Cummins/Onan B43 / B48 — Compression Test
Testing & diagnosis · engine
For the Cummins/Onan B43 / B48, from the Cummins/Onan service manual.
Applies to: Cummins/Onan B48
Procedure
- Run the engine until thoroughly warm.
- Stop engine and remove spark plugs.
- Remove air cleaner and place throttle and choke in the wide open position.
- Insert the compression gauge in one spark plug hole.
- Crank the engine and note the reading.
- Refer to SPECIFICATIONS section for compression pressures.
Tools required
- compression gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Cylinder compression 75 to 115 psi (517 to 793 kPa)
- Pressures are for a warm engine at cranking speed (about 300 rpm)
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.