Cummins/Onan — Turbocharger Wastegate Functional (3-04) Checking
Testing & diagnosis
From a Cummins/Onan service manual covering: 4B3.9, 4BT 3.9, 4BTA 3.9, 6B5.9, 6BT 5.9, 6BTA5.9, B3.9, B5.9. Check it applies to your exact model before use.
Applies to: Cummins/Onan 4B3.9, Cummins/Onan 6BTA5.9
Procedure
- Attach a dial indicator so its shaft is in line with the wastegate actuator rod.
- Set the indicator to zero, with no air pressure applied to the wastegate capsule.
- Connect clean regulated air pressure and a pressure gauge to the capsule.
- Apply 200 kPa [29 psi]. The rod should move approximately 5 mm [0.200 in] without sticking or air leakage.
- No air should be heard to leak through a functional wastegate capsule.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 200 kPa [29 psi]
- 5 mm [0.200 in]
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.