154406-6400 ZEXEL 9 421 611 200 BOSCH BLEEDER SCREW 9421611200 1544066400 1157292720

Caterpillar: Confidential Yellow
PSP FOR REPLACING UNIT INJECTOR RETURN SPRINGS ON CERTAIN D11N TRACTORS; 776B TRACTORS; 777B, 785, 789 TRUCKS; 3508, 3512, 351 6 ENGINES - PS4591 - MAILED US AND CANADA, CACO, COFA, CFEL, COSA, MARINE TEPS
  The information supplied in this service letter may not be valid after the termination date of this program.   Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.
May 30, 1991 U-110 A-78 AU-66 E-69 O-82 TM-9 PRODUCT SUPPORT PROGRAM FOR REPLACING UNIT INJECTOR RETURN SPRINGS ON CERTAIN D11N TRACTORS; 776B TRACTORS; 777B, 785, AND 789 TRUCKS; AND 3508, 3512, AND 3516 ENGINES. 1290 PS4591 This Program can be administered either before or after a failure. In either case the decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS4591" as Part Number, "7755" as Group Number, and "96" as Description Code. Although this Program is to be administered as described above on the Affected Product, parts stock should be reworked as soon as possible. Termination Date
May 31, 1992
Problem
The return springs for Type 2 unit injectors on certain D11N Tractors; 776B Tractors; 777B, 785, and 789 Trucks; and 3508, 3512, and 3516 Engines may fail in some applications. Type 2 injectors are described on