The Cummins C inline 6 diesel engine is still running around the country and a very popular model. It’s an 8.3 Liter and similar to the 5.9L. The main reason for it’s popularity is the 100% mechanical features in it’s design. There is an air fuel ratio control but no emission controls that started with the 2007 engines. This engine came to our fleet starting in the mid nineties and they performed very well. The only problems we had was head gaskets, oil leaks and the fuel injection pumps.
Bosch Fuel Injection Pump
They ran a Bosch inline fuel injection pump which was mechanically driven with an internal governor controlling the fuel delivery. With most of these pumps the one consistent failure was the oil seal leaking out the throttle shaft. We had one failure that was the main shaft of the pump breaking in two. Other than that they worked well and you could actually adjust this pump which we didn’t do much of and left that to the local injection shop.
Below I have some straight forward steps on how to remove the Bosch fuel injection pump. It’s fairly basic and all you need is a gear puller, combo wrenches, sockets and an impact gun. There are timing pins on the gear case and the injection pump that you engage before removal that will set the engine on #1 TDC.
(NOTE: Remove the retaining nut FIRST before engaging the drive gear timing pin). There is also a timing pin for the injection pump that is located on the outside of the housing. Here is a great video to show you how it’s done.
To gain access to the injection pump drive gear you have to remove the threaded round cover with a good set of water pump pliers or an oil filter wrench depending on how tight it is. This will expose the gear retaining nut.
Using an impact wrench and a 15/16 socket rattle off the retaining nut holding the gear on to the injection pump shaft.
Next use a gear puller (this one is a harmonic balancer puller)and pull the gear off of the pump shaft. When the gear pulls off it will do it suddenly because of the tapered shaft on the injection pump. 
Remove the injection lines, return lines, fuel shutdown solenoid, throttle linkage, air/fuel control piping and 4 retaining nuts at the timing gear housing. 
The pump is ready for removal and just needs some TLC to maneuver it out of the gear housing and surrounding accessories. I found that using a 3/8 drive 15mm swivel socket and extensions work well removing the 2 injection pump retaining nuts at the inside of the block. 
Watch the video first before starting this job so you get an idea how the timing pins work for the drive gear and the injection pump. These have to be in place to mark them both on #1 TDC especially for re-installation. Thanks for reading and feel free to comment below.
