92 slow idle when cold

[ipavlovich]

Just wondering if I should play with the idle adjustment because when starting from cold if temps are below 25F the engine doesn't idle at correct speed. I have to hold my foot on the pedal a bit until it warms up. Seems to idle just perfect though if temps are above 30F.

The other problem is that the truck smokes a lot when cold. Not just at start up but for at least 5 minutes after. There again I notice it more when temps are cold.

Also what weight oil is everyone using for winter? I don't use my truck very much in the winter but when I do it seems very stiff with the Delvac 1300 15w-40 oil. Any suggestions are greatly appreciated.

 

[nascar mark]

Hi and welcome aboard.



Sounds normal to me. Cold weather makes our engines run like that and other than pluging in can't be changed. I'm running Delvac 5/40 synthetic which helps.

 

[BushWakr - RIP]

If you're idle is normal while warm, and low when cold, it is usually due to the electrical draw caused by the intake manifold heaters.

When it's cold do you notice that your alternator gauge dips way down for a while then slowly recovers, then dips/recovers for the first while??

If so, then you have normal manifold heater cycling. If not, then you should start checking your connections, and your manifold temp sensor.

Usually at temps below 59*F the 'wait to start light' will stay on for about 5 seconds while the intake hearters activate. Then the light goes out, and you start up. The colder it is, the longer the light is on and the longer the cycling continues.



Your smoke issue is partly related.

First, the heaters help reduce smoke by warming the incoming air before it enters the cylinders. Cold temps/engine block cause smoke, usually blue, bluish/white, or white.

That is fairly normal.

When cold there is another system that helps reduce your smoke for the first while, it is the KSB solenoid. It's attached to the front lower middle part of the pump and has a single wire lead attached to it.

This solenoid increases the internal pump pressure from 4 bar to 8 bar which effectively increases the pump timing. Increase timing reduces smoke emissions. The KSB activates for a while during cold starts to help improve idle and reduce smoke, it then shuts off when the truck starts to warm.

So, observe your alternator gauge and watch for the cycling I mentioned and let us know how that works. We can diagnose or eliminate the intake heaters/sensor from there.

Second check your KSB solenoid and second temp sensor for function. When the truck is cold, remove the wire from the KSB, turn on the key (don't start it) and hook up a dc Voltmeter to the wire (+) you should have 12 (or 10) volts. If you have voltage you know the temp sensor for the KSB is working.

Start the truck and let it idle for a minute, then remove the KSB wire. Do you see/hear a difference? Listen closely as some are only slightly different. If it is working it should make a change to the idle speed, sound, quality, and reduce smoke a bit.

If you detect no change then further snooping into the KSB is needed, but it may not be working right.



Ok this is kinda long so I'll finish up by suggesting you look in "readers rigs" gallery. In there you will find pics that show the pump, and its main parts including the KSB location. For the sensor that runs it, just follow it's wire back to the sensor on the intake manifold near the firewall.

Here's the link:

https://www.turbodieselregister.com/user_gallery/displayalbum.php?&albumid=453



Hope that helps.



Bob.

 

[formula]

Note on the KSB wiring:

My KSB temp sensor fried (nice stinky cloud of smoke from under hood) a few months ago. I was able to get a new sensor from the stealer for about $50, I think it was called a "thermal switch", not to be confused with the grid heater sensor. However, stealer had no idea about the little wiring harness that connects from the shutoff solenoid/temp sensor/KSB. If you need one, the cummins part # for the harness is 3923303 (about $16). The KSB will make quite a difference in the cold idle and cold idle smoke. Also, it's just the nature of the beast to run a little rough and smoke a bit when it's stone cold. Just get in and drive, not the best thing to let it sit and idle waiting for it to warm up (it won't).



Sean

 

[rowland]

Cold Oil

I winter over in Fairbanks Alaska and it does tend to get a little cold at times. I run either 0W-30 or 5W-30 synthetic Delo 400 at this time of year. Oil makes a big difference in cold weather starts, with the 0W-30 I have managed to cold start (no heaters) to -25*F. It was not a happy truck.



Normally I plug in, however even with 4 heaters it will run rough for a little while at below zero temps.



I also up the idle in the winter months just to compensate. Some people here also install manual throttles to help with warm up.



Like mark said, sounds fairly normal to me.



Isaac.

 

[formula]

How's about an Espar heater for your engine?

Speaking of... ... . does anyone in here have an Espar? I've been seriously thinking about getting one. (perhaps a new thread is in order)



Sean

 

[ipavlovich]

Thanks everyone for the information! The manifold heater is cycling properly as indicated by the amp meter and lights dimming.

Has lots of blue smoke alright. I will check the KSB solinoid for sure and let you know if that's it. Sure sounds like the problem.

This is such a great resource! Thanks again.

 

[ipavlovich]

no voltage at KSB

Well I checked the Voltage to KSB soliniod and there is nothing. I aslo started the truck and pulled the wire off and couldn't detect any change. I'll be checking the sensor that runs the KSB next.

Thanks again.

 

[BushWakr - RIP]

Sounds like that may be the problem... the temp sensor for the KSb fails more often than the KSB itself.

It may even be a bad connection, so check, clean and retry before spending any $$$.

You may also consider having your pump timing adjusted a bit too, that will also help,, assuming you haven't done that already.



bob.