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Glow Plug Controller Function

doober

doober

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Location
River Falls, wisconsin
What causes the glow plug controller to turn on and off? Is it the CTS? Or the ECM? Or what? On my 95 I have experienced white smoke at start up. It has been around 0 degrees F. I noticed that when the glow plug light goes off in the dash it doesn't come back on like my other trucks do. The other trucks light cycles acouple of times before going out for good. I am going to go out and unplug the CTS and see if that takes care of the smokey white start. I will also see if the light cycles a time or two.

When it's cold out I like the light to cycle back on because if some of the glows don't take hold on the first 10 second duration after it starts the second light comes on the engine usually runs smooth.
 
CTS I believe is what controls the glow plug time. Depending on years through the PCM that then signals the glow plug relay and earlier years could go to relay directly ???

Keep in mind the forum is world wide so River falls is a lot colder than a lot get so give us some more reference temps you are talking about when it smokes and doesn't. 0F is dang cold to me does it start fine at 32F. Do you plug it in? If glow plugs are old they may be the problem. You can ohm test individually about 1 ohm each. But still quality of heat degrades over time. I would start there first. My relay is on its 3rd set of plugs. But you know more about your truck and the GP controller can go bad too. Its just more probable its the glow plugs themselves, cranking speed, old age, and dang cold.
 
Might be in stickies the resistance values vs temp for the CTS. If the timing is advancing I would guess glow plugs if timing not advancing might be CTS. If its just not after glowing then maybe the gp relay??? And or glow plugs themselves. My afterglow is really short more or less a blink on the dash light maybe 3 or so after glow cycles when its really cold. I think its 1-2 secs on 3 seconds off or something like that but yeah I can feel it smooth out the engine when cold.
 
95 6.5 diesel pickup. Okay guys thanks for your help. below 32f is when it starts to blow the white smoke at initial start up of the day. Truck can then sit for 4 hours or so and starts without smoking. Truck showed no syptoms of this during the summer months. I have only owened it for a few months so I don't know how it acted last winter.

Previous owner said when I purchased it that new heads and glows were put in last fall. I found a receipt in the glove box for 60g glows and two new batterys. It actually starts at the touch of the key but just has alot of white smoke for about 15 seconds.

I try to plug in overnight if the temp is going to get below 10f. I am thinking it is either the CTS or controller, or pcm, ecm but am trying to figure out what one might be causing it. See the truck is not having any after glow like my other trucks have. I have bought all the items for the overide glow plug fix but would like to see if something else is causing this before installing that.
 
Mine smokes like that for the 1st few miles during cold weather & sometimes longer when it's near or below zero. I do plug mine in or try to when it's below 20 degF.

It's normal during extreme cold & until the temp on the exhaust heats up a bit, it's just moisture from the combustion.

As long as yr not using any coolent yr good...:thumbsup:

Off topic a tad is a good chip or PCM can provide a little extended GP time & a few short after glows that help during extreme cold. My multi program chip even provides me a high idle option, sweet for the cold morning here in the midwest. Not sure what year yr truck is, but if it's 94 or 95 I could hook you up with a guy that can get err done for ya.
 
I went out last evening and unplugged the cts sensor and the glow plugs lit up for about 8 seconds. I cranked the engine over and it seemed to start fine. It was dark out but the truck was backed up under the garage lights and I didn't see the white smoke. The after glows turned on twice also. So it might be the CTS that is bad being the after glows came on and I didn't see the white smoke.

I drove the truck around with the CTS unplugged and it did seem like the truck had more clatter. So I am thinking the timming was advanced with the CTS unplugged. After acouple of miles of driving the service engine light came on. I pullled over and shut it off and hooked the CTS back up. The light then didn't come back on in the dash.

I will start the truck Tomorrow morning with the CTS unplugged and see if there is any smoke. I will take note of the seconds that the glow plug light in the dash is illuminated.
 
iirc the PCM uses the CTS to set timing and know the engine is at appropriate temps too. It will code if not over 160F in so many minutes. Then at 170F it adjust time from cold advance. You probably had the under miniumum temp for stable operation error code. I had that one once when a thermostat hung open. If you unplug the CTS it sets max glow time so it might mask marginal glow plugs. Keep in mind Wellman glow plugs and others can degrade and wear out in a year the set I recieved did. I would recommend AC Delco and Bosch.

I would measure resistance of CTS when cold and at operating temps and see if it correlates to resistance table before condeming.
 
IIRC you have Carcode. Take a thermometer and lay it on the intake manifold and verify the temp it reads with CC before it starts. This is done after sitting all night
 
95 6.5 diesel pickup
Thanks for all the information you guys have given me. I will pull the plug on the CTS Tomorrow morning before the kid goes to work. If it doesn't smoke at start up it is more than likley the CTS that is causing the problem? The guy I bought this from just put in AC Delco 60G plugs. I will also check the seconds that the glow plug light stays on in the dash. Last night when I unplugged CTS the glow plug light only stayed on for 8 seconds. But mabey the engine was still somewhat warm. No smoke though when I did start it unplugged. After glows did work also two times.

AK I don't have carcode so I am trying to wing it. If I can get this lap top figured out I do have GMCD Scan tech or what ever it is.

Scheiker, I searched and can't find the table for the resistance table for the CTS. Do you happen to know where it is?

I think it is supposed to get down to around 10F tonight so Tomorrow morning should be a good test for unplugging the CTS. Hope to get at least 10 seconds of glow time. If not I am not sure what would be wrong because I think I should mabey be getting more glow time. But mabey CTS is messed up and will find out Tomorrow by unplugging. Next day if I still have smoke by unplugging CTS I will try jumping the glows at the controller for mabey 15 seconds and see what happens.
 
95 6.5 pickup
I unhooked the harness from the CTS and I got 12 seconds of glow time. It was about 10F outside this morning. It smoked quiet a bit though at start up for about 15 seconds then smoke was totally gone. I did get acouple of after glows and that didn't seem to help the smoke. I should probably check for air in the fuel at the ip and after the ip. Mabey it is getting air in around the shaft when it is in advance timing or something I don't know.

What I don't understand is when I unplug the CTS I thought the computer was supposed to think it was -40f out and I was supposed to get a long glow duration. Well last night by doing that I only got 8 seconds. This morning I got 12 seconds. So there might be something else regulating glow duration.

I could jump or bypass the glow plug controller to see if the controller has bad contacts I guess. It could be that the compression is low to being this truck has close to 300,000 miles on it. But it runs so good other than the smokey start. And it doesn't start the smokey start until the temp gets to around 20f.

Lift pump is working and I put in a new one a month ago. I will have to put the GMTD Scan on it I guess. As long as it isn't hurting the motor it isn't that big of a deal though. Bought the nice looking truck for 800 dollars so I can live with a few problems. Don't really know the history of it because the guy I bought from only owned it for a year. He bought it from a dealer so he didn't know the history before him.
 
Well I have wondered if the actual glow time was a combination of IAT and ECT factors???

Unplugging the CTS should set max glow time I would think also but then I have wondered about IAT too. Once when I was chasing a slow start I rigged up a long test lead(s) made from a long 2 wire lamp cord and alligator clips. Then I would sit in truck and watch actual glow plug voltage on front drivers side glow plug lead with my DMM. Mine turned out to be PCM but I had to rule out glow plugs and relay.

You think it might be just be normal old age and 60G's (which are suppose to be a little slower heating than 9G's etc but more robust and less likely to swell)???
 
Thanks for posting the chart, Jess... guys, your first stop for information should always be the 6.5 Technical Reference Library ...

It has the information you need, put there and verified by the members here. If something you are looking for ISN'T in the tech library, it probably NEEDS to be, so that is our collective cue to solve the problem at hand, write it up, and get it into the Library... something any of us Mods will help you with.

In this case, a fast perusal yields some interesting things:

======================================

CTS - Coolant Temperature Sensor - Here is a list of the OHM readings for the sensor at various temps.
Info from chrisK1500

Glow Plug Override - a way of jumping the OEM GP relay to get extended glow time...

Here is a quick 'how-to' on installing a manual glow plug override.
Info from chrisK1500

Because Variety and different viewpoints are always handy, Here is another version of installing a manual glow plug override.
Info from Hydrauk

Glow Plug - ECT mod for longer running; use with Bosch Duraterms, AC60g, or other self-regulating plug only. Look here.
Info from chrisK1500

You don't have to get a reprogrammed PCM to do the fast-idle thing ...

Fast Idle Switch Mod - On vehicles equipped with the Electronic DS-4 Injection pumps, hooking up a high-idle modification is a simple matter. This thread talks about the process for both OBD-I and OBD-II vehicles.
Info from mfgguru

This Forum is, without a single doubt, the best technical source for 6.5 owners on the 'net... we have the best information, the best technical expertise, and the best members.

It is my hope that you continue to not only take advantage of the accumulated wisdom, but to take the time to write and add to it.
 
95 6.5 pickup, 290,000 miles stock
Thanks guys for your help. Schiker, I am not sure if it is the old age of the truck or the 60G's that is the problem with the white smoke at start up. I will have to do more testing I guess.

Ak Diesel, Yes I unplugged the sensor at the coolant crossover. What's weird with that is one time I got a 8 second glow time after sitting for around 8 hours with it unplugged. Then the next morning I got about 12 seconds of glow time with it unplugged. I thought the computer was supposed to think the ambient temp was -40 or there abouts when it was unplugged so I am not sure why I got the different glow times.

Another strange thing to me anyway is usually when I get the after glows to come on I can feel the engine smooth out some but that isn't the case. I think I need to check for air in the system. I got some very good responses from everyone here for sure. But when it is above 32f I don't have any smoke at start. I wonder if some air in the system would only make it smoke at under 32f. I need to check voltage at the plugs and even though the 60g glows are less than 1 year old I should consider them good until checking them. I should probably also put new squirters in it and check the compression.

JFaire, Sorry I missed some of the information that I should have first searched for before bringing my problems out in the open but my brain hurts from searching, most nights I am searching hear and the other place for hours. Most of the time I just like to read so mabey it isn't always searching but I do miss some things I am supposed to do for sure. Just ask my wife. She will let you know that I mess up alot. Oh, thanks for the compliment on the truck.

The truck in the avitar is a 92 6.5 that I have. The one with the minor issues is the 95 6.5. I also love my 95 6.5 burb and my other 95 6.5 std cab truck I just picked up. I am using the search button most every day because I need to give alot of love to try to keep my 6.5's in tip top shape. Oh, I am searching on a other site also trying to keep my durabux, up in running condition, so I can take my 5th wheel along with my family camping all summer long. This site has been a great help. Thanks all.
 
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