6.5 Diesel Technical Library

[knkreb]

Welcome aboard! Housed here is a growing list of information compiled by our members of technical resources for the love and care of your 6.2/6.5L GM Diesel. These engines have reputation. We are unleashing the database of how-to and why's of what you can do to keep your engine up and running it's best.

You can find the names of your parts by consulting the exploded parts diagrams found here. Pick your vehicle, year, model, and voila! Very cool!

Now that you know what it's called, look deeper about what the members have posted about those parts:

A

A1 Customs - a non-site vendor to avoid at all costs. AKA - Steaksauce.

Acetone - Folk lore fuel additive. Don't add it to your tank. It's not compatable with fuel system components.

AMG block here
Info from chrisK1500

Air-To-Air Intercooler (ATA) - A charge air cooler using ambient air to cool the charge air (air compressed by the Turbo, heading to the intake). Charge air passes through the intercooler fins while ambient air is forced over the fins. Much the same way a radiator cools engine coolant, only the engine coolant is replaced by charge air.
Info from RCpullerdude

ATF (Automatic Transmission Fluid) - Belongs in your automatic transmission (Duh). It's another Folk lore fuel additive that some people keep posting will 'clean your injectors, remove deposits, and increase lubricity'. Don't add it to your tank. It doesn't do all those things (although it may have some value in gassers), and can stain the Optic Sensor (OS) in your Injection pump. Same as adding waste oil to your tank... The guys who promote this stuff don't have DS-4 Electronic Injection pumps. We do, and they like fuel without ATF or waste oil... add new 2-stroke or new 30-wt non-detergent oil for lubricity , or approved diesel fuel systems additives.

Autoenginuity - pc-compatible user-friendly software that emulates the Tech2 for OBD2 vehicles - does TDCO LEARN and other functions of the Tech2

B

Battery Connections - This post is a great show-and-tell about a simple, must-do battery post mod that will hlep keep your power flowing!
Info from TurboTahoe

Boost Fooler - A way of convinging the PCM that your boost levels are within range, when really, you are getting close to strecthing the head studs Boost foolers are built by wiring a 10k ohm linear taper potentiometer into the MAP circuit as shown here.

C

CDR - Crankcase Depression Regulator - Similar to a PCV valve on a gasser. It regulates the amount of vacuum in the engine crankcase to prevent oil leaks. In parts store, it is search and listed as PCV (not CDR).

Charge Air - Intake air after going through a turbocharger or supercharger.

Charge Air Cooling (CAC) - Process to cool intake air temp (IAT) in a trubocharged or supercharged engine. Can be an air-to-air or water-to-air intercooler or water methanol injection.
Info from RCpullerdude

Cold Air Inlet mod... here
Info from chrisK1500

Crank Position Sensor - (CPS) - Tells your PCM what your engine geometry looks like, to control injection events. More info here.
Info from chrisK1500


Crankshaft pulley - Aside from being the turning force for your serpentine belt and running all your accessories, the pulley on the front of the engine works together with the harmonic balancer to stabilize the resonance of the rotating assembly. Both of them are rubber-mounted; when the rubber deteriorates, (as shown here), the pulley can disengage from the crank with devestating results (broken crankshaft). Check them often, and replace when needed... this is not a place to cheap-out.
Info from Hydrauk

CTS - Coolant Temperature Sensor - Here is a list of the OHM readings for the sensor at various temps.
Info from chrisK1500

D

Diagnostic Checklist - Filling this out in as much detail as possible helps to collate valuable information when your truck is sick.
Info from JiFaire

Diagnostic Trouble Codes - (DTC) - What do those pesky codes mean? Look here.
Info from Schwind

Reading your DTC Codes (OBD-I only) - How to use a paper clip or jumper wire to read your DTC Codes. Needs your SES light to be working.
Info by JiFaire.

E

E-Prom - Is a blue type chip found inside of the ECM on 94/95 6.5L Turbo Diesel equipped trucks.

ECM Pinouts - Diagrams found here
Info from DnHolland

ECT, engine coolant temperature sensor (aka CTS - coolant temp sensor) CTS
Info from chrisK1500

ESO Engine shut off solenoid. Ign provides 12 volts to the ESO to allow fuel delivery into the DS4. Turning off the Ign cuts off voltage to the ESO. ESO is a 'redundant' switch.
Info from chrisK1500

F

Fan clutch mod - the thermostatic clutch fan on these trucks is famous for engaging too late to do much good... if yours isn't kicking in enough to do the job, you should replace it with a tuned severe-duty fan clutch, but here's a DIY mod that just might work for you... try this one first.
Info from gmctd


Fast Idle Switch Mod - On vehicles equipped with the Electronic DS-4 Injection pumps, hooking up a high-idle modfication is a simple matter. This thread talks about the process for both OBD-I and OBD-II vehicles.
Info from mfgguru

Filter Harness - a small black box found inline from the injestion pump harness to the optical sensor on the injection pump installed on mid 90's DS4 equipped 6.5s. Have been linked to setting codes 17 and 18 if malfunctioning.
Info from chrisK1500

Filter Housing Manager- a round canister (94+) that houses the fuel filter, water in fuel sensor, and fuel heater. Can be modified to a 3/8" outlet (Feed the Beast).
Info from chrisK1500

Fuel Strainer - the little strainer found in the Fuel Filter Manager... many people lose this little guy because it tends to stick to the filter when you change it. If it clogs up, Houston, we have a problem.
This article is by Clipper.

Fuel Supply - "Feed the Beast" modification. This helps to increase fuel supply for peak demand.
This article is by Acesneights1.

FSD (Fuel Solenoid Driver) - See PMD.

G

Glow Plug - Heating element that warms up the air in the precombustion chamber to aid cold starting

Glow Plug Override - a way of jumping the OEM GP relay to get extended glow time...

Here is a quick 'how-to' on installing a manual glow plug override.
Info from chrisK1500

Because Variety and different viewpoints are always handy, Here is another version of installing a manual glow plug override.
Info from Hydrauk


Glow Plug - ECT mod for longer running; use with Bosch Duraterms, AC60g, or other self-regulating plug only. Look here.
Info from chrisK1500

GMTD Scantech - pc-compatible user-friendly software that emulates Tech1 capability for 94 and 95 (OBD I) trucks - does TIMESET and TDCO LEARN and other functions of the Tech1.

Grounds - This thread documents the need for these trucks to have clean, stable grounds at all times... even the Fuse Panels need to be clean!! If you have unexplained codes or gremlins, read this!
Info from TurboTahoe

Grounds - Here is another thread about body, engine, and frame grounds, complete with pics.
Info from ak diesel driver

H

Heater problems... what to do when your blower quits. Look here.
Info from Teroma25

High Idle Mod... see Fast-Idle Mod.


I

Injector Replacement - here
Info from chrisK1500

Intake Air Temp (IAT) - The temp of the intake air going into the engine. Significantly higher in turbocharged and supercharged engines due to the compressed air being warmer.
Info from RCpullerdude

Intercooler install - here
info from Kane on his ATA install


J

K


L


Lift pump - Common failing part located on the frame rail under the driver's seat. How does it work? here Check it's operation to eliminate fuel supply issues. Some failures of the lift pump may even cause engine codes. See also OPS.
Info by knkreb

M

Manuals - Having trouble finding a reference manual, how-to, or wiring diagram? Try looking online at Seneca Library's Auto Repair Reference Centre (ARRC).
Info by BigArt

Modifications - (sometimes called Mods) here is a list of things to consider if you're looking to add to your truck's longevity, reliability, or performance; all of them are good, many are cheap (or free), and you can find more information on each by searching through the technical reference library.
info by Pruittx2

N

O

OBD-I - Computer generation prior to 1996 model year. Computer codes can be checked with a simple paper clip... See DTC for more info
Info by JiFaire.


OBD-II Computer generation 1996 and beyond. Code retrieval requires a code reader. See DTC for more info

Oil Cooler Lines - frequently leak... here's one way to fix them (with pics) Check out this thread
Info by NVW.

Oil Cooler Lines - Complete DIY replacement (with pictures!) with new cooler and lines from Greg at Lubespecialist. Check it out here.
Info by Rodd.

Oil Filter Bypass Kit - Relocate your Oil Filter to a better place!! Complete DIY replacement (with pictures!). Check it out here
Info by Rodd.

Online Reference Manuals - Look under Manuals, above.

OPS - Oil pressure switch - OBD-I systems use the OPS to engage the lift pump. OBD-II systems use both the lift pump and cam signal to engage lift pump. Need to change your OPS? You'll need this tool: Lisle#13250 oil pressure switch socket..
Info by Sunshine

OPS Install - Changing your Oil pressure switch involves getting a little bit intimate with the top of your engine. It's a good idea to put in a relay (to ease the high-amp load on the OPS) while you're in there. This install, complete with pictures, gives you an idea what to expect!
Info by Schwind

Optic Sensor - Supplies the PCM with pump speed, rotor position, cam ring position, and fuel temperature.
Info from chrisK1500

Optic Sensor R/R - Pictorial description of how to change out your Optic Sensor - can become necessary if the old one gets stained or becomes dysunctional. Information from Roy Halvorsen, Norway.

P

PCM - Powertrain Control Module. The 'brain' of the vehicle. Can be reflashed for more economy/performance.
Info from chrisK1500

PMD - Pump mounted driver (aka FSD/fuel solenoid driver)- common failing part. Stock location is on the side of the injection pump. Failure results in stalling. This is not the only cause for stalling.

PMD Extension Cable - DIY: Solder or Crimp? - If you're planning a DIY- extension for relocating your PMD, then you need to read this very informative post before you start.
Info from Radio Man


Q

R

Radio Lights (Changing them) - Have the lights behind your radio buttons stopped working? Here is a pictorial look at how to change them out!
Info from great white


Recalls - Has there been a recall on your vehicle you should know about? Find out by querying this database.

RPO Codes - (Regular Production Options). Codes on your build sheet and located on the RPO label in your glove compartment that describe the factory options that your truck was originally equipped with. Try this handy RPO Lookup Tool
Info from Mad Maxx

S

Serpentine Belt - Multi-V-Groove belt that drives the crankshaft-powered Utilities on the front of the engine... Alternator, Power-steering, Vacuum Pump, Water Pump and Fan. Routing diagram can be found here.
Info from 96 Oilburner

Service bulletins - Has there been a Service Bulletin about your vehicle you should know about? Find out by querying this database.

T

Timing Stepper Motor - (ITS). Motor located on the passenger side of the IP that controls injection timing advance and retard.
Info from chrisK1500

Turbo / Wastegate System ... How does it work? See here
Info by knkreb

Turbo Master (TM) - Is a spring actuated wastegate that sets the boost pressure by adjusting the spring tension. This precision instrument from HeathDiesel controls the Turbo-boost pressure, eliminating the GM Vacuum Wastegate-control system. Often installed when vacuum pump fails or as an owner pulls off the vacuum pump. Can be bought from HeathDiesel for ~$100 or you can make your own version for ~$10-$20.
Info by Green Machine

DIY Turbo Master Step-by-step with pictures... how to build your own!
Info by mfgguru

DIY Turbo Master #2 Step-by-step with pictures... how to build your own!
Info by 625fireman


Turbo - GM8 Rebuild yours, DIY Step-by-step with pictures... See how to do it all here!
Info by Bison

U

V

VIN Stands for Vehicle Information Number, and is the 17-digit serial number found on your vehicle registration (also stamped onto a plate under your windshield in front of the driver, and found on other stickers and plates around your truck)... The VIN carries information about your truck including year, place of manufacture, option codes, and is your link to more information! Common usage includes looking for the 8th digit (a letter) that describes whether your truck is an F (heavy dity), S (light duty), P (Van), etc.

Try this handy VIN decoder!! You can also post your VIN in our Vehicle Information forums (GM, Ford and Dodge) and helpful members will pull the available stored information on your truck including warranty work done, major changes and special order options.
Info by bobbiemartin

W

Warranty - Injection pump warranty is 11 years from date of service or 120,000 miles.

Water Mist Injection (WMI) - A form of intercooling using a fine mist of water into the intake. The water provides a degree of charge air cooling, and is sometimes mixed with methanol. The methanol also adds power as a supplemental fuel.
Info from RCpullerdude

Water-To-Air Intercooler (WTA) - Intercooler using liquid to first cool the charge air, then another, external cooler to cool the liquid. The intercooler itself is a simple device that charge air flows through, and the liquid circulates around the charge air, removing heat from it. The liquid then flows to a radiator-type cooler to transfer the heat to the atmosphere.
Info from RCpullerdude

X

Y

Z

[bison]

For your information,I did extensive research last year about the ofshore 506 blocks on the market today,I went even so far as to import one myself,and in addition to Crisk 1500 reply about fake AMG blocks with no 506 # in the valley,[by the way these blocks have metric 10mm tread in the bellhousing mounting holes,stock is 3/8 std] there are 506 blocks avalable and used by a host of engine rebuilders today that are as far as i can tell identical to genuine AMG blocks,incl 506 and the diamond in the valley, These blocks apear to be avalable only to the guy with the right contacts as i was told by the Chinese sales manager.

[JiFaire]

To build a boost fooler, you need to obtain a 10Kohm linear-taper POT from your local electronics vendor (Radio Shack #271-1715), some wire (16 ga should do) and either a decent crimp-connector set or some rosin-core solder and shrink-wrap.

The POT wires into the 3 wires coming off the Boost sensor, mounted on the intake manifold. (shown in picture #1)



The circuit diagram is shown in picture #2



Once this setup is installed, starting with the POT set to O resistance, you can 'dial-up' the resistance to 'fool' the PCM into seeing less boost than is really there.

To illustrate, your PCM will normally throw an overboost code when your boost is over 10psi sustained... it would first try to reduce the boost, but with a TM installed, that isn't possible, so it woule then defuel in an attempt to lessen the boost and prevent engine damage.

Having a boost fooler in your sensor circuit removes this safety feature and makes it possible to run damaging high boost without the engine being protected.

You should therefore only use this mod with gauges and a level head

[6.5dragracer]

what is a 10K POT??? sorry but im new at this diesel stuff

[matuva]

It's a 10 KiloOhms potentiometer. Available in every radio shack.

[JiFaire]

Here's the IP warranty policy:

[JiFaire]

If you have an OBD-I computer. You don't need a fancy-dan code reader to check your codes, just a paper-clip.

Under your steering column, you have an ALDL plug that looks like this:




With the key off, take a metal paper clip (or another suitable jumper wire) and place the ends in holes A and B. Get a piece of paper and pencil handy, watch the SES light on your dash (beside the speedometer), and turn the key to the ON position. The SES light should start flashing.

flash-(pause)-flash-flash-(long pause) ... that's a code 12. Means there is nothing wrong.

Every code will be repeated 3 times. Write them down as they come up. For instance, you could get:

17-18-35-36-71

That means you have codes 17, 18, 35, 36, and 71

When you're done, and the codes are all written down, clear them by pushing the brake and accelerator pedals to the floor, hold them for 15 seconds, let them up, push them down again, hold, and turn the key off.

Turning the key on again should get you only a repeating code 12 (all is well).

Shut the key off, remove the jumper.

NEVER put the jumper in or take it out with the key on!!

[ocalasales]

Here is a great link for repair manuals, wiring diagrams and specs for ALL Vehicles, I downloaded a complete shop manual for my 95 6.5 Suburban. Best of all it is free.
http://www.senecac.on.ca/library/res...bsco_arrc.html

[JiFaire]

Thank you, Ocalasales! That link is already listed in the Reference library (above) under Manuals, but it never hurts to see a reminder!