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Old 11-24-2009, 07:20 PM   #3 (permalink)
Green Machine
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#18:1 compression EngineTechnical Discussion on the 18:1 Engine


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A1 Customs - A vendor to be very careful of. Aka, steaksauce.Antilock Braking System (ABS) - Electronically controlled system that senses wheel lockup during braking and relieves hydraulic pressure at wheel which is about to skid.

Acetone - Do not use in your tank!! It easily evaporates at 70deg.

Acronyms- Find out meanings to common acronyms.

Additive(s) - Anything added to crankcase or fuel tank to enhance and preserve operation of the engine system. Additional information available in Fuel Additives

Air Filter Study - Comprehensive study of various air filtersAir In Fuel System -
  • Symptoms of Air In Fuel System: Click Here.
  • Where Are The Likely Locations For Air Leaks: Click Here.
  • How to Test For Air In Fuel System: Click Here.
  • Picture of Clear Return Line Installed: Click Here.
  • How to Find Air Leaks: Click Here
  • How to Pressurize the Fuel System To Check For Air Leaks: Click Here
Air Intakes - see Boost and Filters

Air Conditioning - To understand this system Click Here.

Alternator - Device that generates voltage which provides power to charge batteries and other electrical devices within the vehicle electrical system.
  • Common problems of a bad alternator - Low voltage, batteries not charging, erratic tachometer readings.
  • Alternator upgrade info in DIY section
  • 1996 & 1999 Alternator pulley size = 2-3/8" O.D.: Click Here
  • 1995 Alternator pulley size = 2-5/8" O.D.: Click Here
  • 1994 Alternator pulley size = 2-5/8" O.D. GM spec: Click Here
Alternative Fuel - Any fuel that is not Diesel. SVO, WVO, Bio-Diesel

APP (Accelerator Position Potentiometer) - This acts as a throttle cable through the drive-by-wire system. Commonly known as an APPS (Accelerator Pedal Position Sensor). Failure modes for the APP system are as follows:
  • If only one sensor fails, the vehicle will operate normally. The PCM will store a DTC, but will not illuminate the “Service Throttle Soon” lamp in the instrument cluster.
  • If two sensors fail, the engine will operate at reduced power. The PCM will store a DTC and will illuminate the “Service Throttle Soon” lamp.
  • If all three sensors fail, the PCM will store a DTC and illuminate the “Service Throttle Soon” lamp. The PCM will also reduce engine power to idle.
  • How to tell when it's bad. Click Here


Battery connections - Various problems associated with these. Read this thread, can cause voltage issues, intermittent stalling, studdering, etc.

Battery Manufacturers - Link to a list in this post Here

Battery Terminals - The stock side terminal connections are weak. You can make your battery connections MUCH more stable by doing a simple mod if you want to keep your side terminals.
Black Smoke & GM 6.5 Turbo Diesel INFO - A topic that regularly rears is head here in the 6.5TD forum is “How can I make my 6.5 smoke like crazy?”, or alternately “My 6.5 is pouring out black smoke, how can I make it stop!” For more information Click Here

Block Heater
Blower Motor -
  • How To Test The Blower Motor: Click Here.
  • How To Remove The Blower Motor: Click Here.
  • Adding Ground To Blower Motor: Click Here.
  • How To Replace The Blower Motor Speed Control aka Resistor:Click Here.

Boost Diagnostics - For information regarding this topic see this thread.

Boost Fooler - By using a 10k Pot you can fool the PCM by adjusting what it reads from the MAP Sensor. For more information about this mod Click Here.

Brakes - Device used to slow or stop a vehicle.Brochures - GM Sales Brochures, Commercials & Promo's .

.............. 1992 ............. 1993 ............. 1994 ............. 1995 ............. 1996 ............. 1997 ............. 1998 ............. 1999 ............. 2000 .............

Buying a 6.5L Diesel - Please see Purchasing a 6.5L Diesel.


CDR (Crankcase Depression Regulator) - Similar to a PCV valve on a gas engine. It regulates the amount of vacuum in the engine crankcase to prevent oil leaks. Click here for technical info.

CEL (Check Engine Light) - see MIL

Clutch Troubleshooting - Click here

CODES - There are the two styles of computer "codes" that you will be looking for, Pre 1996 (OBD I) and 1996+ (OBD II).Computer - see PCM

Connecting Rod Bolts - Talk about upgrade to ARP Studs Click Here

Control Arm Bushings - How to on changing 1 ton bushings Click Here

Coolant System - See Engine Cooling

Coolant Crossover Fitting Leak : https://www.dieselplace.com/forum/63...k-connect.html

Cooling Modification - upgrade to a 1997+ cooling system (High output water pump and dual thermostat) with this info. See also engine cooling

CPS (Crankshaft Position Sensor) - PCM reads the CPS module to indicate TDC for each piston, necessary to determine precise timing for the injection pulse. Diagram showing CPS location Here

CPS(Crankshaft Position Sensor) - Removal Tips: Here

Crank Pulley
Cruise Control - sometimes fails with a DTC (engine code/service engine light). Can also not work due to a bad PMD.
  • You can add cruise control to your "non-cruise" truck too, Find out here!

Cylinder Compression_________________


Dash (Bezel) Removal - To remove the Dash Bezel (the piece that goes around steering wheel radio, ac controls, etc) Click Here. That link will also show how to remove the gauge cluster.

Door Repairs - Find out how to complete some door repairs yourself by clicking here.

DTC (Diagnostic Trouble Codes) - see Codes or use the DTC lookup tool

Dyno Runs - Click Here to see members dyno runs.


ECM (Engine Control Module) - The primary computer which controls the Insight's internal combustion engine. In the 6.5 Diesel we use a PCM, see PCM.

ECM Fuse Blowing - -
  • 1994-95: Try disconnecting the Fuel Filter Manager Fuel Heater, then replace the fuse. Fuel heater power is delivered through the ECM circuit. Deteriorating Fuel Heater harness shorts causing the fuse to blow. See picture to locate Fuel Heater harness Here
  • 1996+: Here
ECT Sensor(Engine Coolant Temperature Sensor) - Sensor is mounted in the t-stat crossover manifold, gives PCM accurate temperature input for determination of advance and fuel rates. The Resistance changes at different temperatures with this sensor.
  • ECT chart of resistance values Here
  • ECT location picture Here
  • ECT 'Fooling' for better cold starts: Great mod for Command-Start systems! Look here
  • For a modified version, Look here

EGR (Exhaust Gas Recirculation) - An emission device that recirculates exhaust gases from the engine back into the intake and combustion chambers. This lowers combustion temperatures and reduces NOx. The EGR is a vacuum based system. for information on the vacuum system, See Vacuum System & Pump
  • EGR Valves can be found on vin "S" trucks (1500, 2500LD trucks, 6 lug hubs).
  • EGR Solenoid Wiring Click Here
  • Rough Idle or Rough Acceleration Click Here
  • If you would like to remove the EGR system from your truck you must either block off EGR ports in intake or get a vin "F" intake and install. Then you must get computer reprogrammed to erase the EGR system from computer (Heath Diesel or Kennedy Diesel reflashes), or you may receive codes and trigger the CEL.
  • For EGR Removal Click Here
EGT - Exhaust Gas Temperature

Electricity - Understanding how to interpret your meter when working on the lift pump and OPS Click here.

Engine Cooling: For information about thermostats see Thermostats
Engine Disassembly - Excellent write up on how to tear down a 6.5L engine with pictures Click Here and Click Here

E-PROM or EEPROM - A blue type chip found inside of the ECM on 94/95 6.5L Trucks.

Ether and the 6.5 Check Here

Extended Crank Time - See Hard Starting May be associated with an optical sensor failure on the IP, but not all hard starting is IP related. Cold weather, with a lot of grey/whitish smoke on start up maybe glow plug related. See Glow Plugs for more information. Read up also on fuel supply issues: Lift pump, OPS, fuel line leaks, etc.
Attached Files
File Type: pdf Heaths 6-5 Cooling upgrade.pdf (239.3 KB, 740 views)

Last edited by OkDually; 09-03-2019 at 06:32 PM. Reason: Added CPS removal tips