The timing of the fuel system is according to the camshaft installed in the housing for the fuel injection pumps (15). The difference between the camshafts is in the different angle between the lobes on the camshaft and the slot for the timing pin. The charts give the camshaft for the fuel injection pump and governor group and the timing which the engine has with the camshaft installed.
A. Part number of fuel injection pump and governor group. B. Identification number on housing. C. Location of part number marks on camshaft.
NOTE: Early camshafts had no part number marks on the camshafts. All 4 cylinder camshafts without part number marks at location (C) are 4N4312.
NOTE: If the part number of the fuel injection pump and governor group is not in the chart or if it has a different camshaft, make reference to the parts book, or to TECHNICAL PARTSGRAM; COMMON USAGE IN SLEEVE METERING FUEL SYSTEMS, 4 and 6 PUMP GROUPS, Form No. FEG00707.
The 3306 Engine can have either one of two different camshafts for the fuel injection pump. The 8.5° camshaft is for the 3306 Engines which have a turbocharger, an aftercooler and an automatic timing advance unit. ALL other 3306 INDUSTRIAL AND MARINE ENGINES use the 13.5° camshaft.
The 3304 Engine can have either one of two different camshafts for the fuel injection pump. The 13.5° camshaft is installed in all the later 3304 fuel injection pump and governor groups. It gives better fuel combustion characteristics than the 12.5° camshaft.
Automatic Timing Advance Unit
On some engines, an automatic timing advance unit connects the drive sleeve on the end of the camshaft to the timing gears in the front of the engine. The unit changes the timing of the fuel system according to the engine speed to give better combustion of the fuel at all levels of engine operation. The unit in these engines changes injection timing from 8° 30′ BTC, at 1200 rpm, to 14° 30′ BTC, at 2200 rpm.