SCREW 4645855 - Caterpillar

Illustration 1. Orificed Delivery Valve (ODV)The new governor and fuel injection pump groups have new fuel injection pump assemblies (see Charts 1 and 2). The fuel injection pump assemblies have an orificed delivery valve (ODV), see Illustration 1. The former pump assemblies used either a reverse flow check valve (RFC) or a hat check valve, see Illustrations 2 and 3. The new ODV performs the same functions as the former RFC with fewer parts. They both give protection against continuous fuel flow from the fuel transfer pump to the cylinder caused by a cracked or broken fuel injection nozzle. Both (ODV and RFC) bleed the fuel pressure pulses, that occur between injections, back to the fuel transfer pump. The hat check valve does not provide either of those functions.
Illustration 2. Reverse Flow Check Valve (RFC)
Illustration 3. Hat Check Valve
Illustration 4. Notched nuts used on new fuel lines.The new fuel lines groups contain new fuel lines and new fuel injection nozzles. The new fuel lines have a larger inside diameter of 1.83 mm (.072"), compared to 1.6 mm (.063") for the former fuel lines. See Chart 3 for part numbers of the new fuel lines. The new fuel lines can be identified by the notches on the nuts used in the fuel line assemblies. See Illustration 4.
Fuel enters the new fuel injection nozzle assemblies from the top instead of from the side on the former nozzles. See Illustration 5. The fuel line on the new fuel injection nozzle assembly is formed to go over the top of the rocker shaft of the valve mechanism. This will allow the fuel injection nozzle assemblies to be removed without removing the rocker shafts. The rocker shafts had to be removed to take out the former fuel injection nozzles.
Some naturally aspirated engine arrangements have replaced their former high compression ratio (18.2:1) rod and piston groups with lower compression ratio (16.5:1) rod and piston groups. See Chart 4.
Some naturally aspirated Industrial Engine (90N) arrangements use new governor and fuel injection pump drive groups. The new drive groups have a different timing advance than the former drive groups. See Chart 5.
Adaptable To: These changes are in effect with 3208 Industrial Engines (90N65055 and 3Z3472) and 3208 Generator Set Engines (29A789 and 30A1176). The new individual fuel system components ARE NOT interchangeable with the former individual fuel system components. The new components WHEN USED TOGETHER can be used to replace the former components. See the Charts for component changes required for specific engine arrangements.
Illustration 5. New 4W7011 Fuel Injection Nozzle Assembly.