My understanding of the PCM function is that it already does this. 140 degree engine oil temperature and above (PCM doesn't pay any attention to coolant temperature) it won't run the GP's.

 

I agree with you on this and especially for ARCTIC_RAGTOP in the Northern Territory. Interesting thought on the chip tuners getting involved (could be another $50 tune for them). I am not going to change mine anytime soon though just going to observe for a while. I had a medical issue come up that won't allow me to drive for six months, hopefully that's all.

 

Correct, my truck stops energizing GP's at about 133 degrees EOT ...

 

If I forget to flip the switch off after the normal cycle of the glow plugs and if my motor (oil) is warm on the next start my GP will not run.

Arctic, mine is not set up control the time they are on. If my switch is on, the GP's run normal. If its off, they don't run at all.

Like Madpogue said, I try to flip the switch back on after the last run of the day so the next day they will run normal. I have forgotten to do this and it won't start the next day. If my wife takes the truck, I leave it on for obvious reasons, LOL.

 

With mine its the same IF you forget to off the switch no problems at all, the PCM makes his NORMAL work.

But again my question for madpogue and Hussler, is there any REAL problem in the GPs or engine IF you NEVER flip the switch ON?

 

If the engine is just warm enough to start, but no hotter, it'll be a little less efficient (and will pollute a bit more) without the added heat from the GPs. That's the reason the PCM keeps them on after start.

 

Ok, thank you, so I suppose that the GPs dont get damaged if they NEVER get on, right? They dont form any carbon or something like that if never ignit?

 

Hm, that I can't say for sure. But I can't imagine anyplace where it NEVER gets cold enough that you'd want to run the GPs at least once in a while.

 

Yes you are right, but mostly in my state I dont need them, so my concern is IF I dont get on them they damage in someway, my common sense tell me that they dont, but who knows. Curiosly when I get on them there are more white smoke in the first start. IDK.

 

I know this thread is several years old but I just installed a manual GPR bypass momentary contract switch and thought I'd add my two cents to the discussion. My switch is completely manual and the PCM is no longer in the circuit except to light up the Wait to Start light.

On cold mornings I use the same start procedure as my excavator, which has a manual glow plug switch. First I crank the engine over a couple of revolutions with no glow plugs on to get some fuel oil in the combustion chambers. Then, without cranking the starter, I hold the GPR switch on while the WTS light it is lit, or maybe a little longer, depending on how cold it is.

Then I crank the starter with the glow plugs off. I think this lets the starter crank a bit faster without having to feed the glow plugs at the same time, and the glow plugs are still very hot. If it's idling rough when it starts I hold the glow plug switch on for a few moments 'til it smooths out.

Seems to be working very well. It fired up immediately yesterday morning with no block heater at 17 F. I know that isn't very cold for some of you guys.

Bob

 

Interesting older thread. I like the comments about the GPs and GPR's operating cycle. Gives me something to think about for the next GPR replacement. I'm still running the OEM replacement, but have considered the Stancor as a replacement option. If (when) a replacement is needed, I'll have to decide if I want to include the switch, too.

 

I wanted to add to this.

A problem that I see happening with not having the glow plugs cycle is..

CARBON BUILDUP.

then when they fail, the carbon buildup will not allow the removal of the glow plug.

just something to think about

 

Yes, this is a valid concern. My thinking, or maybe wishful thinking, is that the combustion chamber runs hot enough when we're rolling down the highway to prevent and/or burn off carbon deposits. And, we can occasionally manually extend the "on" time to burn off any deposits.

There are a lot of guys running the manual GPR switch and, although it doesn't prove anything, I've yet to hear of an actual problem.

But yes, there probably is a certain amount of risk involved.

Bob

 

Not enough engine temp to burn off carbon. You need a functioning glow plug to get hot enough to burn it off

 

Bob does make a good point though. A lot of equipment and machines have this feature. Tractors, welders, light plants ect......