SEAL-O-RING 4D5256 - Caterpillar

Caterpillar: Confidential Yellow
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.
This Program can only be administered after a failure occurs. The decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS0577" as the Part Number and "7755" as the Group Number. Use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.
This Revised Service Letter replaces the December 22, 1991 Service Letter. A change was made to the Termination Date.
Termination Date
March 31, 1993Problem
Some fuel injectors may fail on certain Challenger 75 Tractors and 3176 Truck Engines.
Affected Product
Model & Identification Number
Challenger 75 (4CJ1-406)
3176 (2YG1-Up; 7LG1-4822)
Parts Needed
Use the following parts in quantities needed to perform repairs. The application of each injector listed is noted. Use remanufactured injectors, unless unavailable.
0R3397 Injector Grp. (4P9510 if reman unavailable for 7LG 250-300 HP)0R3398 Injector Grp. (4P9520 if reman unavailable for 7LG 325 HP and 4CJ)0R3399 Injector Grp. (4P9610 if reman unavailable for 2YG 250-275 HP)0R3400 Injector Grp. (4P9620 if reman unavailable for 2YG 300-325 HP)9X7557 Seal (injector upper O-ring)9X7722 Seal (injector lower O-ring)336044 Seal (injector thrust-pad-retaining O-ring)Action Required
1. Isolate the injector which is causing the problem. Some failure modes require duplication of the conditions where the customer say the problem occurs (i.e. at full load, idle, high speed, low speed, etc.)2. Replace injectors only after verifying a problem using the 1U6661 Unit Injector Tester, cutting out cylinders, etc. Replace any failed injectors according to the rework procedures attached.Service Claim Allowances
This is a 2.5-hour job. Add 0.2 hours for 1st injector diagnostic test and 0.1 hours for each additional injector test. Add 1.2 hours for first injector sleeve replaced and 0.7 hours for each additional sleeve replaced.
3176 Truck Engines
Parts Disposition
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.
Attach. (1-Rework Procedure)Rework Procedure
1. Drain fuel from the cylinder head and fuel manifold. Remove air inlet piping, valve covers and Jake Brake (if equipped) , rocker arm assemblies, and injector hold down bolts. Remove the suspect injector(s) for inspection and test. Mark each injector to denote the cylinder from which it was removed. It is important to install the injector(s) into the same cylinder to prevent combustion gas leaks.2. Test the injector(s) using the 1U6661 Unit Injector Tester. Check for leaks, VOP, and spray pattern. Replace all injectors which do not pass these test.Procedure For Installing The Following Injector Part Numbers:
4P1410, 4P1420, 4P2810, 4P2820, 0R3177, AND 0R3178
1. Inspect the raised edge on the injector cone for signs of damage. If any nicks or dings are present, do not reuse the injector.2. Ream the sleeves before installing the injectors. Ream only until the sleeve has been cut to provide a full length concentric taper past the injector/sleeve sealing interface. Full removal of the indentation created by the cone step edge is