Am I hearing things???

[jtomasik]

I just came back from a 2000 mile round trip highway drive. The truck seems to run fine, but I think one of my injectors is hitting hard. There's a very slight knocking sound during that hit. It doesn't sound deep like a rod, and it doesn't sound lighter metallic like a lifter or rocker arm. I did notice that I can't hear it at highway speeds. I'm thinking that maybe my extended time in the cab at highway speeds gave me a different short term impression of my truck, and I'm not used to hearing it running and idling around town. Oh, the sound seems more pronounced when it's cold. No, it isn't a miss...more like a cylinder's hitting harder than others. Yes, I know how crazy this sounds.

The truck has 161,000 on it now. When do you guys replace injectors as a maintenance item? Ever?

[Clay Henry]

Originally Posted by jtomasik

When do you guys replace injectors as a maintenance item? Ever?

Nope, too expensive to just replace unless they have failed.
Probably what your hearing is a result of the new ULSD....this will make it sound louder at idle because of the poor lubrication of the fuel.
When mine is burning straight vegi oil, you almost can't hear it idle. I have stopped at a light before after coming off the highway and actually thought my truck died cause I couldn't not hear it...had to roll down the window and turn of the radio to hear it. Very good lubrication from the vegi oil takes ALL the knock out of mine.

[jtomasik]

For those power stroke diesel owners who use the standard diesel fuels, does your engine sound louder in the cold? Does it sound like one cylinder might be hitting harder than others?

[Clay Henry]

yes, mine does. I use diesel fuel on startups and it is louder when its cold.

[Marty]

It is louder when cold then it is when it's warm imo.

As for the "knock" it could be injector cackle. Speak with Shane "sea71" about it... he has it as well. It's apparently air in the fuel system and usually comes from the #8 injector I think...
I used to have a sound clip but I can't find it. If I find it I'll post it up so you can hear it and compare it to yours.



Ok here is what I found..>

want causes the sound
A convergence of poor design decisions that maximizes the deleterious effects of HEUI systems in general and entrained air in your fuel system in particular.

, and why is it louder when cold and other times?
The fluid viscosity of your fuel and oil is lower when cold. This affects the fuel spray pattern emitted by the injector, which in turn affects the entire combustion event. The oil viscosity is also one of the variables that affects injection timing, so the timing and the combustion event itself are both a little 'off.'

can you stop the sound or make it quieter?
Yes.

Mine is completely gone now that I've added the in-tank mods, an Airdog, a pressure-regulated recirculating return fuel system, the high-pressure oil rail crossover mod, and a standard injector in the #8 hole.

Dennis Schroeder at ITP in Phoenix can set you up with all of the parts necessary to kill your cackle.

On several occasions I have astounded my fellow 7.3 owners when I start it up - the difference in smoothness and noise is that stark.

The in-tank, Airdog, and HPX all chipped away at the flanks of the cackle problem, reducing its RPM range and its overall tendency.

The fuel system and LL8 replacement completely eliminated it. My PSD is a smooth as a straight six.

[jtomasik]

Maintain, yes, I'd like to hear that sound bite. Thanks for the rest of the info, too. And thanks to CHenry for his info.

[Diesel_Diagnostician]

You can go to all that work that's described in MAINTAINS post or you can install a new number 8 injector and reflash the PCM....always works as well...