I am kinda new to the whole diesel thing so this may be a dumb question... Why exactly does it hurt an engine to run it hard when cold, and so important to warm up properly??? and what does it do to it?? because i just saw a thread on here saying its more detrimental to leave the truck idling for ten minutes than to cut it off and start up again... Thanks -A.Wall

 

If the combustion temps drop enough, all the Diesel isn't burnt and it starts sticking to the valves leading to broken parts.

If you have a device to keep the idle up over 1k, this keeps the temps up enough to prevent this.


phox

 

so if its a cold morning is it better to let it warm up, or to just go ahead and start driving??

 

Happy medium.

You don't want to idle too much, but you don't want to drive a cold engine.

I have the cold weather idle in my ECM, after startup on really cold mornings, it gradually brings the idle up to 1200ish which gets the heat going quicker.

You can have it programmed in by any Dodge Dealer who knows how, they'll most likely charge 1/2 hour shop time to do this.
Here's the TSB outlining the procedure:
http://dodgeram.info/tsb/2001/18-019-01.htm

Most people just start up, let idle a couple minutes, then take it easy for the first couple of miles, then drive normal.


phox

 

Well the SMarty has a cold weather high-idle feature. Alright because what i've been doing is lettin her idle about 4-5 minutes and then just driving easy till get up to temp. Thanks - I've just heard so many different opinions on this

 

After it gets warmed up, could running your egt's on up burn out that fuel tahts stuck to the valves?

 

I would stay with 5 min max on idling! I actually prefer 1 min, unless I'm sitting in it and can rev the engine to 1200 rpm. Than driving easily, like you say, till at least the T-Stat opens. For sake of argument... I might define 'driving easy' as 10 psi boost or less on a stock truck!
The real key, IMO, is to get the OIL up to operating temp... which, on a Cummins, takes a bit longer. When I had an oil temp gauge, it would take 10 miles at 60 mph on a 30* morning to get oil up to 190* (avg cruising temp). Took about half that long in the summer.

On your original question... the biggest danger to running a cold engine hard (with extra HP) is blowing the head gasket. Have seen it happen at just 40 psi boost on a cool engine!

RJ

 

Not sure on that one.
Cummins doesn't suggest doing that, but they don't say not to.
They just recommend upping the rpms during cold weather idle to prevent it.


phox