Anyone ever wire in a cold advance / high idle manual disable / bypass?

Chaski

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I hate driving around the neighborhood while the cold advance is on in the wee hours of the morning. I am thinking of wiring the cold advance / high idle to a double throw switch. Up would be manual on, center position would be disable and down would be normal, where it is controlled by the thermostat.

Anybody have any suggestions? I am up in the air if I am going to be able to control the cold advance separate from the high idle.
 

cucvrus

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You can lube the shaft and screw the idle down so it does not race the engine so fast. I am assuming you are referring to the RPM's of the engine. Just adjust it down some and lube the shaft well.
 

jpg

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You can lube the shaft and screw the idle down so it does not race the engine so fast. I am assuming you are referring to the RPM's of the engine. Just adjust it down some and lube the shaft well.
Agreed. Keep a screwdriver in the truck and you can always adjust it back, if you need it as seasons change. I don't think this is something you need at your fingertips on the dashboard. If it were my truck, I'd rather lift the hood and turn a screw a couple times a year if it saves me from hacking up the electrical system and adding complexity to the dashboard.
 

Chaski

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I grasp how the high idle works, and really the only reason I'm thinking about fooling with the high idle is that it is tied into the same thermostat as the cold advance. The cold advance is what bugs me. I fire up the pickup on a 40 degree morning and it takes at least 10 minutes for it to get up to temp and kick off. There is no sneaking out of the neighborhood when the cold advance is active, it is LOUD. I really want to cut down on the morning cackle of the diesel. I can keep it simple with only three wires going from the thermostat into the cab with no hacking of the stock harness.
 

cucvrus

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Start it up put it in gear and go. Done don't take 10 minutes that way. I have mine off fast idle / advanced in 1/2 - 1 mile it is off and running normal on 0 degree days. Although I do like it at the intersection 1/4 mile away. I have 2 gas stations at the intersection when that light turns green and it is still advanced. I mash it a bit and it sounds like the engine is coming apart. I love the sound of a diesel on an icy cold morning. It sounds like a real machine.
 

dependable

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Part of the noise is the high idle, part is the timing advance.

Everyone has a different approach I guess, but I usually let it warm up and kick down before I hit the road. Seems a little easier on the rings.

You could un plug it a the two points by the IP. Your idea of looping it around to a switch in the cab would be pretty easy also, if it is an option you want. This would bypass system completely if you are in a hurry and worried about the noise.

Some warm up is probably good for the engine on really cold days, but then you should probably have a block heater anyway.
 
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Hasdrubal

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I have mine wired manually to an illuminated rocker switch. Did it because the system kicks down quickly, and there's a hill right by my house. The motor felt like it could use a little bit more on the cold advance, certainly goes better there, than with it kicked off. As soon as I'm up that hill, I shut it off. It's also nice to have sometimes when the motor has cooled down yet the stock system wouldn't engage at that temp.
 

cucvrus

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Just to let you know that advance is hard on the engine. Especially under load. That is making the detonation of the fuel happen when the crankshaft is still trying to push the cylinder up where the detonation is normally supposed to take place. I am not saying it will break something every time. And you may get away with it a long time. But it is still making that sound because the time of the fuel delivery has been changed and it is putting stress on the crankshaft rotation and every part in the lower engine. It has been 30 + years but I went to the GM school in Moorestown? NJ when these 6.2 engines came out and they were explained in depth. I still have the book. That was before the CUCV's were built because they were only talking about the upcoming build of the CUCV's and I was being schooled because of the Indiantown Gap base being so close by and we were the servicing dealer. So lets hear it. Am I right or wrong about the timing changing the firing time of the fuel. Is it taking place before the engine reaches the correct normal firing of the fuel? I am asking so if I am wrong I can be corrected.
 

TGP (IL)

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FYI
If it takes ten minutes to come off advance in 40 deg. temps, you have other problems.
0 deg possibly.

You can disable the circuit if you want.
The timing was advanced to help burn fuel and reduce smoke(emissions) until cylinder heat takes over.

You should always allow the advance to release before driving or loading the engine.
Sooner or later your going to be replacing the Crankshaft or piston.
Also you should always idle the engine a minute or two before shutdown to cool the cylinder temp. and,
Especially with a turbocharged engine to cool the turbo, and extend it's life.

Patience!
It's part of the learning curve of owning a Diesel powered vehicle or equipment.

This was the biggest problem GM had in the eighties along with oil change interval with the public not understanding the
Difference between a Gasoline powered vehicle and Diesel powered.
My 02
Tom
 

dependable

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Just to let you know that advance is hard on the engine. Especially under load. Am I right or wrong about the timing changing the firing time of the fuel. Is it taking place before the engine reaches the correct normal firing of the fuel? I am asking so if I am wrong I can be corrected.
That is correct, the timing is advanced for quicker and cleaner warm up of the engine. It sounds so loud because its is basically pre detonating, therefor should be load free until kick down, unless you are late for work or something.

If you live on a side street, or down a dirt road, it probably wont hurt to idle out in gear at low speed until kick down, but bringing it up to full RPMs in warm up mode can not be good for the long term life of the motor. You can tell that by the sound. I have been running 6.2s for decades, even before CUCVs were available, and still have 8 in my fleet. They are good motors, but they have their limitations.

I agree with TGP, a ten minuet warm up time probably indicates faulty thermostat or kick down sensor.
 

Chaski

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So, we all agree that mashing the throttle while the cold advance is on isn't a desirable thing to do. I think TGP and Dependable have the emissions concept backwards. Retarded timing reduces NOX emissions. GM probably bought the cold advance option on the pump so that they could offer a more conservative (retarded) timing at operating temperature, yet have it advanced enough when cold so that it would start easily. Yes, retarded timing also increases soot, but at no load (idle) there should be no soot anyway. I think GM was more concerned with NOX, that would explain why all the lighter 6.2 applications had the EGR system, to further reduce NOX emissions. Just my .02, and I wanted to toss it out there since it conflicts with what was written.

I think I am going to get a double pole three position make it so that I have an OEM configuration position where everything is as designed, a cold advance disable position, and a manual high idle position.

Also, next time I drain the coolant I am going to replace the thermostat for the high idle / cold advance.



UPDATE... I found some explanation of what the HPCA solenoid does in the GM 6.2 diesel engine manual...

"Purpose: 1) Emission control device. 2) Better cold starts. 3) Improves idle, reduces white smoke and noise when cold"

I am going to dig around in the Stanadyne book when I can find it.
 
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TGP (IL)

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" I think TGP and Dependable have the emissions concept backwards. Retarded timing reduces NOX emissions. "

Just to clarify for you The cold start system advances engine timing approx.. 3deg for a slower cleaner burn when cold controlling white smoke.
I doubt it would "knock" much at all if it were retarded.
Do read your Stanadyne manual.
TGP
 

sandcobra164

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It doesn't get very cold in SW GA but on a 17 degree day, my truck fires off fine and drops from high idle within 2 or 3 minutes of startup. On a 90 degree day, it drops within 30 seconds and regardless of the outside temperature, it never goes to high idle unless it's been parked for 12 hours or so.
 

llong66

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I had the fast idle/cold advance "switch" go bad on my M1008 go bad, with the price a new unit ~$200 as far s I could find) I bough a hummer hand operated fast idle switch, if doesn't advance the timing, but I can set the idle up and let it run up for a few. its also nice when jumping another vehicle, running my inverter and once I get my winch installed it will be nice. It takes a small amount of fabbing, but it works great. You can find them on various auction sites for ~$50. I did a write up with pics on the install if you are interested. Please feel free to ask if you have any questions!
 
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