1986/10/20 Caterpillar

Orifice Screen Assembly Now Used For The Timing Advance Mechanism{1251,1272,1288,1292}

Usage:

3406B ( 7FB ) Truck Engines

Description of Change: An orifice screen assembly is now used in the fuel injection pump group on 3406B Truck Engines. The orifice screen assembly restricts oil flow to the timing advance mechanism (drive group). The restricted oil flow increases the time required to obtain full advance during acceleration and reduces engine and total vehicle noise levels.

The new orifice screen assembly (Illustration 1) is located in a single tapped hole in the end of the fuel pump camshaft (Illustration 2).

Illustration 1. 7C2568 Orifice Screen Assembly.

Illustration 2. Location of orifice screen assembly for the automatic timing advance unit.

Keep the following points in mind with regard to this new feature:

1. When timing advance operation is checked with the 6V3100 or 8T5300 Engine Timing Indicator Groups, allow additional time (at least 30 seconds) at each rpm test point.

2. Acceptable operation of the timing advance unit (ability to obtain full advance, for example) is more sensitive to any defect that causes increased oil leakage from the advance unit or increased restriction of the oil supply. Check for loose bolts, worn or damaged seals, or a plugged orifice screen if full advance is not obtained.

Adaptable To: The new 7C2568 Orifice Screen Assembly is effective with fuel injection pump Serial Number 66120 (approximately 7FB55250). It is not adaptable to earlier models.

Caterpillar Information System:

1986/10/20 New Oil Pump Relief Valve Guide{1304}

1986/10/13 Remanufactured Final Drive Hubs And Housings (U.S. And Canada){4000,4002,4054}

1986/10/13 Water Level Switch Improved{1354,1350}

1986/10/13 New Piston Oil Ring Gives Better Oil Control{1215}

1986/10/13 New Service Tools Available{0600}

1986/09/29 Improved Damper Guard Used{1205}

1986/09/29 Use Correct Compression Seal Washer (Gas Seal) On 7000 Series Fuel Injection Nozzles{1254,1250}

1986/09/22 Improved V-Belts For Alternator{1405}

1986/09/22 More Flexible Lockwire Used With Nylon Seals For Sealing Critical Areas{1257,1264}

1986/09/22 Longer Adjusting Screw And Jamnut Available For Use In Valve Rocker Arms{1123,1105}

1986/09/22 Windshield Wiper Motor Cross Reference{7305}

1986/09/22 Time Requirement Guides (TRG) Available{0370,0374}

1986/10/20 Caterpillar Crankshaft Heat Code Locations{1202}

1986/10/20 Check Connecting Rods After Engine Failures Involving Hydraulic Lock{1218,1225}

1986/10/27 Check Oil Drain Hole In OR2671 Or OR2621 Remanufactured Cylinder Heads If Head Used With Breather{1100,1300,1317}

1986/10/27 Stronger Oil Level Guide Used{1326,1300}

1986/10/27 New Indicator Instrument Group Available To Measure Crankcase Blowby And Radiator Air Velocity{0781,1200,1350}

1986/11/03 Custom Product Microfiche Library Is Now Part Of U.S. Product Parts Book Library {0374}

1986/11/03 New Jacket Water Heaters Have Longer Thermostat Life {1383,1450}

1986/11/03 High Loads Require Additional Oil Capacity {1318,1214,1215}

1986/11/03 Two New Cold Weather Fuel Heaters Available {1296}

1986/11/03 Nylon Seals Used On Lockwire To Seal Critical Areas; All Subsidiary Dealers Can Now Order Parts Service Seals {1257,1264}

1986/11/10 Caterpillar Antifreeze Now Used And Available From Parts Departments{1350,1395}

1986/11/10 New Fuel Ratio Control Used{1278}