Service manual

4. Service 9-2013
No. Description
1 Fasteners
FIGURE 8. GOVERNOR ACTUATOR - FASTENERS
4.5.5 Gas Demand Regulator
Conduct a lock-off pressure test as follows before replacing a demand regulator. Replace the
demand regulator only if lock-off pressure is not within the range of 0.20–0.35 inches (5.1–8.9
mm) WC (Spec A and Canadian GSBB Spec B) or 0.075 ± 0.025 inches (19 ± 6.35 mm) WC
(US GSBB Spec B and Canadian GSBC Spec B).
Lock-Off Pressure Test: Lock-off pressure is determined by pressurizing the back (vent) side
of the regulator diaphragm to simulate gas-air mixer venturi vacuum. Conduct the test as
follows:
1. Connect the regulator inlet to a source of air pressure regulated to 11 inches (28 cm) WC.
2. Disconnect the hose from the engine gas-air mixer at the regulator outlet. The soap bubble
will be placed on the hose barb at the regulator.
3. “T" in two hoses to the end of the regulator vent hose (3/8 inch I. D.). Use one hose to
measure pressure by connecting it to an inclined manometer that reads 0–2 inches (0–50
mm) WC and the other to provide the test pressure.
4. Attach a soap bubble to the hose barb at the regulator outlet. While reading the pressure
indicated by a manometer and watching the soap bubble, blow lightly into the hose being
used to pressurize the regulator. Regulator lock-off pressure is the minimum pressure that
will cause air to flow through the regulator, as indicated by the expanding soap bubble. (At
first the soap bubble may expand due to diaphragm movement but will stop expanding if air
is not flowing through the regulator.)
28 A030A239 (Issue 10)