6BT (5.9L) Cummins Turbodiesel

5.9L 12v Cummins Turbodiesel Specs, History, & Info

The venerable 6BT Cummins was introduced in 1984 for various agricultural equipment applications by Case. Fast forward to 1989, Chrysler partnered with Cummins to offer the 5.9L Turbodiesel in their 3/4 and 1 ton Dodge pickups. The 12v Cummins quickly became a popular alternative to Dodge's V-8 gas engines, as the diesel generated nearly double the torque at low engine speeds and provided a significant increase in fuel economy, particularly while towing. The 12v Cummins, or 6BT, received an intercooler for the 1991 model year and the P1700 injection pump replaced the VE for the 1994 model year. The 12v Cummins is arguably the most popular of the various engine platforms that would follow as its simplistic nature and respectable performance characteristics are highly desirable. The 6BT was the first, and Dodge remains the only engine manufacturer to offer an inline 6 diesel in the pickup truck segment.

5.9L 12v Cummins History & General Information

Cummins produced the 5.9L 12v Cummins for Ram pickup applications through the 1998 model year, where it was phased out in favor of a more emissions friendly 24 valve platform. The engine's widespread applications include light and medium duty trucks, agricultural equipment, and construction machinery. A long stroke and undersquare bore-to-stroke ratio yield favorable low end performance, producing peak torque at a meager 1,600 rpm. Although the 6BT tips the scales at a hefty 1,100 lbs, its burly cast iron block and cylinder head contributes to the engine's superior reputation with regard to reliability and longevity. Additionally, its inline configuration eases service and repair efforts by providing generous amounts of workspace on either side of the engine block without the spacial restrains inherent of V-8 arrangements.

12v Cummins Heater Grid Cycle Schedule

In place of a traditional glow plug system, the 6BT Cummins relies on a heater grid (single resistive heating element) mounted between the air horn and intake manifold to assist with cold starting. Cummins engines are well known for starting quickly and with minimal effort, despite the fact that the heater grid is only designed to cycle when the ambient temperature drops below 59° F.

Intake Air Temperature

Pre-Heat Cycle Time

Post-Heat Cycle

> 59° F

no pre-heat cycle

no post-heat cycle

59° F to 15° F

~ 10 sec


15° F to 0° F

~ 15 sec


< 0° F

~ 30 sec


As no engine is without inherent faults, the 12v Cummins Achilles heel is a small dowel pin pressed into the front of the engine during assembly to inhibit proper alignment of the front cover (timing cover). Technicians and shade tree mechanics alike have come to coin this the "killer dowel pin". The small dowel is amply named because, should it dislodge, the chances are high that the pin will bind between the series of timing gears in the front cover. The consensus is that engine vibration causes the dowel to pin to slowly work itself out of its bore. In its descent from the top of the front cover (timing gear housing) to the basin, the pin may lodge itself between the timing gears and fatally wound an engine. Multiple manufacturers produce a KDP eliminator kit and although the installation is labor intensive, it's inexpensive insurance against engine failure.

The 12 valve Cummins was offered behind a number of transmissions during its service life, which include the Chrysler 47RH (4 speed automatic), GETRAG G360 (5 speed manual), and New Venture NV4500 (5 speed manual). Of all transmissions offered, the NV4500 5 speed manual transmission is by far the most popular and desirable transmission option. The transmission suffers from 5th gear failure, however this is easily repaired and even preventable. The transmission's reputation is otherwise sound and its ratio spread provides a comfortable driving experience in loaded and unladen driving conditions.

5.9L 12v Cummins Specs

Production Years:

1989 - 1998


Inline 6 cylinder

B50 Life:

350,000 miles (~560,000 km)


359 cubic inches, 5.9 liters

Bore x Stroke:

4.02" x 4.72"

Cylinder Head Material:

Cast iron

Engine Block Material:

Cast iron

Firing Order:


Compression Ratio:

17.0 : 1


Direct Injection (DI), mechanical injection pump, mechanical fuel injectors

1989 - 1993

Bosch VE44 rotary injection pump

1994 - 1998

Bosch P7100 injection pump


1989 - 1991 MY

Holset H1C turbocharger, non-intercooled

Mid 1991 - 1993 MY

Holset H1C turbocharger, air-to-air intercooler

1994 MY

Holset WH1C turbocharger, air-to-air intercooler (note - 1994 engines will either use a WH1C or HX35)

1994 - 1998 MY

Holset HX35 turbocharger, air-to-air intercooler


OHV, 2 valves per cylinder, solid lifter camshaft

Valve Lash (Clearance):

Exhaust Valve:

0.020" (engine cold)

Intake Valve:

0.010" (engine cold)


Approx. 1,100 lbs dry

Oil Capacity:

12 qts w/ filter

Governed Speed:

2,700 rpm


160 - 215 HP @ 2,500 rpm


400 - 440 lb-ft @ 1,600 rpm

Engine Dimensions:







12v Cummins Horsepower & Torque by Model Year

Note - power ratings only applicable to Dodge pickup applications.

Model Year



1989 - 1993

160 hp @ 2,500 rpm

400 lb-ft @ 1,600 rpm

1994 - 1995

• 160 hp @ 2,500 rpm (auto trans)
• 175 hp @ 2,600 rpm (manual trans)

• 400 lb-ft @ 1,500 rpm (auto trans)
• 420 lb-ft @ 1,500 rpm (manual trans)

1996 - 1998

• 180 hp @ 2,500 rpm (auto trans)
• 215 hp @ 2,600 rpm (manual trans)

• 420 lb-ft @ 1,500 rpm (auto trans)
• 440 lb-ft @ 1,500 rpm (manual trans)

12v Cummins Horsepower/Torque vs Model Year Graph

6BT Cummins factory horsepower & torque ratings by model year