Turbo related warm start issue on 6.5TD -94??

[Bushido]

Hi all!

The name's Anton, I'm from Sweden and new to these forums! Pleased to make your acquaintance!

I would like to start off by asking a question, if I may. Thing is, my 1994 chevy silverado 6.5TD 4x4 has been suffering from a "Won't-start-while-warm"-issue for quite some time. Whenever the engine has gotten up to working temp, the car is extremely hard to restart if you shut it down. You either have to wait for the engine to cool down (either by leaving it alone, or by dumping a gallon of cold water on it), or you can sometimes force it to start by simply running it on the starter motor, turning it over for quite some time before it eventually awakens... I've been trying to troubleshoot this issue for a while now, and most of the people I've spoken to suggested that it was probably the injection pump that was starting to wear out... And it seemed to be the logical explanation, and so I let my truck sit while trying to save up cash for the pump replacement or rebuild (both of which are very costly were I live, we're talking up towards 2-3000 usd...). I'm a university student with no job, so money isn't exactly plentyfull... Anyhow, the car has also been suffering from a rusty turbo pressure pipe (the one linking the left side exhausts to the turbo) with lots of holes in it, and so the turbo hasn't really had any mentionable boost at all. The car has run allright however, so I haven't bothered getting the pipe replaced. Today however, for lack of something better to do, I thought I'd see what kind of difference a solid pipe would do. I welded up an improvised piece of piping (not pretty, but functional) and mounted it to my truck, and I was delighted to find that the truck ran so much better and even had a nice little turbo whistle going! I took the car out for a testrun, and it ran really well! Upon returning home I thought I would just try and restart it again, just for the hell of it. Before, you could count on the engine not starting if you had been out driving for more than a couple of minutes. and this had been a half hour test drive. Anyhow, I was extremely suprised to find that the car started! I thought it was just a fluke, shut it down once more, left it sitting for a minute or two and tried again. Once more, the engine roared into life! I was shocked! I mean, I had been out driving for well over half an hour, and up until now the car has almost always gotten cranky from anything longer than five minutes. Drive more than that, and you could count on it not starting again once shut down. But not so this time...

I took the car back out on the road and drove for another hour, stopping and restarting it every now and then. It started without fault every time, no matter if I tried starting it immediately upon shutoff or after waiting for several minutes. Something has obviously worked wonders, but I can't understand what it is. Somehow mending the turbo pressure pipe has rid my truck of a fault which everyone thought was probably a worn out injection pump.

Now, Is there anyone out there who can shed some light over this mystery?? Is there any way a turbo lacking pressure could affect a car this badly?? Or is there any way a fully pressurized turbo could work magic like this?? I'm really shocked, I never thought a turbo issue could be related to a warm start issue... If anyone knows anything about what's going on, I would really appreciate it if you would help me shed some light on this mystery. If you need any further information or something just let me know and I will provide whatever you need! I just need to know if I can trust the car to start while warm everytime from now on , or if this is something else entirely and I should expect it to start acting up soon again... If anyone has heard of anyhting like this happening before, please let me know!

I had this one theory that maybe the turbo has been restricting the airflow rather than helping it while the turbo was not operating at full pressure, and so the truck has run on an extremely rich mixture resulting in flooding of the engine and an off diesel/air mixture. Thus there would be uncombusted diesel left in the cylinders from the previous run which might act as a sort of reversed choke (instead of rectricting airflow you up the diesel), and choking a warm engine usually doesn't work... This could explain why the truck wouldn't start warm before, and now that the turbo operates at full pressure the fuel mixture is much better and the car starts even when warm. Does this sound reasonable at all?? I'm not looking for a complete diagnostics of what is or has been wrong with my car, I'm just worried that the two issues really are completely unrelated and the car starting when warm is just a coincidence and has nothing to do with the turbo now working. I don't really feel like I can trust my truck before I know if I've actually solved the problem you know... If anyone has any input to share I'd much appreciate it

Sorry if this has been asked already, I tried seacrhing but couldn't find any relevant results... And I sure never heard of a turbo mending a warm start issue before...

Thanks in advance!

Oh, and sorry if you're having a hard time understanding or following what I'm talmking about. English is not my first language, and so I sometimes struggle for words and phrasing fit to describe what I actually mean... if something needs clarification, just let me know and I'll try and rephrase myself. Here's a very brief summary of what I wanted to say:

I have a turbo diesel truck that had a turbocharger that wasn't getting the proper amount of propulsion from the exhaust because of a rusty exhaust pipe. At the same time my truck was also having difficulty starting when it was warm (which was thought to be an injection pump related issue). Now that I've replaced the rusted pipe and allowed the turbocharger to function properly again the issue with the failure to start when the engine is warm has gone away too. Question is, why? Could the two really be related, or is it just a lucky fluke and I still need to troubleshoot the warm starting issue?

Regards,
Anton.

 

[ak diesel driver]

try pouring water on the Injection pump next time and see if it starts better. if it does it's time for a new one

 

[Cumminsfever]

My theory: The engine is correctly burning all the fuel being put into it, and is running cooler.

My guess would be the pmd and/or pump going bad.

 

[Bushido]

try pouring water on the Injection pump next time and see if it starts better. if it does it's time for a new one

Thanks for the tip! It helps sometimes, but not all the time... I usually try to pour water right on top ot the injection pump, but it doesn't work every time. So I'm not certain if it's the pump being cooled down by the water or something else entirely when it does in fact help... Seems a bit inconsistent to me you know...

 

[Bushido]

My theory: The engine is correctly burning all the fuel being put into it, and is running cooler.

My guess would be the pmd and/or pump going bad.

Hi man, thanks for the info! So it does seem reasonable that the turbo now working might have helped with the warm starting issue?

I understand... That probably means the pump is still going bad seeing as the PMD has been relocated to a cooler place in the engine bay... I had been hoping for it not to be the pump as that is an insanely expensive job over here, but perhaps it still needs to be done... I'll try and test it out further and see what I can come up to, thanks!

 

[handcannon]

Do you have any mechanical experience? Tools available?

If so you could save a fair chunk of money by doing the IP swap yourself. I'm like you, very limited income. I've never done anything like this yet, but with the help from the guys and gal on here I won't hesitate to do the job.

Don

 

[Bushido]

Do you have any mechanical experience? Tools available?

If so you could save a fair chunk of money by doing the IP swap yourself. I'm like you, very limited income. I've never done anything like this yet, but with the help from the guys and gal on here I won't hesitate to do the job.

Don

Well... A little bit... I'm not completely unskilled to put it like that. I do most jobs on my own vehicles, services and so on, and I do construct various things out of metal. Have dona rebuild (not from scratch and up though) on a couple of mopeds and motorcycles. But I've never even attepmted a job like this myself... Isn't it supposed to be insanely difficult? Don't you need any kind of specialist tools? I've heard that you need to get the pump timing exactly right and I'm really worried I might mess it up... But you really think I could try it myself?


I went out for another test drive just now, cold start went much easier than yesterday now that the batteries are properly charged but the warm starting issue seems to have worsened yet again... It's not as bad as it was before, she still starts. But you have to run her on the starter motor for a little while before she jumps into life... Seemed like it helped to give her a small push on the accelerator to get her going, could that be an indication of something?

 

[flmike]

just a thought now that turbo is up to speed ie the crossover pipe fixed i would imagine the egt's are way down causing a lower under hood temp when you dont have proper boost the egts go through the roof.. as for not starting hot next time pour cold water on the pmd where ever you relocated it to i know its new but solid state devices and heat dont get along to well..

 

[Bushido]

just a thought now that turbo is up to speed ie the crossover pipe fixed i would imagine the egt's are way down causing a lower under hood temp when you dont have proper boost the egts go through the roof.. as for not starting hot next time pour cold water on the pmd where ever you relocated it to i know its new but solid state devices and heat dont get along to well..

Thanks for the tip! I always assumed it couldn't be the PMD causing the issue since it was a consistent "Woin't start while warm"-problem and seeing as how the PMD had been recently relocated, but as you say there's no harm in trying it out! I'm gonna see if I can't device a simple test, trying to cool different components (PMD, IP and starter) separately and see which ones affect the starter issue!

 

[MihaiPirvu]

Anton, is appear that you are withholding some info here, posted @ dieselplace.....QUOTE : " You see, when the engine is warm and won't start, it sounds like the starter motor is spinning faster than it does normally... don't know how to describe it, but it's a sort of sped up knocking sound... You can tell very clearly from the sound if it's going to start or not, and it sounds faster than it does when the engine is cold and will start normally... ". In order for this community to help you, you have to give us ALL the dates you know about the problem. So, let me drop my 2 cents here..Your starter is history, have a broken or cracked head or worn out head bushing or is loose. Also you may have a bad "crown" and if is not yet bad, will be shortly. That "speed up knocking sound" said all, the starter does not engage the crown and the knocking is destroying the crown and starter dentures. how was posted @ dieselplace, you NEED about 400 RPM to start this engine and if the starter's head is damaged in any way or the bushing is worn out, the starter will have a radial play and when you try to start it will kick the crown. When is not kicking the crown and it is engaging it will have a much lower RPM. If you try to start from the ignition key and it doesn't do nothing but a little "click", then that smaller cylinder from starter is bad as well, as it have some electrical connection inside. This connection get bad usually when the batteries are week and we keep trying to start ( make a flame and burn the contacts). Anyway, you will have to change that starter. Another thing will be that your "Open conical air filter mounted directly on turbo inlet" it is not the right filter for this engine, especially one with "S" vin number which I believe that you have on your truck. I know that there the temperatures are not to high in the summer but, your engine is sucking air from the engine bay (hot air), and that air is a lot hotter AFTER you turn off the engine. Where maybe, during the winter and for short distances the engine may like that temperature, I am sure that during the summer is not so happy. however, how I said before, AFTER you turn off the engine, the air sucked will be a lot hotter and you can have that hard start because of it also. So, the best is to return it to factory design. And same with the PMD....if you have to have it in the engine bay, the cooler place after you turn off the engine will be....on the IP. Other way, out off the engine bay with it. Once again, my 2 cents.....

 

[Bushido]

Anton, is appear that you are withholding some info here, posted @ dieselplace.....QUOTE : " You see, when the engine is warm and won't start, it sounds like the starter motor is spinning faster than it does normally... don't know how to describe it, but it's a sort of sped up knocking sound... You can tell very clearly from the sound if it's going to start or not, and it sounds faster than it does when the engine is cold and will start normally... ". In order for this community to help you, you have to give us ALL the dates you know about the problem. So, let me drop my 2 cents here..Your starter is history, have a broken or cracked head or worn out head bushing or is loose. Also you may have a bad "crown" and if is not yet bad, will be shortly. That "speed up knocking sound" said all, the starter does not engage the crown and the knocking is destroying the crown and starter dentures. how was posted @ dieselplace, you NEED about 400 RPM to start this engine and if the starter's head is damaged in any way or the bushing is worn out, the starter will have a radial play and when you try to start it will kick the crown. When is not kicking the crown and it is engaging it will have a much lower RPM. If you try to start from the ignition key and it doesn't do nothing but a little "click", then that smaller cylinder from starter is bad as well, as it have some electrical connection inside. This connection get bad usually when the batteries are week and we keep trying to start ( make a flame and burn the contacts). Anyway, you will have to change that starter. Another thing will be that your "Open conical air filter mounted directly on turbo inlet" it is not the right filter for this engine, especially one with "S" vin number which I believe that you have on your truck. I know that there the temperatures are not to high in the summer but, your engine is sucking air from the engine bay (hot air), and that air is a lot hotter AFTER you turn off the engine. Where maybe, during the winter and for short distances the engine may like that temperature, I am sure that during the summer is not so happy. however, how I said before, AFTER you turn off the engine, the air sucked will be a lot hotter and you can have that hard start because of it also. So, the best is to return it to factory design. And same with the PMD....if you have to have it in the engine bay, the cooler place after you turn off the engine will be....on the IP. Other way, out off the engine bay with it. Once again, my 2 cents.....

I did not mean to withhold anything, no special reason for not posting it here other than the fact that I forgot to add that information.
Thanks very much for the info and the theory, but I don't think this is correct. Yes, the sound is different, sped up and knocking. But it is not the sound of gears skipping over each other and generally disintegrating. The starter engages properly and the engine definitely turns over. I know for a fact that the gears on the starter motor and the corresponding gear in the engine are in good nick as I had to remove the starter motor not so long ago in order to reattach the power lead which had come off. Inspected everything at that time, no worn gears as far as I could tell. The starter could very well be bad anyhow and needing replacement if it doesn't spin fast enough to start the engine, but I'm sure it engages properly and turns the engine over. The sound of gears skipping and wearing each other down without the engine turning over would in all likelyhood be pretty bad I think, I wouldn't have kept it running if it had made a strange sound like that.
Thanks for the input about the filter and PMD, I'll switch back to original filter box and move the PMD out of the engine compartment What is an S vin number by the way?

 

[MihaiPirvu]

The 8th digit at the Vin number. (Vehicle Identification Number). They are: "S" have a EGR (exhaust gas recirculation) or "F" (non EGR). 1500 should be "S" and 2500 and 3500 "F'

 

[Bushido]

The 8th digit at the Vin number. (Vehicle Identification Number). They are: "S" have a EGR (exhaust gas recirculation) or "F" (non EGR). 1500 should be "S" and 2500 and 3500 "F'

I see, thanks for clarifying!

 

[MihaiPirvu]

Sorry, I had to take a phone call and I didn't reply all from the first time... never cross my mind that you withhold info with any reason, just that in this site the information is not complete, maybe there was not the right term used by me "withhold" but, same as you, English is not my native language....sorry for that.

 

[Bushido]

Sorry, I had to take a phone call and I didn't reply all from the first time... never cross my mind that you withhold info with any reason, just that in this site the information is not complete, maybe there was not the right term used by me "withhold" but, same as you, English is not my native language....sorry for that.

No worries, it just never occured to me to write it because no one asked about it. It's hard to list everything that's wrong about your car without being asked the right question you know. At the dieselplace I was specifically asked about the speed of the starter motor in various situations, and so I answered said question. Didn't think to write about it there either before someone asked
Cheers

 

[NVW]

Google: ENGHMOTORS

Stefan used to be a site vendor, he has a bi-directional scan tool that is just for the 94-95 6.5 trucks, You can set your TDCOffset with it and read and clear codes. He also has other stuff for these trucks.

He is also from Sweden.

 

[Bushido]

Google: ENGHMOTORS

Stefan used to be a site vendor, he has a bi-directional scan tool that is just for the 94-95 6.5 trucks, You can set your TDCOffset with it and read and clear codes. He also has other stuff for these trucks.

He is also from Sweden.

Thanks for the tip! That program seems really neat... Would be great to be able to read problem codes etc. Thanks!