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Gmc 3500 6.5l - questions

Discussion in 'Chevy Trucks' started by EGLC, May 18, 2011.

  1. EGLC

    EGLC PlowSite.com Addict
    Messages: 1,733

    I'm looking at a MINT GMC 3500 only issue is the 6.5l diesel motor. It has 50k miles on it and is in great shape, only thing that scares me is the motor.

    Anyones thoughts? Are they as bad as I have heard? It did have a new fuel injector pump installed recently. Is there anything specific I can do to it to help it???

    Bottom line is it worth messing with or is this going to be a money pit
  2. pmorrissette

    pmorrissette Senior Member
    Messages: 175

    IMHO, the 6.5 is a good solid motor.

    I had one in 94 K3500.

    It is not a powerhouse, but it does OK.

    Potential issues:

    - Oil pressure sending switch (the power to the lift pump goes via this switch, good idea to change it if not done recently)

    - Fuel lift pump (they can wear out over time and not provide enough pressure to the injector pump. Also a cheap item to change out if not done yet).

    - Turbo waste gate mechanism (the vacuum system can be unreliable causing loss of boost pressure, really easy to change out to a spring mecanism)

    - Starter motor (it's a big heavy engine to crank over, and wears out the starter rather quickly, local rebuilds are pretty cheap and do wonders and increasing cranking speed which ease up starting)

    - Being an older motor, it isn't build for low sulpher diesel (sulpher was used to lubricate the injector pump & injectors), so it's a good idea to add some lubricant to the fuel. I would always dump in 1 quart of inexpensive non-detegent motor oil before filling the tank.

    Suggest you join DieselPlace, they have a dedicated forum on the 6.5 with TONS of valuable info.
  3. Dewey

    Dewey Senior Member
    Messages: 438

    I wouldn't touch it with a ten foot pole...... I have one that I have put 5 injector pumps on and has had multiple of other issues.... run don't walk away !!! PS mine has 107,000 miles with the motor replaced at 48,000
  4. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    6.5 is a great engine. the people who have had problems with them, particularly injector pumps, just have lousy mechanics, and/or take them back to the dealer for work. Not many quality 6.5 techs out there.
    Best truck I've ever owned was a 97 3500 with a 6.5. I did every aftermarket upgrade available, no it's never going to be a racer like a tuned Duramax, but I'd say mine with a computer, exhaust and bigger turbo was on equal footing with a stock Dmax.
    I whipped the crap out of that thing for ten years, and it never once complained. If you do some research on it you will find out the true story behind this motor, and the reason it has a bad reputation, which unfortunately Dewey apparently found out the hard way. Many of us actually like the undeserved bad reputation, because it keeps the prices down.
    thetruckstop.us 6.5 forums is probably the best place I have found, many of the dieselplace crew migrated there.
  5. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    to answer your question, there are many things you can do to preserve it and make it last longer. I'd say the number one most important thing is to get the PMD off the injector pump and remote mount it on a cooler behind the front bumper. That combined with the new injector pump will guarantee no further problems in that department. The unfortunate decision to mount the PMD on the injector pump resulted in premature PMD failure, which is the leading cause for the misdiagnosis of a failed injector pump.
  6. EGLC

    EGLC PlowSite.com Addict
    Messages: 1,733

    I don't want to mod the truck, this is a dump being used for landscaping....

    How hard is it to move the PMD? What else do you suggest doing? How much money am I looking to get this solid....to a reasonable extent?

    Like I said this is all about ROI this isn't going to be a toy.
  7. BlizzardBeater

    BlizzardBeater Senior Member
    from Maine
    Messages: 420

    If you can get it cheap enough, theres really nothing wrong with them. They are a bit underpowered when compared to todays diesel motors but were good nonetheless. The biggest thing to make sure is done is to move that PMD so it cools off. The post about the starter motor is actually a rather good idea as well. Like was said before, they really run a lot better and last longer if you religiously use a proper additive.
  8. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    you can buy a kit for well under $100 with a harness and a finned aluminum cooler. Ebay has them, or pm me for a contact at the truckstop. You don't even have to remove the pmd if you have another one to use. Just unplug the harness from the pmd, put the 6 foot harness inline, remove the front plate bracket and drill a couple holes to mount the cooler through the vent hole on the bumper, then put it back on. Feed the harness to it through the drivers side of the radiator support somewhere, being careful to grommet it so it can't wear thru and also keep it away from the fan.
  9. Theshoemaker

    Theshoemaker Senior Member
    Messages: 210

    As said above: the pmd issue is not a big hurdle as long as you relocate it to a good spot. I have gone thru a few pmd's and the key to sucess is to keep them cool!! As long as they get air over the heat sink fins, it should be ok. As far as engine reliability, i had 240K on mine and it is still running today, Granted I did MAINTAIN it responsibly and went thru a few pmds and 2 injection pumps. Like you said, you are not going to hotrod it so i do belive if you maintain it like anything else, then it will go a long way.
  10. Philbilly2

    Philbilly2 PlowSite Veteran
    Messages: 3,766

    6.5L is a good motor. best part about them is they are great on fuel.

    6.5L are about the most fuel efficent plow trucks out there.

    These motor's got a bad wrap due to the PMD that was misdiagnosed as a bad injection pump. As long as you treat the motor well, it will treat you well.