6.5L GM/Detroit Diesel

6.5L Diesel Specs, History, & Info

The 6.5L Detroit (GM) diesel represents an evolution of the earlier 6.2L. GM began rolling out the 6.5 for the 1992 model year, and it altogether replaced the 6.2 following the 1993 model year. Unlike the earlier engine, the 6.5L was available in both factory turbocharged and naturally aspirated versions, with the turbocharged version offering a healthy increase in performance. The engine is often considered an attractive balance between performance and fuel economy, although it arguably became outdated in the wake of its direct injection competition.

Like the 6.2L, the 6.5L diesel was available in 1/2 through 1 ton pickup models until its retirement following the 2000 model year. However, the engine platform was not retired entirely - Humvee manufacturer AM General continued the 6.5 diesel's legacy under license from General Motors. Unlike the 6.2L, the 6.5L was produced in both naturally aspirated and turbocharger versions, the latter providing significantly more torque.

6.5L GM/Detroit Diesel Specs

Engine:

GM/Detroit 6.5L diesel

Production Years:

1992 to current. Retired from the GMC/Chevrolet pickup line after the 2000 MY.

Displacement:

6.5 liters, 395 cubic inches

Firing Order:

1-8-7-2-6-5-4-3

6.5 diesel cylinder numbers

Engine Block:

Cast iron

Cylinder Heads:

Cast iron

Compression Ratio:

18.1 : 1 to 21.5 : 1 (varied with application, turbocharged vs. naturally aspirated)

Bore:

4.06"

Stroke:

3.82"

Aspiration:

Turbocharged and naturally aspirated versions produced

Injection:

Indirect injection, Stanadyne DS4 injection pump

Valvetrain:

Common overhead valve (OHV), 2 valves per cylinder

Oil Capacity:

7 qts w/ filter for 1992 - 1998 model years, 8 qts w/ filter for 1999+ model years. Always check oil level after filling crankcase.

Engine Weight:

~ 750 lbs

Max Engine Speed:

3,400 rpm

Peak Horsepower:

Introduced at 180 hp @ 3,400 rpm. Offered as high as 215 hp @ 3,200 rpm.

Peak Torque:

Introduced at 360 lb-ft @ 1,700 rpm. Offered as high as 440 lb-ft @ 1,800 rpm.

Many variations of GM's 6.5L diesel were produced, including a special 120 horsepower (260 lb-ft) model specifically for delivery trucks. The most powerful version of the engine used in GMC/Chevrolet trucks was a 215 hp, 440 lb-ft, turbocharged model. For Silverado and Sierra pickups, the engine was backed by either a 4L80E 4 speed automatic transmission (with overdrive) or the popular NV4500 5 speed manual transmission. Common problems with the 6.5 diesel include crankshaft, glow plug, and PMD failure. Overheating is also an issue with the 6.5L, and it can lead to cylinder head cracking. In essence, the 6.5L Detroit diesel was a leap above the 6.2L, but it's generally accepted that the engine was outpaced by Ford's Power Stroke and Dodge's Cummins turbodiesel offerings.

6.5L Pump Mounted Driver (PMD/FSD)

Every engine, regardless of its manufacturer, has an Achilles heel - for the turbocharged 6.5L GM diesel, that is the pump mounted driver. The pump mounted driver (PMD), or alternatively the fuel solenoid driver (FDS, this is typically what Stanadyne refers to it as) is a small module mounted to the driver side of the injection pump. Its purpose is to supply power to the fuel solenoid, which allows or blocks fuel flow to the injection pump. When power is supplied to the fuel solenoid, fuel flows to the injection pump and the engine is allowed to run. When power is cut from the fuel solenoid, fuel flow abruptly stops and the engine will stall.

The problem with the PMD is quite simple; it produces a tremendous amount of heat. While diesel fuel flow into through the injection pump is designed to keep the PMD cool, it neglects to protect the module once an engine is shut down, fuel flow ceases, and a heat soak effect causes the PMD to reach temperatures that the unit is not ideally designed to take. The location of the PMD, the heat it produces, and the lack of heat dissipation also play roles in the life of the PMD. When a PMD becomes faulty or overheats, it may cause the engine to lose power and/or stall. Addition symptoms of a failing PMD include:

• Engine rapidly loses and regains power (can feel similar to a misfire in some instances)
• Engine randomly stalls (stalling is arguable the number 1 sign of a bad PMD)
• Engine will not restart when hot - once cooled, the engine typically restarts normally
• Engine idles rough or experiences poor idle quality
• Engine hard start, no start condition

The symptoms may be experienced to varying degrees, but often only occur when the engine has reached operating temperature. At this point, the injection pump is hot, and the PMD suffers severely in with its poor ability to dissipate heat. The solution to PMD related problems is an aftermarket PMD relocation kit and heat sink. See 6.5L GM Diesel PMD/FSD Diagnostics & Relocation Guide for additional information.