Generac 004373-1, 004626-0 Coolant, Emissions Control System, AIR Fuel Ratio Controller

Section 1 — General Information

Guardian Liquid-cooled 40 kW Generator

1.9ENGINE OIL RECOMMENDATIONS

The unit has been filled with 15W-40 engine oil at the factory. Use a high-quality detergent oil classified “For Service CC, SD, SE or SF.” Detergent oils keep the engine cleaner and reduce carbon deposits. Use oil hav- ing the following SAE viscosity rating, based on the ambient temperature range anticipated before the next oil change:

Temperature	Oil Grade(Recommended)
Above 80º F (27º C)	SAE 30W or 15W-40
32º to 80º F (-1º C to 27º C)	SAE 20W-20 or 15W-40
Below 32º F (0º C)	SAE 10W or 15W-40

Any attempt to crank or start the engine before it

!has been properly serviced with the recommended oil may result in an engine failure.

1.10 COOLANT

Use a mixture of half low silicate, ethylene glycol base antifreeze and half soft water. Use only soft water and only low silicate antifreeze. If desired, add a high qual- ity rust inhibitor to the recommended coolant mixture. When adding coolant, always add the recommended 50- 50 mixture.

Do not remove the radiator pressure cap while the engine is hot or serious burns from boiling liquid or steam could result.

Ethylene glycol base antifreeze is poisonous. Do not use mouth to siphon coolant from the radiator, recov- ery bottle or any container. Wash hands thoroughly after handling. Never store used antifreeze in an open container because animals are atracted to the smell and taste of antifreeze even though it is poison- ous to them.

Do not use any chromate base rust inhibitor with eth- ylene glycol base antifreeze, or chromium hydroxide (“green slime”) will form and cause overheating. Engines that have been operated with a chromate base rust inhibitor must be chemically cleaned before adding ethylene glycol base antifreeze. Using any high silicate antifreeze boosters or additives also will cause overheating. Generac also

recommends that any soluble oil inhibitor NOT be used for this equipment.

1.11 EMISSIONS CONTROL SYSTEM

(Model 004626-0)

This model is equipped with an active exhaust emis- sions control system to comply with certain California air district regulations for natural gas emergency gener- ating sets, including the South Coast Air Quality Management District. Do not tamper with or disable any part of this system, including the exhaust catalyst,

carburetor, oxygen sensor, air-fuel ratio controller, sole- noid valve and gas regulator. These items are not sub- ject to periodic maintenance or adjustment.

This model is of a size (greater than 50 brakehorse- power) that may require a review by air permitting authorities prior to installation and operation. Consult the local air management district for details and specif- ic requirements.

Figure 1.3 - Emissions Control System

AIR FUEL RATIO CONTROLLER

The air fuel ratio controller is an advanced micro- processor designed to work with a three-way catalyst and a feedback (rich bias) carburetor to provide close- loop fuel management. Its digital adaptive control is able to compensate for variations in fuel mixtures and engine tunes. It is time based activated. (For example, it will activate after 45 seconds from receiving the power signal.) The part number for the air fuel ratio controller is 0D4221.

Principle of Operation: The oxygen sensor, installed on the exhaust pipe, between the engine and the catalytic muffler (closer to the engine), continuously monitors the exhaust gas composition. A feedback signal is sent from the oxygen sensor to the air fuel ratio controller, which controls the fuel system to maintain the optimal, stoichiometric air fuel ratio. The air fuel mixture to the engine is controlled by biasing the diaphragm in the fuel regulator using vacuum (from the carburetor). This vacuum signal is directed to the fuel regulator via the control valve. The air fuel ratio controller determines the amount of vacuum signal sent to the fuel regulator. The more vacuum sent to the regulator, the more restricted the fuel flow will be, therefore the leaner the air fuel mixture.

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