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Let's build this 6.5 section up

Discussion in 'GM 6.5 Diesel Engines' started by GregAbell, May 14, 2008.

  1. GregAbell

    GregAbell Recruit

    May 9, 2008
    Itasca, IL
    Eventually, a newbie is going to come in here asking if he should buy a certain truck, and what he needs to look at before buying. Feel free to add to, modify, or whatever.

    Apply whatever you normally would check on a used vehicle – How’s the body? Does it pull when you brake? Are there any vibrations at speed? Are the tires wearing evenly? Etc.

    Diesel specific checks:

    When first checking the truck out, start it up - does it start easily, or does it struggle to start with white exhaust smoke for a little bit (but goes away fairly quickly)? Not all that bad to repair – it’s just the Glow Plug section, and you can use the hard starting problem to get the seller lower on his price.

    If after starting the truck, if it continues to exhaust white smoke, there might be a Head Gasket problem (or possibly even a cracked head) – BE CONCERNED!

    After it starts, check the upper radiator hose while cold. As the truck warms up, the upper hose SHOULD NOT get hard. If it does, it means that combustion gases are getting into the cooling system - RUN AWAY - FAST!

    Remove the oil fill plug and check for blow-by. If it's bad – BE CONCERNED!

    Look at the rod for the Wastegate (connected to the Turbo). At idle it should be sucked into the canister with so much force that you can't move it. If it's not, it might cost you over $150 to repair the vacuum problems - Vacuum Pump, Wastegate Solenoid, Vacuum Lines, and Wastegate Actuator are the parts involved on an "F" code engine – an “S” code engine will have these items as well as an EGR section that will utilize the vacuum section. Of course, it could just be that a vacuum line has become disconnected, or just the Solenoid ($30) has gone bad, so a problem in this section shouldn’t rule a truck out of consideration – it just gives you more ammo to talk the seller down in price.

    These trucks received an undeserved (I think) reputation for having a lot of Injector Pump (IP) problems, when in reality, the problem was more often than not, just the electronics that controlled the IP (a little electronic box that’s the size of a deck of cards). Don’t get me wrong – the Injector Pump CAN go bad, just not as often as people thought – there was a lot of misdiagnosis on the dealer’s part when these engines were introduced. Look at the engine on the Driver’s side. See if you notice a heat-sink with an electronic box about the size of a deck of cards mounted to it. If so, this was an attempt by somebody to correct this problem, but they still mounted it in the hot engine compartment. You will need to get this out of the hot engine compartment (it may already be too late – the electronics inside might have “cooked”). The factory location has this “box” (PMD – Pump Mounted Driver) mounted right on the IP. Again, it can “cook” in that location too. Heath Diesel offers a remote FSD (Fuel Solenoid Driver – it’s NOT pump mounted anymore) that corrects this problem. It might seem expensive (~$550) but this is the only solution I know of that has a 7 year warranty (there was a poll on another site to see if anybody had one of these fail, and NOBODY had reported a failure - EVER). When this PMD/FSD starts going bad, you’ll lose cruise control; the truck will buck; stall; refuse to run – you could be stranded anywhere that it decides to “give up the ghost”. You can just replace the “box” for ~$250 or so, but what kind of warranty are you going to get – 1 year (if even that long)? There’s no reason in my mind not to pony up the money in the first place and have the known problem area addressed once and for all.

    These trucks also have an issue with the fuel delivery system. They use the Oil Pressure Switch (OPS) to feed the power to the Lift Pump (LP – just another name for a fuel pump). When everything was new, and within specifications, this system probably worked well. The problem arises when components age – they tend to draw more power. When the LP draws more power than the OPS was designed for, the contacts inside of the OPS can’t handle the load (your oil pressure gauge will probably continue to work normally), and the LP will stop working. If there are no fuel leaks in the system, the IP can create enough suction, so that the truck will continue to run. If you aren’t “in tune” with how the truck “should” be running, you might not even know that the LP isn’t working. The LP is mounted on the frame rail underneath the truck about where the driver’s seat is located. While the truck is running, you can grab the LP and feel if it is running or not. You can correct this factory deficiency by having the OPS close a relay, and having that relay control the power going to the LP.

    There have been some other electronics issues besides the PMD/FSD and OPS/LP problem. On the passenger side battery, there is a double-positive cable connection that has given people problems over the years. Some people have used “all thread” along with washers and nuts to correct this problem. Another problem area, is that somebody could have damaged (or otherwise disconnected) some of the grounds that the truck requires. Check that the ground is still connected on the rear of the passenger side head especially (since that one seems to be the most over-looked).

    Both batteries should appear to be identical as to manufacturer and age. The system is only going to be as good as the weakest battery in the system.

    If you’ve done your own “wrenching” on gas engines before, you shouldn’t have much of an issue working on the 6.5 engine. You won’t have to “reinvent the wheel” here. Almost any problem that you will encounter will almost certainly have happened to somebody before you. If you post up what your problem is, you should receive enough responses to keep you checking on what the root cause of your problem is, along with what the solutions have turned out to be.
    Last edited: May 14, 2008
  2. jmiller

    jmiller Recruit

    May 6, 2008
    Lake Villa, CRIL
    Great article, it hits the major things.
    Addition / augmentation:

    Battery and ground connections: Dirty or loose connections are a key source of all types of "Issues".

    Battery cables, remove all the cable bolts along with the puck from the cross over cable at the passenger battery and check for corrosion between the terminal and the bolt / puck. Clean both sides of the terminals and the bolts, coat them with anti corrosion gel before assembly.

    Caution on the use of all thread and over tightening could damage the battery terminal. (it is only lead)
  3. jmiller

    jmiller Recruit

    May 6, 2008
    Lake Villa, CRIL
    Not too many go fast things. 6.5 is considered light duty were dmax, cummins etc are a heavier duty.

    Things will typically break if someone gets carried away with power adders on a 6.5.

    Don't mis understand, there are things out there for increasing the 6.5 power but you won't be able to turn it up crazy like the newer enignes.
  4. knkreb

    knkreb The Bus Driver is here!

    May 3, 2008

    You can, but no cryin' when you break it :cryin:
  5. monel_funkawitz

    monel_funkawitz Recruit

    May 7, 2008
    When buying a used diesel, especially if it is your first, try to avoid buying one that does not run, even if the owner claims something simple, until you are experienced with diesels. Something that sounds like a simple problem can be expensive. When you are familiar with diesels, a problem vehicle can be a good purchase if you know what you are looking for. Keeping yourself informed and having knowledge will be an extreme benefit.

    Many people that are not familiar with diesels will shy away from high mileage diesels. Fact is, my 1997 6.5 runs just like it did when new, and it has 202,000 miles on it.

    When I got my truck (Which was my first diesel that I have personally owned, but not worked on) everyone thought I was crazy getting it as a daily driver. I don't tow, I don't haul, just drive to work. Best investment I ever made. Long story short, a diesel is a good choice for almost any application. I'll never go back to gas if I have any choice. Diesels however, are not for everyone. They don't like neglect, and you will have to live with turbo whine, diesel smelly hands from the pumps, the fact that not everyone will have every part on hand, and funny looks from people at parts stores.

    Auto Zone - Ok sir, you need an air filter for a 1997 Silverado? What engine?
    Me - 6.5 Diesel
    Auto Zone - :confused: 6.0? What is it again? Oh, here it is, at the bottom.
  6. JMJNet

    JMJNet Recruit

    May 6, 2008
    Richardson, TX
    ALWAYS, relocate the PMD from inside original location or intake or fender well to outside the engine mounted on heatsink.
  7. DMitch

    DMitch Recruit

    May 7, 2008
    When you make an appointment to look at the truck, tell them that you want to hear it start cold. Sometimes a cold motor will show symtoms that a hot motor will not.

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