Why are diesels so noisy when cold? - Ford Powerstroke Diesel Forum
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Old 01-02-2008, 08:25 PM
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Why are diesels so noisy when cold?

I know this is probably a dumb question for all you guys that have had diesels for years, but this is my first winter with one.

I was just curious why they're so noisy and rough running when cold.

Should I go to a different grade oil? I just changed it with 15/40 2k ago, so I'd hate to waste 40 bucks worth of oil if I don't need to. It runs in the 20s most of the time where I live in the winter with occasional dips to single digits.
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Old 01-02-2008, 08:31 PM
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ur oil is fine its just the diesels! they run like that make sure to have additive in fuel and allow plenty of time for warm up!
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Old 01-02-2008, 08:36 PM
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diesels only really need two things to fire....

Fuel

and Heat.....

Compression produces the heat with air.....

Injectors provide the fuel....

Now cold air makes it tougher for the air to get warm enough to ignite the fuel...even with the glow plugs. Topp that off with the oil being extra thick since it is what makes the injectors push the fuel into the cylender.....the combined two things make them run a little "off" when they are cold....

Just provide a little extra warm up time and know the nature of the beast...its nothing to worry about!!!
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Old 01-02-2008, 08:37 PM
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Yeah, I did notice that it runs a LOT better when I plug the block heater in overnight. I'm visiting my dad in Houston now, and even here with the 30 degrees it is now, it's really noisy when I start it.

Does anyone know technically why they run noisy when cold? I'm just curious as to what process actually causes it internally.
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Old 01-02-2008, 08:39 PM
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everything just has more stress when its cold. its hard to move all the fluids around when they are thicker because of the cold. thats about the best i can sum it all up!
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Old 01-02-2008, 08:41 PM
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Quote:
Originally Posted by tech10002 View Post
Yeah, I did notice that it runs a LOT better when I plug the block heater in overnight. I'm visiting my dad in Houston now, and even here with the 30 degrees it is now, it's really noisy when I start it.

Does anyone know technically why they run noisy when cold? I'm just curious as to what process actually causes it internally.
the noise is the injectors. Its called injector "knock"....

What happens is when the injector is functioning...the oil pressure is magnified through a intensifier piston....

When that happens...thats the louder knock that 7.3's and 6.0's have over common rail motors like the d-maxes and newer cummins motors. That noise is greatly amplified when the oil and fuel are cold since the injector, fuel pump, oil pump, etc have to work a little harder to get everything there. The combination of it all produces that knock you hear...
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Old 01-02-2008, 08:44 PM
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dam mark u know ur business!! lol.. i think u should for what u do for a living
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Old 01-02-2008, 09:27 PM
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Quote:
Originally Posted by tech10002 View Post
I know this is probably a dumb question for all you guys that have had diesels for years, but this is my first winter with one.

I was just curious why they're so noisy and rough running when cold.

Should I go to a different grade oil? I just changed it with 15/40 2k ago, so I'd hate to waste 40 bucks worth of oil if I don't need to. It runs in the 20s most of the time where I live in the winter with occasional dips to single digits.
Cycle your glow plugs 2-3 times. It has been in the teens the past week or so here and plugging it in at night and cycling the glow plugs makes it fire right up without being too rough.
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Old 01-03-2008, 07:19 PM
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Quote:
Originally Posted by Marc View Post
the noise is the injectors. Its called injector "knock"....

What happens is when the injector is functioning...the oil pressure is magnified through a intensifier piston....

When that happens...thats the louder knock that 7.3's and 6.0's have over common rail motors like the d-maxes and newer cummins motors. That noise is greatly amplified when the oil and fuel are cold since the injector, fuel pump, oil pump, etc have to work a little harder to get everything there. The combination of it all produces that knock you hear...
So that's why I wake up the neighbors in the morning. LOL

So what is an intensifier piston? Are they called that because they take oil at less than 3000 PSI and inject fuel at up to 20k PSI?

I think I have a pretty good idea how this HEUI system works, but I don't really understand the concept of the intensifier piston. Here's my take... The low pressure engine oil pump provides pressure to pump oil to the HPOP reservoir. The HPOP then sends high pressure oil up to about 2700 PSI to runners in the heads that then lead to the injectors. That pressure is controlled by the IPR, which is electrically controlled by the ECU. Inside the injector, some kind of electromagnetic solenoid valve(Maybe a pilot operated pintle valve???)directs the high pressure oil to the top side of a piston in the injector which forces the fuel into the engine at much higher pressures. The fuel enters the bottom side of the piston through a separate low pressure fuel rail.

Am I even close to how these things work? I'm just guessing on most of this, as I can't find a good theory of operation writeup on the internet.

I'd really like to see a diagram of these injectors. I'm curious how the oil returns back to the engine after firing the injector and also how the valving works in the injector on both the engine and fuel side--like does it just use passages covered by the piston as it moves, like a 2 cycle engine...

Educate me.
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Old 01-04-2008, 03:28 PM
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The 6.0 is suppose to run 10w/30 heavy duty diesel oil. I run Rotella right now. If I plug my truck in, I have no starting issues even in below zero temps.
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