Thursday, November 03, 2005


We have several Cummins diesel engines in our school bus fleet, the most common being the 'C' model. This diesel is an in-line 6 with an 8.3 litre displacement.
They have been a very reliable engine with only minor problems like oil leaks and the odd head gasket failure.
Our newer buses have the ISC Cummins engines, an electronic version of the older 'C' models. The main reason for going electronic is to control emmissions. Software and a laptop computer is required to analyze the ISC.

Cummins 'C' model diesel engines use a BOSCH inline fuel injection pump. A common fault is oil leaking out the shutdown shaft seal but on this engine a major failure occurred. The mainshaft broke in the pump causing a definite no run condition. This type of failure is a 'first' for our fleet.

The first step is to remove the front plug, allowing access to the injection pump accessory drive gear retaining nut.

Remove the retaining nut with an impact gun and 15/16 impact socket.

Using a suitable puller, remove the injection pump drive gear. The shaft is tapered so there will be a sudden release of the gear from the shaft.

Remove injection lines, fuel supply and return lines, fuel shutdown solenoid, throttle linkage, air/fuel control piping and 4 mounting nuts.

Injection pump is now ready to remove, carefully pull back complete unit & lift out. TIP: The 2 inner mounting nuts between the engine block and pump body are hard to get at, a 15mm 3/8 drive swivel socket and long extension[s] will make removal much easier.

Our shop does not get into major repairs on these injection pumps, we deal with a reputable fuel injection repair shop who have the tools and equipment required to repair and test these units properly.


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