Detroit Diesel — Compensation Adjustment (PGA Hydraulic Governor)
Adjustments · PGA hydraulic governor compensating needle valve
From a Detroit Diesel service manual — check it applies to your exact model before use.
Before you start
- The needle valve must never be closed tight
Procedure
- Loosen the air vent plug far enough to establish a leak; start engine and run at idle speed.
- Open the compensating needle valve several turns to cause the engine to hunt and force trapped air out.
- Allow the engine to hunt at idle until all trapped air is bled (leakage of only oil at the vent screw); tighten vent screw and add oil if necessary.
- Close the compensating needle valve slowly until the hunting condition is minimized or eliminated.
- When operating temperature is reached, open the needle valve again several turns then close slowly until hunting is entirely eliminated.
- Test stability by disturbing engine speed; if hunting starts, close the needle valve slightly and test again.
- Keep the needle valve as far open as possible to prevent sluggishness and still obtain stability.
Specs & values
- needle valve usually open between one-quarter turn and three full turns
- needle valve setting will vary from 1/16 to 2 turns open
Source: Detroit Diesel 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.