Volume 1 Issue 1 - Diesel Articles

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6.5 Diesel Suburban Renewal
6.5 PMD Strikes
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Project 6.5 Diesel Suburban Renewal

When the 6.5s were built, there really was no horsepower race and 190 HP was, well, “not bad”. Compared to the Duramax, 190 HP doesn’t measure up and, as we all know, power really does matter. To make things worse, the 6.5 problems have not been limited to less-than-desirable power; they have also had reliability issues – as we experienced for ourselves in the course of this rebuild. Perhaps, in a quest for more power and reliability, you have searched some of the big name diesel upgrade companies only to conclude that there are not any products out there that will mollify the frustrations you have experienced with your 6.5. There are, however, solutions that will make these trucks perform like they should – at a price that can’t be beat.

maxxTORQUE, seeking to get the word out about the hidden value of these vehicles, hooked up with Heath Diesel Power (HDP – www.heathdiesel.com) and asked them to build up a common 6.5L truck. Bill Heath, the owner, was delighted to participate noting that “the 6.5 is much-maligned due to the problems experienced with them beginning with the introduction of the 1994 models that featured the Stanadyne fuel injection system.”

Trucks were either running screwy or conking out. Dealers were ill-equipped to offer effective solutions. In many cases, trucks that experienced failure of only the pump mounted driver (PMD) module – we’ll address this item soon – were subjected to the standard GM diagnosis flow chart that suggested replacement of the entire fuel injection pump, including a fresh 6.5 PMD. The result of the repair was a truck that might run well for a year or so, only to have the same issue resurface. It did not take too many “incidents” like these for the 6.5s reputation to tailspin.

The good news about a 6.5 with a reputation for being less-than-reliable is that there are straightforward and relatively inexpensive steps that will transform the vehicle into a fully reliable and powerful vehicle. And, because of the bad rap, owners can be on the road with an upgraded, reliable and powerful diesel truck for under $10,000. When you consider the price of a new rig, it is easy to see why many of us have opted for a 6.5 and avoided those always-fun-to-make $500-plus monthly payments.

Unfortunately, 6.5 owners are often unaware of the upgrades available to transform a “frustration” into a reliable and powerful work truck. A few times up a steep grade in a stock 6.5 with a trailer in tow and you might find yourself thinking, I should have mortgaged the house, as late-model trucks pass you by. The answer, however, isn’t dipping into your children’s college fund – that 6.5 has all the reliability you need and plenty of power: the answer is just a matter of helping her find it. The truth is, after a weekend’s worth of bolt-on upgrades, you will not only power up those hills faster and more efficiently, you will get to enjoy the looks on the faces of other diesel owners as you keep pace with their high-dollar rigs.

To help you envision the potential of a 6.5, Heath Diesel completed a build-up on a stock 1994 GMC 2500 4x4 Suburban. Before the build-up, the Sub was all original, including the 6.5L engine. Talk about a great vehicle to put a diesel in! Not only can you hitch up a 10,000 pound trailer, you can do it with the entire family onboard and still have room for more. Our project Suburban had 185,000 miles on it and ran great. She just needed a little push in the right direction to unleash some hidden abilities.

6.5 Diesel PMD Strikes

The guys at Heath had a pretty good idea of the kind of power our project Sub would deliver on the chassis dyno; however, they suggested that before any dyno testing, we ought to drive our Sub in order to gain some perspective on her abilities and personality. Doing so would allow us to be better able to appreciate the value of the upgrades. As it turned out, our time on the road proved to be valuable indeed. We took turns behind the wheel, sharing our impressions of the vehicle. We were impressed with how quiet and smooth she ran and appreciated the great utility of the Suburban.

Out of nowhere, the engine stopped – just stopped – cold. Not quite as abruptly, we rolled to a stop along the roadside realizing we had – most likely – just experienced a real-world 6.5 PMD failure. After a few tries, the engine started up like nothing had ever been wrong. If we hadn’t known about the diesel PMD issue the 6.5s tend to suffer, we would have been scratching our heads wondering what had caused the stall. Fortunately, it happened on a quiet country road on a cool Washington State day and not on some rush hour-crowded freeway... at night... in the rain. So Murphy was only half-right.

The Heath guys suggested – and we agreed – that before any attempt at dyno pulls, and in order to assure a good base line performance, we should go ahead with the installation of the...

In this article...

  • 6.5 PMD Strikes
  • 6.5 Lift Pump
  • 6.5 Diesel Exhaust System
  • HO 6.5 Fuel Injectors

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Comments (2)add comment

Chad H said:

Re: 6.5 Diesel Suburban Renewal
I was thinking of buying a 98 gmc dually with a 6.5 turbo diesel that has 138000 miles on it. I was reading your article on the suburban build up and was wondering,did GM improve any of these reliability and power issues on the later year models? Say after 98 and up? Thanks.
December 03, 2009
Votes: +0

bheath said:

Click the following link for Bill Heath's (heath Diesel) response to the above question...

December 09, 2009
Votes: +0

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Bill Heath owns Heath Diesel Power in Ellensburg, Washington. He races at Bonneville in his 6.5L Land Speed Racer whenever he gets the chance.


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