ok cool. Thanks dannyboy950. It definitely doesn't sound metallic. And it's definitely not a low thumping sound. It's kind of hard to describe but it kind of sounds like you are lightly slapping two small pieces of 2x4 wood together. Kind of like a clack or tap.

The few times I've listened for the sound at idle, I seem to hear it better from the wheel wells than from the top of the engine. And if I'm driving it sounds like it's coming from the foot wells, through the firewall.

I've got Sunday off so I'll do a better job of pinpointing which side it's on and exactly where it sounds louder.

You know, I'd love to have some sort of electronic tool that lets you view the injector in action so you can see if you have a lazy one or not.

 

It's really hard to pinpoint it to an injector do to the fact that
they are under all that stuff. You could pull a valve cover and run
it and take a listen. But it's going to be messy and the FICM will
be a pain to deal with hanging out in mid air.

Just use a lot of care and don't let ANY THING INTO THE OIL DRAINS.

 

shultzaberger,
I know this was awhile ago, but what did you end up finding? I have a 2011 6.7 with 140k miles and am having very similar symptoms/noise and it sounds expensive. I'm having trouble diagnosing it so far so any help would be greatly appreciated.

 

This is the 6.0 forum. You should check into the 6.7 forum as they would be up to speed on that motors(engine?) quirks.

 

6.7 injectors have a very different design and issue. As my understanding, the fuel is pressured directly, not indirectly by oil. So it doesn't have similar source of issue, although symptom can be similar.

Most of 6.7 injectors problem from what I heard was due to water in fuel contamination, and sometimes, odd metal shavings went through all the way to the injectors from the pump.

Maybe move to 6.7 forum for better support.