Cummins Diesel 5.9 Liter B Series Engines

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The Cummins Diesel 5.9 liter Engine 6BT, aka the Cummins “12-valve” was the first member of the “B” engine family to be used in a light truck vehicle. The 6BT used Robert Bosch GmbH fuel systems, injector, and VE rotary pump and P7100 inline injection pumps. Some early 6BT’s were supplied with CAV rotary pumps instead, before the Bosch system became the sole standard.Over it’s 10 year life, the 12v went through a number of material changes. First, in 1994 the VE44 injection pump was favorably switched for the P7100. The reliability and power capabilities of the p7100 pump makes it the most desirable pump for your 12v, able to withstand nearly 600rwhp without needing further upgrades. In mid 1991, an air-to-air intercooler was added, reducing engine heat and increasing reliability.Three different turbochargers were used over its lifespan: the Holset H1C, Holset WH1C, and Holset HX35. 

Transmission Options

The 5.9 12v was available with three transmission options:

  • Chrysler 47RH – 4-speed automatic
  • Getrag G360 – 5-speed manual
  • New Venture NV4500 – 5-speed manual

Both of the manual transmissions are capable of handling more power than the 47RH automatic option. The NV4500 manual transmission which was used in later model years is the most desirable of all as it can hold the most additional power without needing internal upgrades. However, it does commonly experience 5th gear failure, although it is a relatively simple repair.

Cummins 5.9L 12v 6BT Engine Specs

Production Years1989-1998
Engine TypeInline-6 Cylinder
Displacement5.9L, 359 cu. in.
Bore x Stroke4.02″ x 4.72″
Cylinder HeadCast iron
Engine BlockCast iron
Firing Order1-5-3-6-2-4
Compression Ratio17.0 to 1
InjectionDirect injected, mechanical injection pump and injectors
1989-1993: Bosch VE44 rotary injection pump
1994-1998: Bosch P7100 injection pump
1989-1991: Holset H1C, not intercooled
1991.5-1993: Holset H1C, air-to-air intercooled
1994: Holset WH1C, air-to-air intercooled
1994-1998: Holset HX35, air-to-air intercooled
ValvetrainOHV, 2 valves per cylinder, solid lifter camshaft
Weight~1,100 lbs.
Oil Capacity12 quarts
Redline2,700 RPMs
Engine Dimensions40″ x 24.9″ x 37.9″

5.9 Cummins Horsepower & Torque By Year

1989-1993160hp @ 2,500rpms400 lb-ft @ 1,600 rpms
1994-1995160hp @ 2,500rpms (auto)
175hp @ 2,600rpms (manual)
400 lb-ft @ 1,500rpms (auto)
420 lb-ft @ 1,500rpms (manual)
1996-1998180hp @ 2,500rpms (auto)
215hp @ 2,600rpms (manual)
420 lb-ft @ 1,500rpms (auto)
440 lb-ft @ 1,500rpms (manual)

12v Common Problems

You can read our full, in-depth common problems guide here. Here is a summary of the common problems associated with the 5.9 Cummins 12v 6BT:

  • Killer Dowel Pin: the dowel pin sitting on the front of the engine can loosen and fall out of its hole leading to catastrophic engine failure
  • Heater Grid Failure: the heater grid is prone to clogging up and failing, resulting in hard starts, no starts, or the engine dying will idling
  • TPS Failure: the throttle position sensor fails over time after accumulation of dust, dirt, water, etc. which can cause erratic engine speeds and poor performance
  • P7100 Overflow Valve: the P7100 injection pump’s spring becomes less effective or the seat erodes causing leaks and poor fuel pressure which leads to misfires, rough idling, loss of power, and hard starting

Cummins Diesel B Series Engines : Operation and Maintenance ›

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