Well, we got the starter figured out. Here is my next issue. Cold starts... Some days, it fires right up, others I have to stay in the starter and carry the motor over for several seconds while it blows white and black smoke trying to light. It acts just like it would if you opened the injection system and having to re prime. Once it is lit, it might stumble a few times and blow white smoke for a little bit, then settle out and be fine.

truck MUST have glow time to even think of starting. injectors are rebuilt, LP is hard wired with the key so no OPS crap on that. It pumps up while the glows are on. Several times, including yesterday, when it is cool outside, the glows only stay in for like a second. I know that is not right so I cycle the key again. Sometimes yes, sometimes no. I have tried unplugging the CTS on the coolant neck on the front of the motor and last year it actually worked so I though I just needed a sensor. I tried this yesterday and glow time was still 1 sec. I plugged it back in and got a full 10 sec of glow.

Usually, if I am going to have a bad start, the truck will idle much lower rpms, like it would have when warm. Some days it idles up and is obvious the pump is advancing correctly and idle is higher. Motor has more rattle and noise like it should.

So I am really scratching my head on the starting. I have a few codes pointing to the glow controller but that would have nothing to do with the pump advance and idle. They all seem linked at this point. All glows are Delco and visually and meter tested when I did the injectors. Truck runs good otherwise.

Is this too common of a problem to reply to?

I just read another similar post and suspect is glows. My plan for tonight was to just plug the truck in over night and see what it does in the morning. My problem is only present when the truck is dead cold. I know the truck is using water and oil but doubt that is the starting issue. My nose is also rather sensitive to burn anti freeze and I have not detected that but it sure as hell stinky like raw diesel on start up!

Is the plug in trick a good way to isolate the glows from an injector issue? Now if I have 1-2 bad ones, I am NOT wanting to replace all of them because my luck, I will break one in the block and this truck is going to be driven into the ground. With 300K, a slight knock, etc, I could care less about doing it right. band aids this this pig right now.

You said it yourself, the GP controller.

What is the pressure of the LP when hardwired?

No idea on LP pressure but truck will run all day with the T valve opened up. I filled a coffee can one time. I have the truck plugged in so I guess we will see what it does on the morning.


I realize something is not right when it glows for only a second but I will not try to start it like that. I will key it a few times until I get a good 10sec burn but that does not fix the problem. I am really wondering about automatic pump advance for a cold motor. Way different sound when it is right.

Do you get any DTCs?

I'd have to say the GP controller is your problem, it is common issue. The GP light is powered while GP controller is poweing GPs. And the PCM tells the GP controller when to start and stop glow, but if GP controller is bad then it might just cut out.

I think you should get a DTC29 if this happens though, so there could be a PCM issue, with it or some inputs. You'll know if the PCM is commanding it that way if you monitor voltage on pin B of the GP controller, which has a yellow wire coming from PCM to trigger the controller. It should be 12V when you turn IGN to ON until GP light goes out. If the two coincide then its your PCM not doing something right. The GP contoller harness must be plugged in for the GP light and PCM to operate correctly, so you'll just have to probe through the yellow wire insullation.

UPDATE: I plugged the truck in all night. Morning temp was about 45*F. Truck did not start clean. Still white smoke on start up and had to stay in the starter for 2-3 sec passed when it started blowing smoke to get it to light. I got 10sec of glow time. I can tell the GP controller is kicking in because the interior lights dim just a hair and you can hear the relay kick in and out.


I realize there might be a problem with the GP controller but it is not causing all my problems on startup. I am not sure if I just got rid of the suspected glow plugs or what.


One thing I will throw out is this truck is QUIET and smooth when it is warm. very mellow sounding and not like other 6.5s I have heard. Makes me wonder if I have a pump timing issue. Is this always adjusted on the pump or the optical sensor? Truck seems to run good when warm. Once it quits smoking in the morning which is about 5sec, I will take off and it does not smoke after that unless I pedal it hard.

How old is your GP controller? IIRC, there is a picture by TurbineDoc here about the GP sounds clicking but the contact was burned. So it does not make a good contact.

The GP function was verified by testing current draw on the batteries when I was trouble shooting the starter. GP controller in check. Now, why sometimes the ECU does not send enough glow time to that contactor, I have no idea but even when it does glow up correctly, the truck still starts like crap.

IIRC, the CTS tells them the temp. So CTS may be bad? sensing the wrong temp.

The expert can verify that or you can search about CTS.

change the temp sensor, it,s telling the glow plugs that its already warm,. hence the 1 sec glow plug time,. and i,d suspect your down a couple of glow plugs to make the problem worse,.

Nick
jmho

CIIR but by unplugging the CTS should tell the ECU that it is super cold out thus giving the max about of advance and glow time? That did not work the other day when I tried it but has in the passed. It may have already had a temp saved into the ECU too. Not sure there.


Also, how else do you test glows other than checking resistance on them and making sure they glow red hot? Both were verified a few months ago. I guess I could go check resistance again.

I will have to try the temp sensor trick again. I was certain last time I used the truck, that fixed the starting issue and I just needed a temp sensor.

change the temp sensor and the glow plug controller. Also If the engine is actually losing prime maybe there is a hole in the fuel lines somewhere .

Does anyone have a thermistor performance chart for the temp sensor to compare resistance to temperature?

I went out and fired the truck with the CTS unplugged again and it did do much better, less smoke, and higher idle. However, when I killed it and just restarted it, it went back down to low idle and there was no change in idle when I plugged the CTS in. Not sure if the ECU decided to disregard the CTS on the second start or what.

yes when you turn the truck off and restart it, it wont go back into cold start mode.

Per some data points I found in the FAQ, the CTS is good to go. I measured 2.4K ohms at 78*F. That seems in line. I will have to take a look when cold outside but I doubt it will be much different. Hmm. Kinda pointing me back to that pump timing.

If you need any more thermistor values they are in the GM manual I have. If you get the truck warm, it should be about 300 ohms in the 180*F area.

I will certainly take a looksy in just a few. Headed home from the shop about now.

I got 215ohms at 175*F. I am not sure if the response is linear or not or if there is a graph to show performance of these sensors. This seems a little off but maybe not enough to matter. Not sure yet.

Input?

Thats a little off, and not linear. 215ohms would be about 200*F, so its possible that the guage in the truck is a little low. I've checked with an infared temp reader and my water is a little hotter than the guage reads, and the PCM usually registers more temp than the guage. I think your CTS is good.

I tested with an external K type thermocouple on a few brass fittings by the CTS. I got 172* but that water will certainly be hotter. I just ran it on a 15 min rodie so I think water temp accuracy might be a hair lacking here. Now if the GMTD software I have ready that sensor, it should be fine as I monitored that when testing before. Seemed in line with normal operations. If not, if could be suspect. I am leaning towards good at this point though.