1. Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!

'98 GMC diesel diagnosis

Discussion in 'Trucks' started by mitch504, May 24, 2019.

  1. mitch504

    mitch504 Senior Member

    Joined:
    Feb 27, 2010
    Messages:
    4,034
    Location:
    Andrews SC
    A truckdriver that worked for me for about 12-14 years died recently and his family wants to sell me his beloved pickup truck. It is a '98 GMC 2500 with a 6.5 in it, and they say that it will periodically cut off while driving. It had a brand new injector pump installed about a year before he died and was running good when he died. A little internet research says that a very common problem with these trucks is that the pump drive module breaks down with heat and should be relocated.

    Have any of y'all ever run into one of these trucks doing this?

    I know less about diesel pickups than I do about most things, if you can believe it.

    Thanks guys,
    Mitch
     
  2. DB2

    DB2 Senior Member

    Joined:
    Jan 4, 2015
    Messages:
    292
    Location:
    Winnipeg MB Canada
    Does it have an electric transfer pump in the line from the tank ?
    I know the 6.2’s did and they would cause intermittent problems
     
  3. RZucker

    RZucker Senior Member

    Joined:
    Jul 7, 2013
    Messages:
    2,766
    Occupation:
    Mechanic/welder
    Location:
    Wherever I end up
    My daily work truck is a '98 K3500 6.5 Diesel with 235,000 miles. The electric transfer pump is a weak link, I change mine once a year just for grins, Transfer pump output should be 4psi minimum. If the transfer pump quits and it doesn't lose prime it will still run but you will get stumbling/surging at part throttle. I have relocated my PMD to the underside of my winch bumper on a big heat sink from Diesel Care Products. The stalling then restarting does sound like a PMD issue, the board inside will heat up and break a circuit and reconnect when it cools. There are 2 versions of the PMD, an early black one and a later grey one. IIRC the plug connectors were different, but you can get the relocate kit and a PMD as a matched set.
    By the way, a bad PMD will not set a check engine light or show on a scanner. swapping it out is the only test.
     
  4. wornout wrench

    wornout wrench Senior Member

    Joined:
    Feb 17, 2012
    Messages:
    448
    Occupation:
    Retired Heavy Duty Mechanic
    Location:
    Campbell River, BC, The Left Coast of Canada
    I have a 98 3/4 ton with the 6.5.

    I have had some problems over the years. I'm on my 4th PMD. second injection pump and second transfer pump.

    The Injection pump set a code, the PMD will not.
    I find with mine that when the PMD starts to fail it will cut in and out, just like the key is turned off and on, it can be rather violent.

    If you are experiencing random engine cut out, check your grounds. I had that problem years ago. One of the main ground on the intake manifold was loose. Truck would just die, would restart fine until the next time.
    The ground was on the right rear and the trans level tube was also bolted to it.

    A really excellent place to go for information is the https://www.thedieselpageforums.com/tdpforum/

    Lots of people there still keeping the old girls running.
     
    DB2 likes this.
  5. thepumpguysc

    thepumpguysc Senior Member

    Joined:
    Mar 18, 2010
    Messages:
    4,612
    Occupation:
    Master Inj.Pump rebuilder
    Location:
    Sunny South Carolina
    YUP.. they gotcha heading in the right direction.. PMD re-locate harness..
    Ya gotta have some deep pockets if u wanna play w/ a 6.5 or 7.3..
    The "good thing" about those is they still have mechanical injectors.. cheap compared to the 200.00 apiece inj. now adays.. & the 3000.00 labor to replace'm..
     
  6. mitch504

    mitch504 Senior Member

    Joined:
    Feb 27, 2010
    Messages:
    4,034
    Location:
    Andrews SC
    Thanks guys, this gives me more of where to look. I haven't seen the truck except from a distance in over a year. It was one nice truck when Fuzzy had it, we'll see how his grandson has been treating it. They want me to get it bad, to keep it in the family, so to speak. At what they are asking I should be able to fix it.
     
    RZucker likes this.
  7. wornout wrench

    wornout wrench Senior Member

    Joined:
    Feb 17, 2012
    Messages:
    448
    Occupation:
    Retired Heavy Duty Mechanic
    Location:
    Campbell River, BC, The Left Coast of Canada
    Definitely remote mount the PMD on a heat-sink.
    I also keep a spare PMD in the glove box (as with most people I know who drive a 6.5)

    I don't put a whole pile of miles on my truck anymore. Pretty much just use it for pulling my travel trailer and running stuff to the dump, picking up the occasional load of lumber.

    But I like it, pulls my 23 foot trailer no problem. It's not too bad on fuel if I keep the RPM's down which is hard because of the low gearing;)
     
  8. mitch504

    mitch504 Senior Member

    Joined:
    Feb 27, 2010
    Messages:
    4,034
    Location:
    Andrews SC
    Well, I bought it today. Before I bought it, I drove it 1.1 miles to my brother's house so he could talk me out of it, but he failed to do so. It ran and drove perfectly all the way there, and .8 miles back. I turned onto the dirt road they live on and it shut off and would not restart. The batteries were weak, so it didn't spin long.

    I walked back to their house and told them it was dead in the road, and I would give them $1800 where it sat. Fuzzy's daughter said "OK", so I went back and hooked up jumper cables and took the plastic cover off while it charged. It started up and she came and brought me the title, so I shut it off while we talked. It refused to restart so I towed it to my brother's place and went home and grilled cheeseburgers.
     
    GregsHD and Wytruckwrench like this.
  9. mitch504

    mitch504 Senior Member

    Joined:
    Feb 27, 2010
    Messages:
    4,034
    Location:
    Andrews SC
  10. thepumpguysc

    thepumpguysc Senior Member

    Joined:
    Mar 18, 2010
    Messages:
    4,612
    Occupation:
    Master Inj.Pump rebuilder
    Location:
    Sunny South Carolina
    It wouldn't start the last time because of a dead battery or something else.??
    If it sat for a length of time, get that fuel outta there.. but I don't need to tell YOU that..
    Sounds like a nice truck.. & VERY reasonably prices..{you crook, lol}
    BTW> I think I may have a PMD.??
     
  11. mitch504

    mitch504 Senior Member

    Joined:
    Feb 27, 2010
    Messages:
    4,034
    Location:
    Andrews SC
    My brother said that Fuzzy (the previous owner) had talked about relocating the PMD. When I looked I saw a Dtech PMD on a long cord just screwed to the inner fender, no heat sink or anything. I had ordered a PMD and relocate kit on Amazon the day I bought the truck. I got it yesterday and yesterday evening I unplugged the PMD on the fender, ( thinking: "Oh boy, this is going to be easy!) and plugged in the new one. I hooked up jumper cables and tried to start it. It just spun. I traced the extension cable and it was just laying on the intake manifold. My brother now thinks Fuzzy was trying to talk him into pulling the intake to plug it in. (My brother is a retired diesel mech)

    Today I pulled off the A/C compressor and steering pump and bracket and could see the PMD under the intake. It was so swollen it was cracked all up. I poked it with a long screwdriver trying to unplug it and the housing just crumbled. I got it unplugged and fished the plug out from under the intake. I plugged it into the extension cable that was already there and the old girl fired right up and ran great. I let it idle about 10 minutes with the new PMD just laying on the fender, and it was too hot to touch. I grabbed the heat sink and screwed it on and the temp dropped quickly. I just wired it in the airflow from the fan and drove home. The truck ran and drove great!

    I am thinking about mounting it on the side of the battery box support. I thought about mounting it under the bumper, but I am afraid it would be full of mud soon.

    Do any of you know what the fuel capacity is on a '99 C2500 long bed old body style with a 6.5?
     
  12. RZucker

    RZucker Senior Member

    Joined:
    Jul 7, 2013
    Messages:
    2,766
    Occupation:
    Mechanic/welder
    Location:
    Wherever I end up
    20171101_095319.jpg
    My SRW 3500 holds nearly 40 gallons. Mounting that heat sink in cool airflow would be the best. Mine is bolted to the bottom of my winch bumper, and it melts snow after 30 seconds of run time in the winter.
    That's my old workhorse above.
     
    Last edited: Jun 1, 2019
  13. thepumpguysc

    thepumpguysc Senior Member

    Joined:
    Mar 18, 2010
    Messages:
    4,612
    Occupation:
    Master Inj.Pump rebuilder
    Location:
    Sunny South Carolina
    Don't forget Mitch, theres a thin heat sink gasket between the PMD & the metal heat sink..
    I think, its been awhile, that its a 1 way heat blanket.??
     
  14. mitch504

    mitch504 Senior Member

    Joined:
    Feb 27, 2010
    Messages:
    4,034
    Location:
    Andrews SC
    Yeah, my kit came with no info. I hope it doesn't have to be turned a certain way. I couldn't see any difference in the 2 sides. But I must have gotten it right, it sure worked to draw off the heat. I was thinking to put it where the fan flows over it, since it may idle a while jumpstarting, etc.
     
  15. mitch504

    mitch504 Senior Member

    Joined:
    Feb 27, 2010
    Messages:
    4,034
    Location:
    Andrews SC
  16. mitch504

    mitch504 Senior Member

    Joined:
    Feb 27, 2010
    Messages:
    4,034
    Location:
    Andrews SC
    Ok, stupid question time!!

    How do you tilt the seat forward? If you pull on the seat back a few times, it will suddenly unlatch and lean forward. I can find no rhyme or reason for when it will unlatch, and I can't find a handle at all. There is a latch that I can feel when it is leaning forward, but nothing I can feel when it is back.:confused::oops:
     
  17. RZucker

    RZucker Senior Member

    Joined:
    Jul 7, 2013
    Messages:
    2,766
    Occupation:
    Mechanic/welder
    Location:
    Wherever I end up
    No latch handle on mine, you just tilt it forward. I think it has one of those "inertia" latches like the seat belts.