The Diesel Page
6.5L Turbo Diesel
Volume II
Performance, Fuel Economy & Maintenance

Now Available! - $24.95 + USPS Priority mail.


6.5L Turbo Diesel Volume II - Copyright 2018

The 6.5L Turbo Diesel Volume II represents a collection of all of the important 6.5L diesel related articles, tech columns and product reviews that were published by The Diesel Page between 2001 and 2007. What you'll find here are time-tested and proven methods, techniques and strategies that will increase 6.5L TD performance, fuel economy and reliability. This 160 page 8-½" x 11" book includes 39 articles and 291 B/W photos/graphics, which cover the 1992-2000 6.5L diesel equipped GM vehicles.

Our focus here at The Diesel Page has always been to expand the knowledge base for these engines and to improve ownership satisfaction. Improving performance, fuel economy, drive-ability and reliability are all important, and we strive to help 6.5L diesel owners achieve those goals.

This book includes articles that will help the first-time buyer choose the right 6.5L diesel equipped vehicle, as well as understand the basics of diesel ownership. In addition, we have included 5 articles covering performance-built (and customized) 6.5L engines. The sky is quite literally the limit, when it comes to customization and degrees of performance. We've proven the 6.5 can compare favorably with the stock Ford & Dodge diesels produced some years ago. These articles contain the hard data.

Fuel economy has become a hot topic among diesel owners since the cost of diesel fuel rose above $3/gal in 2005 and then nearly $5/gal in 2008, and fuel economy is among the top three reasons why people buy a diesel equipped vehicle. We've added a new article to this book that will help you learn more about 6.5L fuel economy.

New in this book is a discussion about custom turbochargers and their effect on performance - with chassis dyno and Pull-Off performance tests to support what you read here. I expect turbocharger selection will become more important in the near term in defining the power potential of the 6.5L Turbo Diesel.

The final five articles contained in this book collectively explain how to overcome the primary hurdles when converting from electronic fuel injection to mechanical fuel injection. When combining this information with a set of injector fuel lines, throttle pedal assembly, throttle cable & brackets and DB2-4911 fuel injection pump, you'll be able to make the switch and perhaps improve reliability. These five articles are not a step-by-step guide to completing an electronic to mechanical fuel injection conversion, but they will provide solutions for the biggest challenges. We've been involved in several of these conversions, so we encourage you to contact us to help fill in the blanks as you work through a conversion.

All of us here at The Diesel Page hope you enjoy this book, and perhaps more importantly, hope you learn how to improve your 6.5 in any or all areas you feel your truck or Suburban needs improvement in. We want to see you succeed!     TDP

Note: This volume is available separately. Please see the Member's Area page to see what articles are currently online and available to current subscribers. Many of the articles included in this volume are no longer available online.


  1. Buying a Used GM 6.5L Diesel
    What Year 6.5 is best? What to look for?

    I've answered a lot of questions through the years concerning the GM diesel engines. The hardest question goes something like this: "I'm considering buying a 199x Chevy with the 6.5L turbo diesel. I've heard some bad things about this engine, and I don't want to buy into more problems. I want a diesel, but is this a good engine?" That's a tough one. Go here for the answers.

  2. Diesel Primer
    Getting acquainted with your GM diesel.

    Ok, you just bought a 6.5L turbo diesel truck or Suburban. You might be wondering what you need to know about diesel engines to get the fuel economy, power and reliability diesel engines are noted for. What you'll find here is essential information specific to GM diesel engines that could help eliminate some of the problems experienced by new diesel owners, and help you get more out of your "new" diesel engine.

  3. DS4 Electronic Fuel Injection Pump
    Warranty Replacement Policy #00064D

    The new DS4 electronic fuel injection pump warranty was increased to 11 years or 120,000 miles (193,000 km). The 11-year time schedule begins on the date when the vehicle first went into service, and you do not have to be the original owner. This tech page should give you a bit of insight into how to protect yourself and obtain all of the warranty coverage you are entitled to.

  4. 6.5TD Power Project Update
    Seven Years & 200,000+ Miles

    As the sub-heading indicates, the 6.5TD Power Project truck has accumulated 200,000+ miles in seven years. This article discusses the total engine mileage, performance issues and service history since accumulating 200,000+ miles.

  5. Power by Design
    Performance 6.5TD

    Imagine a 6.5L Turbodiesel that incorporates just about every power product known to exist, and many more custom touches that take the electronic 6.5 to a whole new level. This story is about modifying the electronically fuel injected 6.5TD to produce huge horsepower and torque.

  6. Electronic 6.5L TD Power Project
    1995 Chevrolet Suburban LS K2500
    Part I: Down, But Not Out!

    This story is about a quest for more power, improved engine cooling, and increased durability for the electronic 6.5L Turbo Diesel.

  7. Electronic 6.5L TD Power Project Part II
    Building a more durable and more powerful engine.

    18:1 pistons, splayed main caps, and balancing & blueprinting allow for a more powerful and more durable 6.5L TD engine. Follow along as we show you the improvements incorporated into the engine shortblock.

  8. Electronic 6.5L TD Power Project - Part III
    Building a more durable and more powerful engine - Final Assembly.

    This is the third article in a short series documenting an engine project striving for improved performance and reliability from our 1995 6.5 TD Suburban LS K2500. In a previous segment, we discussed the machining operations performed to prepare the engine block for this project as well as the mechanical configuration that was selected. The mechanical configuration was completed by selecting Kennedy Diesel 18:1 pistons, ARP head and main studs and a Phazer gear drive. Follow along as we show you the final steps in assembling our electronic 6.5L TD Power Project engine.

  9. Phoenix
    A performance 6.5 rises from the ashes.

    There were a couple other trucks that ran the hill during the Diesel Day Pull-Off, here in Montana on September 7th, 2002. A 1996 6.5TD GMC K3500 Crew Cab did a pretty fair job on the hill, managing 45-mph at the one-mile point from a dead stop on the 6% grade with a 10,000-lb trailer. Unfortunately, this level of performance came at a price. Find out what went wrong and how we built a better 6.5.

  10. 6.2/6.5 Main Cap Stud Girdle Kit

    Some 6.2/6.5 engine blocks have developed cracks that originate from the outer main bearing bolt holes. The Stud Girdle Kit from Diesel Services Group was designed to help solve this problem. By joining the center three main-webs together, dynamic forces are better contained and the studs eliminate the spreading force put on the block while torquing the main cap fasteners.

  11. The Stanadyne DS4 Electronic Fuel Injection Pump

    Come with us to a Stanadyne authorized service center and learn the basics of injection pump service, and see how the pumps are tested and calibrated before being sent out to a customer. This is an interesting look at the central component in the GM diesel injection system.

  12. Fuel Solenoid Driver Calibration Resistor

    Back in March of 2000, The Diesel Page published a technical article showing how to produce a variable boost pressure controller for the electronically controlled 6.5TD vehicles. That same article also discussed increasing/decreasing fuel delivery of the DS4 electronic fuel injection pump by varying the FSD calibration resistor value. This new article expands on the relationship between calibration resistor values and DS4 fuel delivery. More power? Improved fuel economy? You decide.

  13. DSG 6.5TD Engine Oil Cooling Kit

    Anyone who has owned a 6.5 for any length of time has had to deal with leaking engine oil cooling lines. Because of age-hardening and countless temperature cycles, all factory oil cooling lines eventually begin leaking at the hose joints. The braided stainless-steel flexible lines and leak-proof hydraulic fittings included in the DSG kit should offer a permanent solution to this age-old problem, and the new high-efficiency engine oil cooler should help to reduce oil and engine temperatures.

  14. 6.5TD Fan-Clutches
    Engine Cooling Solutions

    Cooling the 6.5 requires a systems approach. We've talked about the importance of a clean radiator, 130-gpm water pump/dual thermostats and other system components that improve engine cooling. One often overlooked (but equally important) component in the cooling system is the ubiquitous fan-clutch. Kennedy Diesel sent us one of their new re-calibrated 6.5 fan-clutches last summer, which is designed to engage sooner and improve engine cooling. This gave us an opportunity to evaluate the fan-clutch through an entire summer towing season and consider its effect on engine cooling.

  15. 6.5TD Cooling Solutions That Work

    Cooling the 6.5 requires a look at all of the cooling system components (and some components not usually thought of) when trying to solve a temperature problem. Certainly, the fan-clutch is an extremely important part of the system, but individually and collectively, the different cooling system components we'll discuss here can and will make all the difference in helping your 6.5 keep its cool.

  16. 6.2L/6.5L Fuel Economy
    Cylinder Heads & Ricardo Comet

    The 6.2L diesel engine was introduced during a time when the world energy market sent fuel prices skyrocketing. While it may surprise you, gas & diesel pump prices during the early 1980's were actually higher than they are now - when adjusted for inflation. GM's 6.2L diesel was designed and developed for tight fuel supplies and high pump prices, and we may need to revisit the 6.2/6.5 to help provide a solution to the high fuel costs we're seeing now. The early light-duty 6.2L diesel powered trucks would consistently deliver 22-24 mpg when driven conservatively, while the later 6.5L Turbodiesels produced 5 or more miles per gallon less. Why is that? The answer to that question is what we're investigating this time.

  17. The Last 6.5 Engine Oil Cooling Lines You'll Ever Need

    The last 6.5 engine oil cooling lines you'll ever need are already installed on your truck. Follow along as we show you a home-grown repair for leaking lines, which could help you avoid spending $150+ for replacements.

  18. Improving Cold Starts
    for Electronic 6.5 Diesels

    The AC-60G glow plugs are the current GM recommended replacements for all 6.2L and 6.5L diesel engines. However, these plugs are somewhat cooler when compared to the older AC-9G and AC-11G plugs, which can affect cold starting. Extending the initial glow cycle improves cold starts, which can be important when using "cooler" glow plugs or for any situation when longer glow cycles improve starting. This procedure explains how to increase glow cycle time in all 1994 and newer electronically controlled 6.5L diesel equipped vehicles.

  19. Manual Glow Control for the Electronic 6.5TD
    Extending the Glow Cycle for 18:1 Compression Engines

    As the weather turned cooler in the late fall of 2005, we learned that our 18: low compression engine needed more glow cycle time to produce quick and clean cold starts. This article illustrates a simple and inexpensive modification designed to provide manual control for the electronic 6.5 glow system.

  20. Air Conditioning Service
    Converting an R-12 system to R-134a
    Servicing an existing R-134a System

    Part of the mystery in servicing automotive air conditioning systems for most people is a lack of understanding in the technology. While it does require specialized equipment and training to know all that is knowable, acquiring a basic understanding of what the various system components do and learning how they work together to produce cool air inside your vehicle will help in maintaining your A/C system - whether you do the work yourself or choose to hire the professionals. In addition to learning how to evaluate and recharge existing R-134a systems, we'll also show you the basics of converting an older R-12 system to R-134a.

  21. 6.5TD Fuel Filter Maintenance Tips

    Changing the 6.5TD fuel filter is a routine procedure that has been covered before (in the 6.2/6.5 Diesel Troubleshooting & Repair Guide). However, we recently learned about a potential problem that could contaminate your fuel system or might help explain some of the chronic fuel injection pump failures we hear about.

  22. 6.5L Diesel Alternator Pulleys
    How To Improve Tachometer Accuracy

    The tachometer used in the 6.5 diesel trucks and SUV's derives its signal from the alternator, which means varying the diameter of the alternator pulley will affect tachometer accuracy. With a plethora of pulley diameters available for these GM alternators, it's easy to get a replacement with the wrong diameter pulley. What we'll do here is show you how pulley diameter affects tach readings, and explain how to improve tachometer accuracy.

  23. Serpentine Belt Tensioner

    The serpentine belt tensioner/pulley assembly is something that we don't give a lot of thought to, but is one of those essential parts that can leave you stranded by the side of the road if it fails. This story discusses common problems and suggests ways to overcome potentially stranding situations.

  24. Chains or Gears? Which is Best?
    6.5 Timing Set Pros & Cons

    What are the advantages and disadvantages of using a DSG gear-drive timing set? Let's consider this question, and have a look at some of the related issues involving the 6.2/6.5 gear and chain timing sets.

  25. Bypass Cooling For the 6.2/6.5

    The concept for "bypass cooling" has been around for years, and someone usually brings it up here in The Diesel Page about once a year. I'm not a fan of re-routing coolant through the engine in an effort to improve cooling. It may actually cause more harm than good. Go here to find out why.

  26. SOL-D DS4 Solenoid Driver

    Product Review: The SOL-D module from RemarQ is a complete redesign of the original Stanadyne FSD (Fuel Solenoid Driver) module using automotive and military grade Mosfet power transistor technology. We're interested in solutions to problems. Certainly, any innovative product deserves our full attention which promises to address the FSD related stalling issues affecting the electronically fuel injected 6.5L diesels. Is the SOL-D an improvement in reliability? Go here to learn more.

  27. Texaco/Havoline Dex-Cool
    Engine Coolant Facts

    GM made the switch to the new orange-colored Texaco/Havoline Dex-Cool in the 1996 model year due to its longer service cycle, longer water pump seal life, high temperature aluminum protection, and a higher coefficient of heat transfer. Recently, a bit of a controversy has developed concerning engine and cooling system corrosion involving some GM vehicles using Dex-Cool long-life coolant. This article looks at the facts from both sides of the issue, and discusses whether we as GM diesel owners need to be concerned.

  28. BD TorqLoc
    Electronic Torque Converter Lock-Up Control

    The BD TorqLoc provides additional driver control of GM's 6.5TD and 4L80-E automatic transmission by providing automatic and manual operation of the lock-up torque converter. Improved engine grade-braking and lower transmission temperatures are things all owners can appreciate while towing, and this is what the BD TorqLoc was designed to deliver. Go here to learn how to install and use a TorqLoc.

  29. Hydraulic Brake Booster

    All of the GM diesels from 1982 to the present use a hydraulic brake booster. Find out what is involved in changing a brake booster, and where to get the best prices.

  30. Axle Swap
    6.5TD Project Truck Gets a GM 14-Bolt Full-Floater

    If you can't get it to the ground, doesn't matter how much power your engine makes. The truck's original 14-bolt semi-float rear axle with 9½" ring gear finally reached the end of the road, and had to be replaced. The combination of 240,000 miles (already rebuilt once) and living behind the 6.5TD Power Project engine for 100,000 miles finally took its toll. We chose to upgrade to a GM Corporate 14-bolt full-floater with a 10½" diameter ring gear.

  31. Randy's Ring & Pinion
    Rebuilding GM's 9½" Corporate Rear Axle

    We had to dump the original half-ton 10-bolt rear axle in our latest 1989 Chevy K1500 project truck. The 8½" diameter ring gear and 1330 U-joint pinion yoke were deemed not up to the task when twisted by more than stock power. The best replacement axle turned out to be GM's 9½" 14-bolt semi-floater for this six-lug application. Once acquiring the 1997 model-year axle, we visited the experts at Randy's Ring & Pinion for a professional installation of an Eaton Posi differential, as well as new gears, bearing and seals. We show you how to properly set up a ring & pinion.

  32. Electrical System Upgrade
    Dual Alternator Installation for the 1996-2000 6.5L TD Equipped Vehicles

    In a quest to accessorize our vehicles to our tastes with items such as lights, stereos and so on, we sometimes overlook what gives life to these accessories - the charging system. The original charging system is generally adequate for a factory-equipped vehicle, but increasing the electrical load on your factory alternator could lead to problems. There are two options to alleviate the power shortage: a custom high-output single alternator or dual factory alternators. Dual alternators were optional for the 6.5TD, which makes acquiring the factory brackets and hardware easy to obtain and install. Go here to see how to acquire the parts and make the install.

  33. Rear Disc Brake Upgrade

    The 1997 model-year GM 9½" semi-float 6-lug rear axle has been installed in our latest project truck, and to improve braking ability, we've decided to upgrade the rear drums to disc brakes. Rear discs help with two important areas - they reduce unsprung weight and they increase stopping ability. Demands on the braking system increase as vehicle speeds increase, and stopping can sometimes be more important than going fast.

  34. Rear Disc Brake Upgrade - Part II

    A rear disc conversion generally offers better braking ability - both when dry and especially when wet, weighs less than most drum brakes, sheds heat faster - more fade resistant, and discs just look way cooler... Our rear disc brake installation is now complete. Find out how they look and stop.

  35. Powertrain Control Solutions
    Electronic Transmission Controller

    The Diesel Page published its first article about converting an electronically fuel injected 6.5 diesel to mechanical fuel injection way back in 1998. Since then, a couple of additional articles have appeared here that added new information and insight into the technical aspects of such a conversion. During this time, we've learned that the biggest hurdle to overcome during an EFI-MFI conversion has been maintaining proper control of the 4L80-E automatic transmission. This article takes this discussion a step farther, in that it offers a clean and relatively simple solution to effectively maintain control of the 4L80-E.

  36. Throttle Position Switch
    4L80-E Shift Calibration

    The ubiquitous 4L80-E Throttle Position Switch first appeared as part of the GM diesel powertrain in 1991 with the introduction of the then brand new 4L80-E electronically-controlled 4-speed automatic overdrive transmission. Whether either for gas or diesel application, a TPS relayed throttle position information to the transmission control module (TCM), which allowed the TCM to control shift scheduling and shift quality. At the same time, GM designed a new TPS that bolted onto the passenger side of the DB2 fuel injection pump, making for an easy installation. Go here to learn how to adjust the TPS to allow correct 4L80-E shift calibration.

  37. TurboMaster
    Mechanical Turbo Wastegate Actuator

    With a GCVW of more than 20,000 lbs while towing, power is an issue I think about. The new TurboMaster wastegate actuator goes a long way to improve power for the 1992-93 6.5L Turbo Diesels. The TurboMaster is a mechanical wastegate actuator, which can be installed on any of the factory GM 6.5L turbochargers produced between 1992 and 2000. A mechanical actuator is required when converting to mechanical fuel injection. We'll show you how to both install the TurboMaster and adjust it for optimum boost pressure control.

  38. Cruise Control Interfacing
    Retrofit, Troubleshooting & Repair

    Since the late 1980's, GM has used a firewall-mounted electronic cruise control module that remained more or less unchanged through 1999. The 6.2L/6.5L diesels used this cruise control module in the 1988-1993 model-year 6.2/6.5 diesel (mechanical fuel injection) equipped GMT-400 trucks and in the gasoline engine equipped C/K trucks & SUV's through the 1999 model year. Millions of these cruise control modules exist, and knowing how to retrofit a gas module into a diesel application can save you a ton of money if you're having a problem with the one you have now. In addition, these cruise control modules can be used when converting an electronically fuel injected 6.5 to mechanical fuel injection. If you fit into either category, or if you need to troubleshoot your existing cruise control system, this article is for you.

  39. 1992-93 6.5TD
    Hi-Capacity Cooling Mods

    We covered this topic in early 1999, but did not provide much detail about the dual thermostat housing and throttle bracket modifications. This time, we'll focus directly on making the new throttle bracket and show how to modify the new dual thermostat housing. This cooling system modification is necessary when installing GM's factory hi-capacity 130-gpm water pump and dual thermostats on a mechanically injected 6.5L diesel.

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