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6.5 is surging and bucking

Discussion in '1982-Present GM Diesel' started by 73k5blazer, Mar 23, 2007.

  1. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    So my '97 K2500 with 6.5 TD is starting to act up.
    The truck has just about 200,000mi on it. I bought it fairly young with only 13,000mi on it, the injection pump and PMD were replaced under warranty at about 45,000mi. It is manual transmission equipped.

    It's acting really weird now. It surges, like a power boost, then backs off quick, causing a buck. But it doesn't cut out. When the PMD went before, it was a defined cut-out. I've replaced my fuel filter quite regularly at around 10k intervals, the lift pump has gone out twice, I know what that feels like - The truck still runs and drives, but if you get on it, it cuts out. It's not that.

    This is new. The power boost surge then a quick back off. my truck is a manual transmission, so the back-off causes a buck and driveline shock. I suspect in an auto tranny, the torque converter would soak it up and you wouldn't feel the buck.

    '97 was the first year for drive by wire accelerator too. It has always had a problem with cruise control, trailers and hills. If I was using cruise control, with a trailer, if I get into hilly areas and forget to turn the cruise off, it will kick and buck going down hills, like GM didn't do enough testing with the drive by wire on the manual trans. It has always done that since new.
    That feeling is what it feels like now, only it's unloaded on flat roads.

    Oh and, it only does it when it's cold. It's not cold outside now, in the 50's and 60's, it mostly acts up just for the first 10-15 minutes while the engine warms up, then the problem subsides. I can still kinda a feel a surge when it's warm, but nothing like when it's cold.

    Any ideas where to start to diagnose this one? Drive by wire system? Injection pump? It's not popping any codes, I've a buddy with a tech 2, no codes.

    I can still drive the truck, but experience tels me, problems like this don't fix themselves and will most likely get worse pretty quickly.

    Thanks for any insight.
     
  2. imiceman44

    imiceman44 1 ton status

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    The way it's acting is like it's starving for fuel which surges then drops after it gets fuel.
    If I was a betting man I would say IP, but it could also be a leak in the fuel line where it sucks air from a crack and gets a bubble, then when that passes it's fine again.
    But my bet goes to IP, it might be wearing out and not getting enough thru, and your problems with it loaded and uphill might not have been the drive by wire but an IP on it's way out.
    Let' hear more opinions and then if someone else concurs check the IP
     
  3. smalltruckbigcid

    smalltruckbigcid 1/2 ton status

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    I know this is going to sound dumb but change the fuel filter first. I just had similar symptoms from a 6.2 and it was all better with a new filter.
    George
     
  4. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Well, I did change the filter for fun, same deal.

    The thing with it in cruise loaded going thru hills, it always did that, even when it had 15,000mi and even after they replaced the IP under warranty in 1999 when the truck had 45,000mi on it.

    Are there any tests for the PMD?
     
  5. azblazor

    azblazor 1/2 ton status Premium Member

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    Have you scanned it for codes?

    Most guys with the electronic 6.5 diesel have a spare PMD to throw on for troubleshooting or sudden failure. I have 2 electronic 6.5s and I carry a spare FSD in each. You can pick them up used pretty cheap on ebay. Do you have yours remote mounted on a cooler?

    I think 93 was the last year for an actual throttle cable. Any electronic 6.5 uses a potentiometer for an accelerator.
     
  6. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Yeah, I checked with a Tech II for codes.There are none.

    I ran the diagnostic procedure as if I had a DTC 78, there were no problems. I have full vacuum when I should, the wastegate isn't sticky or anything, and the solenoid is operating as designed.

    So I ordered a used PMD with a remote harness and heatsink, and I'll give that a try. It's a good upgrade to have the remote heatsink kit anyway, and a good idea to have a spare PMD, so I figure it won't hurt me to have that stuff.

    If that isn't it, I really don't know where to go.
     
  7. azblazor

    azblazor 1/2 ton status Premium Member

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    If the PMD/FSD doesn't do it then remove and clean all ground strap connection points and even ohm them out, especially in the engine bay. Poor grounds may cause subtle problems with drivability due to signal loss to the computer.
     
  8. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    I bought a used PMD, heatsink, extesion harness and new #5 resistor.

    It barely idles. I have a feeling my new used PMD is bad.

    Is it possible it was using another number resistor and the #5 I bought is causing the problem. It's dark out now, so I can't see, I'll try and stick a mirror down in there tommorow to see which one my PMD has on it. I was told 5 was factory and if you changed you needed to time the pump? Anyone have a procedure for that?
     
  9. azblazor

    azblazor 1/2 ton status Premium Member

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    If you have access to a TECH II there is a procedure here: http://www.thedieselpage.com/archive.htm - if you are not a member it is worth way more than the 20-25 membership fee.

    You could very well have a bad PMD if you bought a used one. Ask them for an expididted replacement.

    I looks like you have about 150K on your Inj pump and Injectors, which is about twice what the factory recommends for optimum performance.( I know....for what its worth).

    I don't think ( don't remember for sure) you have to re-time just because of the resistor. I'll post the TDCO relearn procedure below but I don't think that's your problem: (from a post on TheDieselPage)

    96-2000

    1st, you need a 'scanner' or tech 2 , something that will read the stored data
    in the pcm. (i.e. CarCode ( obd-2.com ) and a laptop).

    Your are looking for the TDCO value.

    2nd, do the
    Key on/key off routine to clear the current TDCO,
    * pedal to the metal,turn on ign(don't start eng ) wait 45sec in this state.
    Turn off ign, release pedal, and wait 30 seconds. TDCO should know be
    '0', check scan data to verify

    3rd, start engine, when the coolant temp reaches 170 degrees, PCM will
    set the timing. ( you will here the TDCO being set by engine noise changing)
    Check scanner for value), ( search posts for reccomended /TDCO values )

    If TDCO not within acceptable range, than with engine off, rotate pump
    1 mm at a time and repeat, step 1 - 3....
    (see posts for mechanical adjusting of inj pump
    procedure)
     
    Last edited: Apr 5, 2007
  10. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Yeah, that place *seems* nice, but I tried to become a member there back in Oct 2004 and received a nasty email after I registered for the forums saying that my membership was "denied" and that I wouldn't be allowed on the site.

    I guess they didn't want my money.

    When I first registered for the forums, I got a form email saying my membership was subject to being approived by forum administrators, then a couple days later they "denied" me. I never made 1 post.

    I've never been back there since. I don't know what the problem was, and frankly at the time, I didn't care, I had solved my issued that initially brought me to that place, and wasn't about to waste my time with people that outright denied me without asking any questions. I don't know who they thought I was, but they obviously mistook me for somebody else, and I didn't feel like wasting time with people that didn't take any time to evaluate a situation.

    Anyhow, still seems like there's some good info there, but, my id is blocked, so, alas, they apperently want to keep all their info under lock and key and not share it.

    The info you post, is, much appreciated, thanks! The place is sending me a new (used) PMD, should be here tommorow, if UPS works tommorow, I dunno.
     
  11. azblazor

    azblazor 1/2 ton status Premium Member

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    Thats not good about Jim Bigley's TheDieselPage, he has always seemed pretty straight forward. Hopefully it was just a mistaken idenity. Try this one: http://www.dieselplace.com/forum/index.php a lot of the same guys hang out there.

    I'll do some more poking around on the resistor issue.
     
  12. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Well, I got a replacment PMD today. THis one works much better.
    However, it doesn't solve my original problem, which is the massive surging then a back-out and buck.
    I did check my original resistor was a 5, so the 5 I got with my extension harness should be fine an no pump timing nessesary.

    So, what next. You say i'm due for injector rebuilds or pump rebuild? I see those pumps for 400-500 or so, and I see rebuilt pump kits for $120 or so. Is it hard to rebuild by own pump? Is that the likely cause of the issue.

    What about the injectors? How are those rebuilt. I see sets of rebuilt injectors for $230 or so and brand new bosch injectors, full set for $300 or so.
    The truck does have 200k on it, and from what your saying, I should probably have a new pump and injectors anyhow, so in the long run, it's not really money wasted, right (looking for reassurace :haha:)

    Or should I just take it to a dealer, one where I know they have a decent diesel mechanic, and have them at least just diagnose it for $80? The thinking here is it could be some stupid little thing that I don't have the ability to test for or diagnose myself.
     
  13. imiceman44

    imiceman44 1 ton status

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    At 200 you most probably need a rebuild of the injection parts.
    Now I know most places charge for testing then if you buy from them they deduct it from the purchase price, if the dealer does that then the $80 is not wasted.
    I would rebuild the pump using a kit, but then again I rebuild everything I can myself, you can also have someone rebuild it for you, Rene (TRustyK5) has good experience with a company, I think it's accurate diesel?
     
  14. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Is that something a "normal" wrencher can do, rebuild the injection pump? Or are there special tools and tolerancing type stuff required.
     
  15. imiceman44

    imiceman44 1 ton status

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    I haven't done that yet, but I have done pretty much everything else, and talking to someone that does rebuild them, he said I should be able to do it.
    The injectors is another story, I don't think I can without the proper tools, but the IP is doable.
    :D
     
  16. azblazor

    azblazor 1/2 ton status Premium Member

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    I would not rebuild an injection pmp myself. There are very critical tolerances. Testing machines are also necessary for pumps and injectors to be performance verified after rebuilding. Not to say you could not rebuild one and have it work OK. I am on several diesel forums and can not recall reading about anyone rebuilding their own injector pmp - again - not to say someone has not done it sucessfully.

    I have replaced IPs and injectors, and even professionally rebuilt IPs don't always perform as advertised. A warranty is a good idea.

    I was also not necessarily saying that spending the better part of a thousand bucks was the next step. I would get on a few diesel forums and ask for ideas. I would also try to find someone locally with a scanner that can read real time sensor data when the problem is occuring. A manual trany diesel with an electronic injection pump is very sensitive to any little injection event change especially if it is a rapid change. My 02 CTD w/NV5600 can feel like a bucking horse if you let your foot wobble under the right conditions.

    I would still go over connections with a fine tooth comb - grounds and computer and sensor connections. If you could get a good recommendation from a mechanic you trusted for $80 it could be money well spent. But frankly most current mechanics don't really know anything about the 6.5 electronic controls, actually most never did and now even fewer are out there. I have some factory manuals. If it would help you troublesoot, I could PDF some pages for you and send them in email.
     
    Last edited: Apr 17, 2007
  17. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Yeah, that's what I kinda thought. I saw some websites out there with huge machines that calibrate and test the IP. While I think it's possible, and as much as I wanna try, I don't think it's a good idea.

    I checked and even replaced some of the grounds and connections. I'm an expert wiring guy, I wired my K5 from scratch. It's not that for sure.

    I think it's going to the dealer up the road here tommorow for diagnostics. I still think it's the IP, but in case it's something stupid somewhere, I hate to spend $500 for an IP and still have an issue. They used to have a good 6.5l guy there, I hope he's still there. He came recommended many years ago, I think it was 1999, when the IP took a crap, and they replaced it under warranty at 45k. He seemed a very knowledgable guy, he wanted to talk to me when I picked up the truck, which is amazing, usally they don't let you near the dealer techs. I still have the repair order with his name on it, so hopefully he's still there.

    I should try to get my buddy here with his Tech II again to do some road testing, but he's gone for 2 weeks now, and I really don't want this truck down for another 2 weeks. I need to get it fixed, this week.

    Thanks for all the help guys!
     
  18. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    I made a nice long post over there, after searching around for a few hours yesterday morning. No responses yet. It's skipped down to the bottom of the page now. Perhaps some 73k5blazer tore up all the diesel forums or something a while back.

    Anyhow, I ran some more diagnostic procedures I could find. None of them point conclusivly to the IP, but all of them say the IP is pretty much it. There's no vacuum leaks, no fuel leaks, lift pump is working, turbo is working, wastegate is working, all ground and electrical connections have been checked/replaced.

    So I think I'm gonna go ahead and replace the IP. Being it has 200k on it, it should probably be rebuilt/replaced anyway, right?
    The only other thing I think it could be is an injector. Is there a diagnostic procedure for those in the manual? Wouldn't one of those pop a code, I would think?

    Yeah, if you can send me the removal and installation for the IP, and if there's any troubleshooting procudure for the injectors aside from replace, that would be great. I'll PM you my address. Thanks alot for all your help.
     
  19. azblazor

    azblazor 1/2 ton status Premium Member

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    I posted up a response over there for you. Very good write up by the way. I would try to adjust the TPS - its possible that it could be affecting the feedback loop. I'll try to PDF you some pages out the factory manual tonight.
     
  20. azblazor

    azblazor 1/2 ton status Premium Member

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    I think you probably need new injectors and even a new IP based on your mileage. But I think bad injectors usually result in general poor performace/power and bad spray patterns and dribbling that burn holes in pistons.
     

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