After observing many occurrences of the on-engine fuel filters “dropping” off of the filter head on Cummins Marine QSB 6.7 and B4.5 engines, Cummins issued a Technical Service Bulletin (TSB) TSB240112 that both shows how to assess the issue and which parts to replace to mitigate the root cause.
Root Cause:
The main cause of this particular failure is that the original threaded insert (or filter head adapter) PN 5443767 Cummins used to attach the on-engine fuel filter to the filter head did not have enough threads to allow the proper torque required to keep the filter in place properly. As a result, the fuel filter loses torque and backs off the fuel filter head due to inadequate thread engagement between the fuel filter adapter and fuel filter.
Resolution:
- Remove fuel filter (Spin-On Type). See corresponding Service Manual. Reference Procedure 006-015 in Section 6.
- Remove and replace the fuel filter head adapter with the new part number in Table 1. See corresponding Service Manual. Reference Procedure 006-017 in Section 6.
- Discard original fuel filter head adapter.
Figure 1: The difference in threads between the old and replacement filter head adapters.
Replacement Parts:
| Part Description | Existing Part Number | Obsolete | Superseded | New Part Number |
| Adapter, Filter Head | 5443767 | No | Yes | 6541589 |
