choke/idle adjust/whatever it is...

northvanmatt · Post by **northvanmatt** » Fri Mar 16, 2007 8:14 pm

hey hey all I don't know all that much about diesel engines yet but I drive a fire truck when I am not in my delica. the knob from what I gather is a bit of a high idle switch. Yes it also doubles as a way to warm up your engine on those cold mornings but diesels idle very low (Before you crank up the idle you should always let the motor idle normally for a bit before rising the rpm's) if you are going to leave your engine at an idle for a long time you should keep the rpms above 1000. This is due to the way the engine idles, it preforms better above 1000 rpm. it circulates oils better and may burn less fuel than if you leave it at idle for long periods. It also helps the charging system preform better that at idle and helps prevent carbon build up.
that is my two cents. when ever we idle our trucks at work we must idle them over 1000 rpms. I talked to our chief mechanic and those were the reasons he gave for the high idle of diesel engines

argo · Post by **argo** » Fri Mar 16, 2007 9:33 pm

Matt speaks the truth. The worst thing you can do to any engine is to let it idle excessively. I've let mine idle for a few minutes and the rpm automatically increases temporarily, I'm guessing this is a function of the engine control module. Anyone else notice this?

Small diesels are prone to "coking" especially if they have an EGR. Best to avoid idling at any speed. Without a load on the engine the fuel will not burn completely, allowing deposits to accumulate.

When I start mine cold, I let it run for four or five seconds, then I very gently increase the idle maybe 200 rpm [untill it smooths out].

Most of our vehicles are automatics, and with a fluid coupling it's pretty hard to suddenly dump a severe load on the engine. Diesels like to work, so once you're warmed up, drive it like it's stolen.

Adrock · Post by **Adrock** » Fri Mar 16, 2007 10:00 pm

my engine might like to work, but what about the rest of it?

And what about just increasing the idle speed? Is the 4-5 seconds really important?

argo · Post by **argo** » Sat Mar 17, 2007 7:08 am

You don't want to set the idle before the engine is actually running . I wait 4-5 seconds just to be sure the oil pressure is up [see Tribology] and it's firing on all four.

As I mentioned, I increase the idle very gingerly.

And no, I'm not a Ginger