Cummins/Onan B43 / B48 — Fuel Pump Repair
Repair & overhaul
For the Cummins/Onan B43 / B48, from the Cummins/Onan service manual.
Applies to: Cummins/Onan B48
Before you start
- A clogged diaphragm air bleed hole can cause diaphragm wear and seal damage.
- Improper fuel pump parts alignment or misconnected fuel lines can result in leaking fuel, creating a serious fire hazard.
Procedure
- Remove the vacuum and fuel lines; inspect the lines for wear, cracking, or brittleness; replace as necessary.
- Scribe a line across the outer pump parts on each end of the pump to insure correct alignment.
- Holding the pump carefully, remove the assembly screws.
- Pull apart the pump sections and check for worn or damaged parts; replace with new parts or install pump repair kit.
- Check and unclog if necessary the small diaphragm air bleed hole located behind the pump diaphragm in the pump base.
- Replace gaskets and reassemble pump.
- Reinstall assembly screws, checking the scribe marks for proper alignment.
- Reinstall fuel and vacuum lines and clamps.
Full service-parts list: Cummins/Onan B48 →
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.