I have been noting a ruff idle for say 15 - 30 secs. when starting truck in the morning. have had TSB... only have 2300 miles on truck.. it did not do this the first 1500 miles... I have used a few oz.'s of Lucas Top Cyn. in one or two tanks! any ideas.. it has not been that cold... not below 55.. and that has only been this week...

 

It sounds pretty normal. Under 60 F, the grid heater and fuel heater come on. That is about the time you notice changes in how the truck acts until warmed up.

 

well I guess the the intake manifold temp has not kicked in yet.. as my engine block heater "light" has NEVER shown that it is cycling.. and yes the light comes on at test time... I should be able to check the heater becasue the temp should be in the upper 40's at night sometime this week!

 

The grid heater light does not come on when it operates. You will notice a slight dimming of lights, volt meter may move and engine sound may change a little under additional load as grid heater comes on.

 

what - it does not come on!! How do you know it has cycled then??? I shall look at the manual... are you sure then why does the dash have the light if it does not come on??? not that I am throwing beer cans at you.. but I don't believe it..

*** edited note **

as per the book page #207 - the wait to start lamp (what I thought was the heater sign/lamp) stays on while the intake manifold heater is cycling!!! I only threw one beer can at you...

 

Believe him...the amber light only works on the first pre-start cycle, after start the heater continues to cycle, but as the engine is already running, the amber 'wait to start light' does not function.

 

as I added to my above post... the book states the wait to start lamp stays on while the intake manifold is cycling.. I am not talking about when I start my engine.. I am talking about when I get in the truck ..

That is just it.. I have not seen the lamp on even for the first pre start heat cycle... I can check in the AM.. it should be around 47 - 50 in the AM...

 

It should come on for every start, regardless of temp, at least mine does. When the engine is warm, or it is warm out it's not on very long, but it always comes on. Maybe the heaters aren't working, and thats why you have the initial rough idle.

 

steve - it does come on for engine check... maybe it has not been cold enough but I will check in AM... I can tell you what happens in the AM ok... I think it should stay on for some time in AM... if not then maybe something is wrong...

 

I'd kinda think you would get a cycle or two at mid 40's. Load up the electrics and turn the fan on high. If it's cycling the fan will change speed with the cycle.

 

This is my 3rd Cummins with grid heaters, and the "Wait to Start" light is only on during the pre-starrt warmup with ignition on if the temp is below 60 or so. If warmer than that, the light will only come on for check light function and go out.

After startup the light will not come on, but if cool enough the grid heaters will be cycling on and off for 180 seconds if stationery.

 

that is exactly my point/question.. I will check in the AM... as I have never had the truck in 40+ temps... I will let you know in AM.. In the high 50's it did not cycle... or put another way the light did not ********* STAY ************** on after check..