6.5L GM/Detroit Diesel

6.5L Diesel Specs, History, & Information

The GM/Detroit 6.5L diesel was rolled out for the 1992 model year and offered alongside the 6.2L, which would be retired after the 1993 model year. At this point, the diesel marketplace was headed in such a direction that the truck/engine combination that could work the hardest while using the least amount of fuel would reign supreme. Ford was dominating in sales, and the 6.2L wasn't attracting the attention that Ford's IDI and Dodge's Cummins powered pickups were. The result was a new engine, roughly based on the 6.2L, that would supplement what the 6.2L was known for while boosting performance significantly to prove that GMC and Chevrolet pickups could run with the herd.

GM's government contracts continued, and though 2000 was the final model year of the 6.5L for GMC and Chevy, engine production continued through Humvee manufacturer AM General under license from General Motors. The 6.2L and 6.5L diesels are dimensionally similar, and thus most exterior bolt-on components are interchangeable between the two engines. Like its predecessor, the 6.5L bellhousing bolt pattern and engine mounts are identical to those of GM V-8 gasoline engines.

 

6.5L GM Diesel Specs

Manufacturer:

Detroit Diesel (a division of GM at the time)

Production Years:

1992-2000; currently still used in military applications, produced by AM General

Applications:

Chevrolet/GMC: Tahoe, Yukon, Suburban, C/K pickups, 2500 & 3500 trucks.
AM General: Hummer & HMMWV

Configuration:

V-8

Block/Head Material:

Cast iron block, cast iron heads

Displacement:

395 cubic inches, 6.5 liters

Compression:

18:1 - 21.3:1 depending on year & application

Bore:

4.06 inches

Stroke:

3.82 inches

Injection:

IDI (indirect injection), Stanadyne DS-4 injection pump

Aspiration:

Turbocharged & naturally aspirated versions available

Max Engine Speed:

3,400 rpm

Horsepower:

• 180 hp @ 3,400 rpm (introductory)
• 215 hp @ 3,200 rpm (max)

Torque:

• 360 lb-ft @ 1,700 (introductory)
• 440 lb-ft. @ 1,800 rpm (max)

 

The 6.5L Detroit diesel maintained the fuel efficient image that was used to market its predecessor. A variety of applications used the 6.5L, and as such several versions were produced. A special "Fuel Miser" 6.5L surfaced in Chevrolet's P trucks (delivery trucks), for example. Additionally, turbocharged and naturally aspirated versions were made available. Common 6.5L problems include cracks propagating in the main caps and crankshaft failures from aging/fatigue of the harmonic balancer. Overheating issues are also common, and have been known to lead to cracked cylinder heads amongst other failures. The 6.5L diesel was retired to make way for GM/Isuzu's Duramax diesel, launched for the 2001 model year.

 

Variation

Description

L49

Naturally aspirated, standard.

L56

Turbocharged, emissions controlled (EGR & catalytic converters); used in all light duty 1/2 & 3/4 ton trucks

L57

Naturally aspirated

L65

Turbocharged, heavy duty 3/4 & 1 ton trucks.

LQM

175 rated horsepower

LQN

190 rated horsepower

"Fuel Miser"

120 hp, 260 lb-ft. torque, optional in Chevrolet P trucks

 

6.5L Diesel PMD/FSD Failures

PMD failures are arguably the most commonly experienced problem with the 6.5L diesel. The PMD, or Pump Mounted Driver is an electronic module affixed to the side of the injection pump that controls the fuel solenoid. It is also often referred to as the FSD, or Fuel Solenoid Driver. The PMD's fatal flaw is its location on the driver side of the injection pump, which sits in the engine valley. While energized, the PMD generates an intense amount of heat, which does not properly dissipate (do to its location) and ultimately leads to the module's demise. Most hard start, no start, and engine stalling concerns are attributed to a failed or failing PMD. It is extremely common for owners to mount the driver in a remote location and/or install an aftermarket heat sink to a relocated PMD to keep it from overheating. While the PMD/FSD is certainly the 6.5 diesel's Achilles heal, concerns are easily remedied thanks to response from the aftermarket.