Generac Power Systems GTH - 990, Owner'S Manual

RECOMMENDED BATTERY

Servicing of the battery is to be performed or supervised by per-

sonnel knowledgeable of batteries and the required precautions. 

Keep unauthorized personal away from batteries.
Use only 12 volt negative (-) ground batteries with a minimum rat-

ing of 450 cold-cranking amps at -17.8C (0 F) (OEM requirements 

may differ).



 Damage will result to the engine starter if 

a battery rated less than 450 cold-cranking 

amps is used.

BATTERY CABLES

Using battery cables that are too long or too small in diameter may 

cause a decrease in voltage which leads to a starting problem due 

to voltage drop. Use a cable size “2” for length up to 10 feet. See 

Figure 1 for battery cable connections.

Figure 1 — Battery Cable Connections

OPERATION AND MAINTENANCE

It is the owner’s/operator's responsibility to perform all safety 

checks; to make sure that all maintenance for safe operation is 

performed promptly; and to have the engine checked by an autho-

rized dealer periodically. Normal maintenance service and replace-

ment of parts are the responsibility of the owner/operator and, 

as such, are not considered defects in materials or workmanship 

within the terms of the warranty. Individual operating habits and 

usage contribute to the need for maintenance service.
Proper maintenance and care of the engine assures a minimum 

number of problems and keeps operating expenses at a minimum. 

See an authorized dealer/distributor for service aids and acces-

sories.

BEFORE STARTING THE ENGINE

Perform the following tasks before trying to start the engine:

Checking and Adding Engine Oil

NOTE:

When adding oil to the engine crankcase, use only high quality 

detergent oil rated with API service classification SJ (or higher) 

SAE 30 weight. Use no special additives.

Select the oil’s viscosity grade according to the expected operating 

temperature. Refer to the chart "Recommended Oil Type" on the 

Page 3. Do not use SAE 10W-40.
Check engine oil level frequently to avoid possible damage from 

running low on oil.
•  Place engine on a level surface.
•  Clean area around oil fill and remove oil fill cap and dipstick. 

(Figures 2 and 3)

•  Wipe dipstick clean. Reinstall and check oil level on dipstick.
• Slowly fill engine with oil through the oil fill opening until it 

reaches the full mark on the dipstick. Stop filling occasionally 

to check oil level. DO NOT OVERFILL.

•  Install dipstick. Install oil fill cap and finger tighten securely.
•  Check engine oil level before starting each time thereafter.

Figure 2 — Oil Check Horizontal Engine

OIL CHECK

Figure 3 — Oil Fill Horizontal Engine

OIL FILL

Adding Fuel

Fill the fuel tank using clean, fresh regular UNLEADED gasoline.

 4 

Battery

Po)

Starter 

Contactor

Typical Battery Ground

General Information