Generac — LP Conversion - Air-cooled standby using 992cc V-Twin engine
Repair & overhaul · Fuel system / demand regulator
From a Generac service manual covering: 4077, 4079, 4109, 4389, 4390, 4456, 4674, 4675. Check it applies to your exact model before use.
Applies to: Generac 4077, Generac 4079, Generac 4109, Generac 4389, Generac 4456
Before you start
- The primary regulator for the propane supply is NOT INCLUDED with the generator.
Procedure
- Turn off the main gas supply.
- Remove the three carburetor fuel hoses from the outlet ports of the demand regulator.
- Disconnect wire #0 and wire #14 from the gas solenoid on top of the demand regulator.
- Remove the demand regulator from the enclosure by rotating counterclockwise.
- Remove the small brass hose fitting from the idle circuit port of the regulator housing.
- Remove the small jet (0D5698A) located in the side of the regulator port on the regulator.
- Refit the brass hose fitting to the idle circuit port using pipe thread sealant.
- Identify both adjustment screws (one accessed from the front, one from the back).
- Reverse procedure steps 1-4 to reinstall the demand regulator.
- To run on LP fuel, turn both adjuster screws 1/4 turn clockwise.
- Make minor adjustments to the preset screw settings to achieve maximum power.
Tools required
- Pipe thread sealant Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- LP fuel pressure to fuel inlet: 11 to 14 inches of water column (0.6 psi)
Full service-parts list: Generac 4077 →, Generac 4079 →, Generac 4109 →, Generac 4389 →, Generac 4456 →
Source: Generac 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.