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1998.5-2002 5.9 Cummins 24V

In the late 1990s, as the deadline for meeting stricter emission regulations approached, Cummins developed the 5.9L ISB engine to power all Dodge Ram 2500 and 3500 trucks, beginning in January 1998. The new I6 engine shared some of its hard parts with the late 12-valve engine, but it debuted a 24-valve cylinder head and replaced the mechanical P-pump with the electronically controlled VP44 injection pump. The result was substantially improved airflow, more precise fueling, improved overall drivability, reduced emissions, and an increase in power.

Despite the reputation of the VP44 for being unreliable, the 5.9L ISB, often referred to as simply the 24-valve, was a workhorse of an engine. When it was introduced midway through the '98 model year, its available 235 horsepower and 460 lb-ft torque rating bested Ford's 7.3L Power Stroke and sat at the top of the torque war heap until Ford launched its Super Duty line for '99. The more powerful and efficient Cummins engine was not without its fair share of issues, including Brazilian-cast "53" blocks that were infamous for cracking, and the killer dowel pin, which could still strike at any time.

In mid-1998, Dodge installed a revised 5.9-liter Cummins engine in 2500 and 3500 pickups. The then-new diesel's head had four valves per cylinder and the aforementioned rotary-electric Bosch VP44 injection pump that controls fueling events using signals sent by the ECM. An electric lift pump was added to the fueling process, but interestingly, mechanical injectors were retained on the engine.

Performance gains were abundant thanks to improved airflow (Holset HX35W turbo) and fueling. With the NV4500 manual gearbox, 24-valve 2nd-Gen Cummins trucks produced 235 horsepower and 460 lb-ft of torque - serious power for the period.

For 2001 and 2002 trucks, a "High Output" version of the 2nd-Gen Cummins engine was offered. Boasting 245 horsepower and a massive 505 lb-ft of torque, the HO powerplant had a slightly higher compression ratio and received little more than a stronger NV5600 six-speed manual transmission to produce the big numbers.

Despite its issues, the 5.9L ISB engine was an important development in the era of electronically controlled diesels. Its improved airflow and more precise fueling made it a powerful and efficient engine that was ahead of its time. Today, it remains a popular choice among diesel enthusiasts and collectors.