Mechanical Gas Fuel System G5.9, G8.3 – 005-003   Air/Fuel Mixer

WARNING  Natural gas is explosive and flammable. Keep all cigarettes, flames, pilot lights, arcing equipment, and switches out of the work area and areas with shared ventilation to reduce the possibility of severe personal injury or death when working on a natural gas system.

WARNING  Natural gas is lighter than air. Check the ceiling of the area where work is to be done for any possible ignition sources.

WARNING  Always have proper ventilation when working on a natural gas system.

WARNING  Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.

CAUTION  To reduce the possibility of shock loading of components downstream of the supply valve, opening and closing of the gas supply valve must be done slowly.

• Disconnect the battery cables.
  Refer to Procedure 013-009 (Battery Cables and Connections in Section 13.
• Slowly close the manual gas supply valve.
  Refer to Procedure 006-063 (Fuel Filter, NG) in Section 6.

Remove the fuel supply line connecting the fuel regulator to the air/fuel mixer power valve.

NOTE: The illustration shows the KTA19GC engine. Although different, the procedure remains the same. Depending on the installation instructions for the site, hard piping can be used instead of hose connections.

Remove the following capscrews:

• Compressor inlet tube to the air/fuel mixer power valve (7/16 capscrews).
• Air/fuel mixer to the air/fuel mixer power valve (7/16 capscrews).
• Air/fuel mixer to the air cleaner tube (3/8 capscrews).

NOTE: The illustration shows the KTA19GC engine. Depending on the installation instructions for the site, a hose and clamps can be used to connect the air/fuel mixer to the air cleaner tube.

Remove and separate the air/fuel mixer from the air/fuel mixer power valve. Discard the gaskets.

Remove the air body from the air/fuel mixer. Retain the lock washers.

Remove the gas body from the air/fuel mixer. Remove the large o-ring from the bottom.

Loosen the two screws holding the fuel jet cover in place. The screws do
not have to be removed.

Remove the gas jet orifice (1) and sealing o-ring (2) from the gas body.

Remove the air jet (3) from the air body of the air/fuel mixer by gently removing the center screw. Hold the shaft from rotating with one hand. Be careful
not to damage the diaphragm.

Inspect the o-rings for wear and other damage. Replace if damaged.

Install the gas valve onto the shaft in the center of the air body. Keep the shaft from twisting. Tighten the screw.

If the shaft rotates, secure it as follows:

• Remove the four screws attaching the air valve cover.
• Remove the air valve cover and the spring.
• Use a 7/16 socket and extension to keep the shaft from turning while you tighten the gas valve (as in previous step).
• Install the spring (and spacer if applicable).
• Install the air valve cover. Align the vacuum port holes in all three places. Tighten the four screws.

Install the new gas valve into the air valve body (note: shoulder facing up). The shoulder of the valve should be flush with the air valve body surface.

Lubricate the gas jet o-ring with a small amount of clean lubricating engine oil and install it on the gas jet.

Install the gas jet and o-ring onto the gas inlet module.

Attach the mixer module to the gas body. Make sure that they seat firmly together.

Tighten the screws in a diagonal sequence.

Lightly lubricate a new o-ring with clean lubricating engine oil.

Install o-ring around the base of the mixer module.

Attach the air body to the air/fuel mixer. Start all four 5/16 x 7/8 capscrews and tighten.

Place a new sticker indicating the current configuration of the mixer on top of the original sticker.

WARNING  When using solvents, acids, or alkaline materials for cleaning, follow the manufacturer’s recommendations for use. Wear goggles and protective clothing to reduce the possibility of personal injury.

WARNING  Wear appropriate eye and face protection when using compressed air. Flying debris and dirt can cause personal injury.

Use solvent to clean the air/mixer valve. Use a soft bristle brush for heavy deposits.

Dry using compressed air.

Inspect the air/fuel mixer body for any signs of damage.

Inspect the flange areas for cracks or damaged capscrew holes.

Use new gaskets to assemble the air/fuel mixer and the air/fuel mixer power valve using four 7/16 capscrews. Hand tighten
only.

Install the air/fuel mixer onto the engine. Install the following capscrews hand tight:

• Four 7/16 capscrews connecting the compressor inlet tube to the air/fuel mixer power valve.
• Four 3/8 capscrews connecting the air/fuel mixer to the air cleaner tube.

NOTE: Shown is the KTA19GC engine. Depending on the installation instructions for the site, a hose and clamps can be used to connect the air/fuel mixer to the air cleaner tube.

Tighten the capscrews

Install the fuel supply line connecting the fuel regulator to the air/fuel mixer power valve.

NOTE: The illustration shows the KTA19GC engine. Depending on the installation instructions for the site, hard piping can be used instead of hose connections.

WARNING  Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.

CAUTION  To reduce the possibility of shock loading of components downstream of the supply valve, opening and closing of the gas supply valve must be done slowly.

• Slowly open the manual gas supply valve. Refer to Procedure
  006-063.
• Connect the battery cables. Refer to Procedure
  013-009.