12v Cummins Killer Dowel Pin (KDP)

KDP Information, Affected Model Years, & Prevention

The "Killer Dowel Pin", as it is so infamously named, refers to a small metal dowel inserted into the engine block that is used to align the front gear housing during initial assembly. It is located above the camshaft gear and to the left (looking at the front of the engine) of the injection pump gear. The KDP is amply named because it can have catastrophic consequences if it dislodges and descends down the front cover. While this pin is found on 12v (6BT) and 24v (ISB) 5.9L Cummins engines, problems associated with dislodging are limited to 12v engines found in 1989 to 1998 model year trucks, and, for inconclusive reasons, most prolific on 1994 to 1998 model year trucks.

Cracked camshaft gears and/or cracked gear housings are amongst the most common failure points when a KDP becomes dislodged and begins dancing around the complex system of gears keeping the engine running in sync. The best scenario following a KDP event is that the dowel pin gently falls to the bottom of the front cover, eventually settling [peacefully] at the bottom of the oil pan where it can rest indefinitely without concern (a screen on the oil pump eliminates the possibility of damage occurring should the pin find its way into the oil pan). The worst case scenario is that the dowel pin becomes lodged between the camshaft and injection pump gears, causing a chain reaction of destruction that includes the pistons meeting the valvetrain and ultimately a catastrophic, unrepairable engine failure.

While affecting all 12v engines, Killer Dowel Pin failures are most common on 1994 to 1998 model year trucks, which utilize the Bosch P1700 injection pump. The [more desirable] P-pump engines are thought to experience different harmonics in the gear train and front cover assembly than 1989 to 1993 engines equipped with the VE44 rotary injection pump. Due to the potentially hazardous nature of the KDP, we highly recommend installing a KDP prevention tab on all 12v engines to permanently eliminate any and all concerns.

KDP Tab/Eliminator Kit Information

A KDP prevention kit is relatively inexpensive insurance against the possibility of a premature, catastrophic engine failure. They work by installing a small metal tab over the dowel pin using an adjacent bolt that secures the gear housing to the engine block. Installation of the tab is simple, straight forward, and intuitive. However it requires removal of the front cover, a relatively invasive and time consuming process for first timers. In reality, the procedures are much more intimidating than they are difficult and a comprehensive installation guide is available at CumminsHub.com. Some KDP kits include a replacement front cover gasket, while more affordable solutions reseal the front cover using RTV silicon. There is some evidence to suggest that using RTV silicon is advantageous to the factory replacement gasket and may provide a more resilient seal in certain instances.

For 1994 - 1998 model year Dodge Rams equipped with the 12v Cummins, we highly recommend the following the kit: 5.9L 12v Cummins KDP Tab & Complete Installation Kit

If you prefer to piece the project together yourself, see the parts list below.

KDP Tab Installation Parts List

Part Description

Part Number(s)

Remarks

KDP tab

Cummins 3958017

OEM option from Cummins. They've recognized the problems associated with dowel pin dislodging and this is their response. There are many alternatives available.

KDP tab bolt

M8 x 1.25 pitch, 25 mm length

Bolt may or may not need to be replaced. Thick KDP tabs often require a longer bolt to reach full thread depth. Available at any decent hardware store. A grade 9.8 bolt is required.

Replacement dowel pin

Cummins 3900257

If your dowel pin is missing, the consensus is that it should be replaced. Available through a Cummins parts dealer.

Front cover crankshaft seal

Cummins 3802820

Works for all 12v Cummins in 1st and 2nd Gen trucks. There are many aftermarket alternatives, some of which fit better than others. The crankshaft seal should be replaced anytime the front cover is removed.

Front cover gasket, 1989 - 1993

Cummins 3914385

Not necessary if sealing with RTV silicon (recommend Permatex Ultra Black). Some experts believe RTV silicon may actually provide a more reliable seal than the factory gaskets. We've found that it is simply a matter of preference and have used both sealant and gaskets without problem. Using RTV silicon trims the cost considerably.

Front cover gasket, 1994 - 1998

Cummins 3918673

Threadlocker

Loctite 271 (or comparable)

Loctite is the leading brand in threadlocker products, but any high strength threadlocker will suffice.

KDP dowel pin location on 12v Cummins diesel

Killer dowel pin (KPD) location identified by arrow.
With the front cover removed from the engine, the KDP is easily accessible.

Closeup view of dowel pin (KDP) on 5.9L Cummins diesel

Close up of alignment dowel. The adjacent bolt is removed and used to secure the KDP tab.

5.9L Cummins 12v diesel with KDP tab installed, preventing dowel pin dislodging

KDP tab installed, permanently preventing the alignment dowel from dislodging.