How does the 12V Cummins diesel compare to the 24V version? – Jalopnik

Although Dodge diesel trucks haven’t always had Cummins engines, their shared history goes all the way back to 1989, when the inline-six 5.9-liter Cummins diesel first appeared in Dodge trucks. However, the family of 5.9-liter Cummins diesel engines is often divided into four different generations Cummins only separates it into two: the 6BT with 12 valves and two valves per cylinder and the ISB with 24 valves and four valves for each of the six cylinders. After its debut in 1989, the 6BT 12-valve Cummins powered Dodge pickups until mid-1998, when it was replaced by the 24-valve ISB Cummins – and that version lasted until 2007.

The 12-valve Cummins is generally considered to have two generations, with the second generation coming in 1994. Although the second generation 12-valve used many of the same core parts as the first, it featured a number of improvements to the fuel delivery and combustion system. These changes were largely due to the tightening of diesel emissions standards introduced in 1994.

In mid-1998, the first 24-valve ISB generation (or the third generation 5.9 Cummins) was introduced. It featured the manufacturer’s first fuel system with electronic controls, as well as a Bosch-branded VP44 injection pump, designed to meet standards that had become even more restrictive. The last 5.9 Cummins version came in 2003 with a new Bosch CP3 injection pump powering the common rail fuel injection system. More changes took place in mid-2004, including new injectors and a turbocharger with an electronically controlled wastegate – all to regain compliance with emissions standards.

The 12-valve 5.9 Cummins used in the 1989 Dodge Ram produced about 160 horsepower and 400 pound-feet of torque. In 1994 it received upgrades to the injector pump, pistons, intercooler and turbocharger. Available power for manual transmission trucks has been increased to 175 hp and 420 lb-ft of torque. By the end of the 12-valve era, power had increased to 180 hp and 420 lb-ft of torque in models with automatic transmissions and 215 hp and 440 lb-ft of torque when paired with a manual.

While the 12-valve Cummins is one of the best truck engines of all time, the 24-valve Cummins was destined to outperform. When the 24-valve Cummins debuted in mid-1998, it had 215 hp and 420 lb-ft of torque for automatics and 235 hp and 460 lb-ft of torque for manual models. The most powerful 5.9 liter Cummins engines are the last 5.9 24-valve engines produced between mid-2004 and 2007, rated at 325 hp and 610 lb-ft of torque.

As with any engine, there are some 5.9 Cummins years that are best avoided. One of the most notorious problems plaguing a wide range of 5.9 Cummins diesel engines is the deadly dowel pin. At its base is a 5/16-inch steel dowel pin that aligns the aluminum front end with all cast iron 12-valve and 5.9-valve Cummins and 24-valve Cummins engines up to 2002. Unlike other dowel pins used for the alignment, the “killer” pin lives in an open hole that allows it to eventually loosen and drop into the gear drives at the front of the engine. If luck prevails, the dowel pin may fall into the oil pan. Otherwise, it could lodge between the engine housing and the gears, causing massive damage and completely destroying the engine.

Another well-known 5.9 Cummins release revolves around engine block castings known as the “53 blocks” used for 24-valve engines from 1999-2002. These engines, identified by the number 53 molded into the front driver’s side, are more susceptible to cracking than other 5.9 Cummins engines. Once cracked, they leak coolant, eventually requiring a weld repair or a new block. By elimination, the 2003 to 2007 24-valve 5.9 Cummins remains at the top, although the 2003 5.9 is known to suffer from some problems inherent to its newness. It doesn’t hurt that the common rail engines offer decent reliability, on top of their status as the most powerful 5.9 models.