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Generac GT-990 Engine

Name: Generac GT-990 Engine
Brand: Generac

The Generac GT-990 is a 992 L 2-cylinder air-cooled engine rated at 3600 rpm, producing up to 18.6 kW. It powers generator sets from Generac and Power Systems, including the 8.1 GN, Model 004666 and Model 005011. It holds 1.5 L (0.4 gal) of oil.

Also known as: Generac GT-990, GT-990

992.0 L

Displacement

Cylinders

3600 rpm

Rated speed

18 kW

Gross power

On this pageSpecs Generator sets Maintenance FAQ Service intervals Torque & specs Fluids Fault codes Procedures Wiring

Engine specifications

Oil capacity	1.5 L
Displacement	992.0 L
Cylinders	2
Aspiration	Air-cooled
Rated speed	3600 rpm
Gross power	18 kW

Generator sets powered by this engine

Shared across brands: Generac, Power Systems

Generac 8.1 GNGenerac Model 004666Generac Model 005011Power Systems GT-990

How to read your Generac engine serial & model number →

Troubleshooting

Symptoms & remedies

Symptom	Remedy
Generator Produces Zero Voltage or Residual Voltage	TEST 4 - PERFORM FIXED EXCITATION / ROTOR AMP DRAW PERFORM STATOR INSULATION RESISTANCE TEST - SECTION 1.4 PERFORM ROTOR INSULATION RESISTANCE TEST - SECTION 1.4 TEST 7 - TEST STATOR TEST 5 - WIRE CONTINUITY TEST 6 - FIELD BOOST TEST 8 - CHECK ROTOR CIRCUIT REPAIR OR REPLACE FUSES
Generator Produces Low Voltage at No-Load	TEST 11 - CHECK AC OUTPUT FREQUENCY TEST 12 - ADJUST ENGINE GOVERNOR TEST 12A - CHECK STEPPER MOTOR CONTROL TEST 2 - CHECK AC OUTPUT VOLTAGE TEST 13- ADJUST VOLTAGE REGULATOR
Generator Produces High Voltage at No-Load	REPLACE DEFECTIVE VOLTAGE REGULATOR
Voltage and Frequency Drop Excessively When Loads are Applied	TEST 14 - CHECK VOLTAGE AND FREQUENCY UNDER LOAD TEST 79 - CHECK IDLE CONTROL TRANSFORMER TEST 80 - CHECK LC1 & LC2 WIRING TEST 81 - CHECK IDLE CONTROL TRANSFORMER PRIMARY WIRING TEST 15 - CHECK FOR OVERLOAD CONDITION TEST 12 - CHECK AND ADJUST ENGINE GOVERNOR

Fault codes and symptom→remedy steps extracted from this engine’s service/owner documentation; verify against the official manual before servicing.

Common problems

Wiring Error ALARM 2099
Voltage and Frequency Drop Excessively When Loads Are Applied
Fix: TEST 14 - CHECK VOLTAGE AND FREQUENCY UNDER LOAD, BOTH LOW -> TEST 15 - CHECK FOR OVERLOAD CONDITION, NOT OVERLOADED -> GOOD -> IF RECONFIGURED TO LP GAS, VERIFY THAT PROPER PROCEDURE WAS FOLLOWED (REFER TO INSTALLATION MANUAL), GOOD -> OVERLOADED -> DISCONTINUE TESTING, REDUCE LOADS TO UNIT’S RATED CAPACITY, TEST 12 - CHECK STEPPER MOTOR CONTROL, GOOD -> BAD -> REPAIR OR REPLACE, LOOK FOR A SHORTED CONDITION IN A CONNECTED LOAD OR IN ONE OF THE LOAD CIRCUITS, GOOD -> TEST 7 - CHECK STATOR AC POWER WINDINGS, ENGINE CONDITION GOOD -> REPAIR OR REPLACE, BAD -> TEST 16 - CHECK ENGINE CONDITION, GOOD -> GO TO “PROBLEM 18 - ENGINE STARTS HARD AND RUNS ROUGH/LACKS POWER” SECTION 4.3
Utility failure 0
Fix: Crank and start engine, transfer load to Generator if Utility returns above 75% nominal for 15 seconds
Unstable Voltage or Incorrect Output Which is Not Triggering a Shutdown
Fix: TEST 1 - CHECK AC OUTPUT VOLTAGE, ERRATIC -> PROCEED TO PROBLEM 3
Undervoltage 1902
Stepper Overcurrent ALARM 2100
Shutdown Alarm/Fault Occurred Problem 18
RPM Sensor ALARM 1501
Prolonged Over-Voltage Undervoltage 1900
Problem 22 – Battery is Dead Battery is Dead
Fix: Test 45 – Check Battery and Cables
Problem 21 – No Low Speed Exercise No Low Speed Exercise
Problem 20 – Generator Will Not Exercise Generator Will Not Exercise
Fix: Test 45 – Check Battery and Cables
Overspeed ALARM
Cause: Prolonged (60 Hz on a 50 Hz unit, 72Hz on 60Hz unit) Over specified Hz for 3 seconds. Possible cause: Stepper motor/mixer body assembly issue.
Overloaded ALARM 2102
Overload Remove Load ALARM 2399

Compiled from service & troubleshooting documentation across every generator set that uses the Generac GT-990.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter			0C8127		Amazon $18.99 eBay $15.99 FridayParts $21.87
Fuel filter	Generac OE		924-0371	50 hr	Amazon eBay
Oil filter			924-0368	1000 hr	Amazon eBay
Battery	12V, 75Ah		924-0380	600 hr	Amazon eBay
Belt			924-0365	1000 hr	Amazon eBay
Coolant	Generac OE		924-0370	1000 hr	Amazon eBay
Oil	Change the engine oil.	4.31 L	—	150 hr
Spark plug			—	1000 hr

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Repair guides

Step-by-step procedures compiled from the Generac service manual for this engine.

Service intervals

Item	Action	Hours	Months	Notes
Engine oil level	Check	8 hr		Check before each use / at least every 8 hours
Oil and oil filter	Change	8 hr		First service — First 8 hours of operation
Oil level	Check	24 hr	1 mo	Monthly or every 24 hours of continuous operation
Aceite del motor	Change	25 hr		First service — Después del período de asentamiento de 25 horas, se recomienda utilizar el aceite 5W-20 propiedad de Generac para uso continuo.
Oil and filter	Change	25 hr		First service — After first 25 hours of operation
Oil	Change	200 hr	24 mo	First service — First 30 hours (break-in)
Engine oil and filter	Replace	100 hr	12 mo	First service — After first 25 hours; then every 100 hours or 1 year. Cold weather (<4.4°C) or continuous hot (>29.4°C): every 100 hours or 1 year
Aceite de motor y filtro de aceite	Change	200 hr	24 mo	First service — Programa de mantenimiento A
Air Filter	Other	200 hr		Service Air Filter - Every 200 hours or Every Season; clean more often under dusty conditions
Batería (condición, nivel de electrolito y estado de carga)	Check	200 hr	24 mo	Programa de mantenimiento A
Battery condition and charge	Check	200 hr	24 mo	Schedule A maintenance
Engine oil and oil filter	Replace	200 hr	24 mo	First service — Schedule A (Every Two Years or 200 Hours) and Schedule B (Every Four Years or 400 Hours). Change engine oil and filter after first 25 hours. In cold weather (below 40 F / 4.4 C) or continuous hot weather (above 85 F / 29.4 C), change every year or 100 hours.
Huile à moteur et filtre à huile	Change	200 hr	24 mo	First service — Calendrier A: tous les deux ans ou toutes les 200 heures. Changer l'huile et le filtre après les 25 premières heures. En conditions froides (moins de 4,4 °C/40 °F) ou fonctionnant en continu à plus de 29,4 °C/85 °F, changer annuellement ou toutes les 100 heures.
Oil filter	Change	200 hr	24 mo	First service — Every 2 years or 200 hours
Spark Plug	Change	200 hr		Every 200 hours or Every Season
Óleo lubrificante e filtro de óleo	Change	200 hr	24 mo	First service — Trocar após as primeiras 25 horas; Programação A (2 anos ou 200 h); em clima frio (<4,4 °C) ou quente contínuo (>29,4 °C) anualmente ou 100 h
Aceite del motor y filtro de aceite	Replace	400 hr	48 mo	First service — Programa B: cada cuatro años o 400 horas.
Air cleaner	Clean	400 hr		Clean or replace as necessary; R = Replace as Necessary; 400 hours
Air filter	Replace	400 hr	48 mo	Schedule B maintenance
Bougies d'allumage	Clean	400 hr	48 mo	Nettoyer les bougies, vérifier l'écartement ou les remplacer. Calendrier A et Calendrier B.
Bujía(s)	Replace	400 hr	48 mo	Programa B: cada cuatro años o 400 horas.
Bujías	Replace	400 hr	48 mo	Programa B; limpiar, comprobar separación y sustituir
Engine air filter	Replace	400 hr	48 mo	Schedule B. Emissions-critical.
Engine oil and oil filter	Change	400 hr	48 mo	First service — Schedule B (every four years or 400 hours).
Filtre à air du moteur	Replace	400 hr	48 mo	Calendrier B: tous les quatre ans ou toutes les 400 heures.
Filtro de aire del motor	Replace	400 hr	48 mo	Programa de mantenimiento B
Filtro de ar do motor	Replace	400 hr	48 mo	Programação B (4 anos ou 400 h)
Folga da válvula	Adjust	400 hr	48 mo	First service — Inspecionar/ajustar após as primeiras 25 h e depois a cada 400 h; Programação B; exclui 14/18 kW com motor 816 cc
Jeu des soupapes	Adjust	400 hr		First service — Vérifier et régler après les 25 premières heures de fonctionnement, puis toutes les 400 heures.
Luz de válvulas	Adjust	400 hr	48 mo	First service — Programa B; inspeccionar/ajustar cada 400 horas
Sediment trap	Clean	400 hr	48 mo	Schedule B maintenance
Separación de la válvula	Adjust	400 hr	48 mo	First service — Programa B. Inspeccione y ajuste después de las primeras 25 horas y luego cada 400 horas. No necesario en unidades 14/18 kW con motor 816 cc.
Spark plug(s)	Clean	400 hr		Replace every 4 years or 400 hours
Spark plug(s)	Replace	400 hr	48 mo	Schedule B. Emissions-critical.
Spark plugs	Replace	400 hr	48 mo	Every Four Years or 400 Hours (Schedule B); clean, check gap, replace
Valve clearance	Adjust	500 hr	48 mo	First service — Schedule B; inspect/adjust valve clearance after first 25 hours of operation, then at 400 hour intervals. Where applicable; excludes units with hydraulic lifters (14 or 18 kW with 816cc engine).
Vela(s) de ignição	Replace	400 hr	48 mo	Programação B (4 anos ou 400 h)
Air cleaner	Inspect	400 hr	24 mo	Yearly (Y); replace as necessary
Air cleaner	Replace	200 hr	24 mo	Replace as necessary; yearly
Bateria	Check		12 mo	Estado da bateria; todos os anos

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Service specifications

Type	Item	Value	Unit	Condition
Clearance	Valve Clearance	0.002-0.004	inch (0.05-0.1mm)	engine at room temperature 60-80 F
Gap	Folga da vela de ignição	0,020	pol
Gap	Folga da vela de ignição	0,040	pol
Gap	Folga da vela de ignição	0,508	mm
Gap	Folga da vela de ignição	1,02	mm
Gap	Ignition magneto (armature) air gap	0.008-0.012	inch (0.20-0.30 mm)
Gap	Ignition magneto air gap	0.008-0.012 inch (0.20-0.30 mm)	gap	V-twin engines; fixed non-adjustable on single cylinder
Gap	Ignition magneto air gap (V-twin)	0.008-0.012 (0.20-0.30mm)	inch
Gap	Magneto gap between flywheel	0.010	inch
Gap	Magneto gap between flywheel (during replacement)	0.010	inch
Gap	Separación de electrodos de bujía (11 kW)	0.030	in (0.76 mm)
Gap	Separación de electrodos de bujía (16/20/22 kW)	0.040	in (1.02 mm)
Gap	Separación de electrodos de bujía (9 kW)	0.020	in (0.508 mm)
Gap	Separación de las bujías	0.508	mm (0.020 pulg.)
Gap	Separación de las bujías	1.02	mm (0.040 pulg.)
Gap	Spark Plug Gap	0.020	in (0.508 mm)	9 kW (GH-426)
Gap	Spark Plug Gap	0.030	in (0.76 mm)	11 kW (GTH-530)
Gap	Spark Plug Gap	0.040	inch (1.01 mm)
Gap	Spark plug gap	0.50	mm (0.020 inch)
Gap	Spark plug gap	0.508	mm
Gap	Spark plug gap	0.76	mm (0.030 in)	8, 11, and 20kW units
Gap	Spark plug gap	0.76 mm (0.030 inch)	gap	410 cc and 530 cc engines
Gap	Spark plug gap	1.02	mm (0.040 in)	13, 14, 15, 16, 17kW units
Gap	Spark plug gap	1.02 mm (0.040 inch)	gap	990 cc and 999 cc engines
Gap	Spark plug gap (10 kW)	0.020	in (0.508 mm)
Gap	Spark plug gap (11 kW)	0.030	in (0.76 mm)
Gap	Spark plug gap (14-24 kW)	0.040	in (1.02 mm)
Gap	Spark plug gap (16/20/22 kW)	0.040	in (1.02 mm)
Gap	Spark plug gap (410cc 6/7 kW)	0.030	inch
Gap	Spark plug gap (530cc 9/10 kW)	0.030	inch
Gap	Spark plug gap (9 kW)	0.020	in (0.508 mm)
Gap	Spark plug gap (990cc 13/16/18 kW)	0.040	inch
Gap	Écartement des électrodes des bougies d'allumage	0.508	mm (0,020 po)
Gap	Écartement des électrodes des bougies d'allumage	0.76	mm (0,030 po)
Gap	Écartement des électrodes des bougies d'allumage	1.02	mm (0,040 po)
Other	Battery charge output	0.050 to 2.5	amps
Other	Compression Ratio GH-410	8.6:1
Other	Compression Ratio GT-530	9.5:1
Other	Compression Ratio GT-990	9.5:1
Other	Compression Ratio GT-999	9.5:1
Other	Compression difference between cylinders shall not exceed	25	percent
Other	Compression ratio	9.5:1
Other	Exercise time length (16-22 kW)	5	minutes
Other	Exercise time length (9-11 kW)	12	minutes
Other	Fusível do painel de controle	7,5	A
Other	Generator output frequency under full rated load	>58	Hertz	full rated load
Other	Generator output under full rated load	>230	volts	full rated load
Other	Good starter motor maximum	62	Amps	starter performance test
Other	Ordem de partida (10 kW)	15 s de arranque, 7 s de repouso, seguidos por quatro ciclos adicionais de 7 s de arranque e 7 s de repouso		cinco ciclos de manivela
Other	Ordem de partida (14 a 24 kW)	16 s de arranque, 7 s de repouso, 16 s de arranque, 7 s de repouso, seguidos por três ciclos adicionais de 7 s de arranque e 7 s de repouso		cinco ciclos de manivela
Other	Perda de potência do motor por altitude	3,5	% a cada 304,8 m (1.000 pés) acima do nível do mar
Other	Perda de potência do motor por temperatura	1	% a cada 6 °C (10 °F) acima de 15 °C (60 °F)
Other	Rated Horsepower @ 3,600 rpm GH-410	14.8	HP
Other	Rated Horsepower @ 3,600 rpm GT-530	18	HP
Other	Rated Horsepower @ 3,600 rpm GT-990	32	HP
Other	Rated Horsepower @ 3,600 rpm GT-999	36	HP
Other	Redução de classificação GN vs PL	10 a 20	%
Other	Retardo de calentamiento con Arranque inteligente en frío	30	segundos	temperatura ambiente por debajo de la temperatura fijada
Other	Retardo de calentamiento normal	6	segundos	temperatura ambiente en o sobre la temperatura fijada
Other	Starter motor performance, V-twin	Minimum rpm 3250; Maximum Amps 62

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Recommended fluids

Fluid	Grade	Standard	Ambient	Capacity	Notes
Engine oil		API Service Class SJ, SL or better		1.9 Qts	Engine crankcase oil capacity including filter, approximately
Engine oil	10W-30	API SJ, SL or better			Below 40 F and down to 10 F
Engine oil	30 weight organic oil (factory fill)				Units run and tested at factory prior to shipping, no break-in required
Engine oil	5W-20				Aceite 5W-20 propiedad de Generac para uso continuo, después del período de asentamiento de 25 horas.
Engine oil	5W-20 (Generac proprietary)	API Service Class SJ, SL, or better		1.03 L	Oil capacity including filter. Use for continuous use after the 25 hour break-in period; specifically formulated for gaseous powered Generac generators. Do not use special additives. Change every year or 100 hours in cold weather (below 40 F) or continuous hot weather (above 85 F).
Engine oil	5W-30	Aceite orgánico 5W-30 (la unidad se entrega de fábrica llena con este aceite)			Compruebe el nivel de aceite y, de ser necesario, añada la cantidad apropiada con la viscosidad correcta. No llene en exceso. Consulte 'Recomendaciones para el aceite de motor' para tipo/viscosidad.
Engine oil	SAE 10W-30 or SAE 30	API SF or SG		1.5 Qts w/ filter change (1.2 Qts w/o)	Above 40°F
Engine oil	SAE 30 above 32°F; 10W-30 between 40°F and -10°F; Synthetic 5W-30 10°F and below	API Service Class SJ, SL or better; use no special additives		1.5 Qts	Oil capacity including filter
Engine oil	SAE 5W-20/5W-30	API Service class SG, SH, or SJ	below -7°C		Below 20° F (-7° C)
Engine oil	SAE 5W-30 Synthetic	API Service class SG, SH, or SJ			For all seasons
Engine oil	SAE 5W-30 Synthetic (all season)	API Service Class SG, SH or SJ		1.7 Qts	Organic break-in oil is required before using synthetic oil; unit is supplied with break-in oil.
Engine oil	SAE 5W-30 sintético	API SJ, SL o mejor		1.03 l	9 kW; no usar aditivos especiales
Engine oil	SAE 5W-30 synthétique	API classe de service SJ, SL ou supérieure			Huile SAE 5W-30 synthétique pour toutes les plages de température. N'utilisez aucun additif spécial.
Engine oil	Synthetic 5W-20 or 5W-30	API SF or SG		1.5 Qts w/ filter change (1.2 Qts w/o)	Below 40°F
Engine oil	Synthetic 5W-30	API SJ, SL or better			Below 10 F
Engine oil	Synthetic SAE 5W-30	API Service Class SJ, SL, or better			Synthetic SAE 5W-30 for all temperature ranges. Do not use special additives. Capacities incl. filter: approx. 1.1 qt (1.03 L) 9 kW; approx. 1.7 qt (1.6 L) 11 kW; approx. 1.9 qt (1.8 L) 16/20/22 kW.
Engine oil	SAE 10W-30	API Service class SG, SH, or SJ	-7°C to 15°C		20° to 59° F (-7° to 15° C)
Engine oil	SAE 30	API Service class SG, SH, or SJ	above 16°C		Above 60° F (16° C)
Fuel		Gas natural: contenido de BTU de por lo menos 1000 BTU/ft3 (37,26 MJ/m3). Gas LP: por lo menos 2500 BTU/ft3 (93,15 MJ/m3)		250.0 gal (946 l)	Tamaño mínimo del tanque de LP es 250 gal (946 l), salvo que los cálculos de la unidad indiquen uno mayor. Solo sistema de extracción de vapor para LP.
Fuel	Gas natural	mínimo 1000 BTU por pie cúbico (37.26 megajulios por metro cúbico)			Reducciones típicas de gas natural 10-20 % respecto a LP
Fuel	Gaz naturel			37.26 mégajoules par mètre cube (1 000 BTU par pied cube) minimum	Teneur en BTU minimale du gaz naturel.
Fuel	Gaz naturel d'au moins 37,26 mégajoules par mètre cube (1 000 BTU par pied cube)	NFPA 54
Fuel	Gaz propane liquide (gazeux)			93.15 mégajoules par mètre cube (2 500 BTU par pied cube) minimum	Capacité de réservoir de gaz propane liquide minimum recommandée de 946 litres (250 gallons).
Fuel	Gaz propane liquide d'au moins 93,15 mégajoules par mètre cube (2 500 BTU par pied cube)	NFPA 58 / ICC IFGC			Réservoir de gaz propane liquide d'une capacité minimale de 946 litres (250 gallons).
Fuel	LP (vapor)	mínimo 2500 BTU por pie cúbico (93.15 megajulios por metro cúbico)		946.0 l	Se recomienda tanque de LP de 250 gal. (946 l) de tamaño mínimo si se convierte de NG a LP
Fuel	LP Vapor	NFPA 58			Vapor withdrawal only. Recommended Btu content at least 2,520 Btus per cubic foot. Required fuel pressure 0.025 to 0.0305 kg/cm2 (10 to 12 inches water column); must never drop below 0.025 kg/cm2 (10 inches water column)
Fuel	LP gas	At least 2,520 Btus per cubic foot
Fuel	Liquid Propane (LP) Vapor	Btu content at least 2,520 Btus per cubic foot; pressure 10-12 inches water column (0.36-0.43 psi)			Use vapor withdrawal system only
Fuel	Liquid Propane (LP) vapor withdrawal	Minimum 2,520 Btus per cubic foot			Required fuel pressure 10 to 12 inches water column (0.36 to 0.43 psi)
Fuel	Liquid Propane (LP) vapor withdrawn or pipeline Natural Gas				NG min 1000 BTU/cu ft (37.26 MJ/m3); LP min 2500 BTU/cu ft (93.15 MJ/m3); min LP tank size 250 gal (946 L) recommended if converting from NG

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Fault codes

Code	Name	Meaning	Severity	Action
ADVERTENCIA DEL CARGADOR	ADVERTENCIA DEL CARGADOR	Indicador LED amarillo encendido en cualquier estado.	Warning	Comuníquese con un IASD.
AUXILIARY SHUTDOWN	Desligamento auxiliar	A unidade não inicia.	Shutdown	Coloque as chaves de parada auxiliares em FECHADO (I). Apague o alarme.
BAJA PRESIÓN DEL ACEITE	BAJA PRESIÓN DEL ACEITE	La unidad no arranca en AUTO con una pérdida de energía eléctrica.	Shutdown	Revise el nivel de aceite y reponga si es necesario. Si el nivel de aceite es correcto, comuníquese con un IASD.
BAJA VELOCIDAD	BAJA VELOCIDAD	La unidad no arranca en AUTO con una pérdida de energía eléctrica.	Shutdown	Comuníquese con un IASD.
BATERÍA BAJA	BATERÍA BAJA	Indicador LED amarillo encendido en cualquier estado.	Warning	Borre la alarma. Navegue hasta BATTERY MENU del MAIN MENU para revisar la batería. Si indica GOOD, comuníquese con un IASD. Si indica CHECK BATTERY, reemplace la batería.
BATTERY PROBLEM	Problema de batería	Yellow LED illuminated in any state.	Warning	Entre em contato com uma IASD.
Battery Problem	Battery Fault	Battery condition poor or battery charger issue	Warning	Inspect battery condition and connections. Contact IASD if needed.
CARGADOR SIN CA	CARGADOR SIN CA	Indicador LED amarillo encendido en cualquier estado.	Warning	Comuníquese con un IASD.
CHARGER MISSING AC	Charger Missing AC	LED amarelo aceso em qualquer estado.	Warning	Entre em contato com uma IASD.
CHARGER WARNING	Charger Warning	Yellow LED illuminated in any state.	Warning	Entre em contato com uma IASD.
CONTROLLER FAULT	Anomalia no controlador	Falha do controlador.	Shutdown	Entre em contato com uma IASD.
Controller Fault	Control Module Failure	Internal controller fault detected	Shutdown	Contact IASD for assistance
DESCONEXIÓN AUXILIAR	DESCONEXIÓN AUXILIAR	La unidad no arranca.	Shutdown	Coloque los interruptores de desconexión auxiliar en posición CERRADA (I).
DOWNLOAD FAILURE	Falha na importação	Falha de download.	Warning	Verifique o ficheiro e tente novamente.
EMERGENCY STOP	Paragem de emergência	Paragem de emergência ativada.	Shutdown	Entre em contato com uma IASD.
ERROR DE CABLEADO	ERROR DE CABLEADO	La unidad no arranca en AUTO con una pérdida de energía eléctrica.	Shutdown	Comuníquese con un IASD.
EXERCISE SET ERROR	Exercise Set Error	Exercise timer setting error	Warning	Entre em contato com uma IASD.
EXERCISER NOT SET	Exerciser not set	Indicates the exercise timer has not been set.	Info	Set the exercise timer per Section 3.6.
FALLA DE ARRANQUE	FALLA DE ARRANQUE	La unidad no arranca en AUTO con una pérdida de energía eléctrica.	Shutdown	Verifique que la válvula de cierre de la tubería de combustible esté en la posición ON. Borre la alarma. Arranque la unidad en MANUAL. Si no arranca o funciona de forma dificultosa, comuníquese con un IASD.
FIRMWARE ERROR-7	Erro de firmware 7	Erro de firmware.	Shutdown	Entre em contato com uma IASD.
FIRMWARE ERROR-9	Erro de firmware 9	Erro de firmware.	Shutdown	Entre em contato com uma IASD.
FUEL PRESSURE	Fuel Pressure	Fuel pressure warning	Warning
FUSE PROBLEM	Problema de fusible	Unit will not start in AUTO with utility loss. (Firmware 1.11 and older only.)	Warning	Comprobar el fusible de 7.5 A; sustituir con fusible ATO de 7.5 A si está fundido, o contactar un IASD
HIGH TEMP.	High temperature	High temperature switch contacts close if temperature exceeds approximately 140 C (284 F).	Shutdown	Allow unit to cool; generator restarts and LED resets once temperature returns to a safe level.
HIGH TEMPERATURE	Temperatura elevada	Unit shuts down during operation.	Shutdown	Inspecione a ventilação ao redor do gerador, admissão, exaustão e parte traseira. Se não existirem obstruções, entre em contato com uma IASD.
High Temperature	Overheat	Engine operating temperature too high	Shutdown	Inspect ventilation around generator, intake, exhaust, and rear. Ensure no obstructions present.
INSPECCIONE LA BATERÍA	INSPECCIONE LA BATERÍA	Indicador LED amarillo encendido en cualquier estado.	Warning	Inspeccione la batería. Presione ENTER para borrar.
INSPECT BATTERY	Inspect Battery	Yellow LED illuminated in any state.	Warning	Inspect battery; press ENTER to clear.
INTERNAL FAULT	Internal Fault	Internal controller fault	Shutdown	Contact servicing dealer.
LOW BATTERY	Low Battery Alarm	Yellow LED illuminated in any state.	Warning	Desactivar la alarma; comprobar batería en BATTERY MENU; si GOOD contactar un IASD, si CHECK BATTERY sustituir la batería
LOW OIL	Low oil pressure	Low oil pressure switch contacts close when oil pressure drops below the 8 psi range.	Shutdown	Add oil; turn AUTO/OFF/MANUAL switch to OFF and then back to AUTO.
LOW OIL PRESSURE	Pressão de óleo baixa	Unit will not start in AUTO with utility loss.	Shutdown	Verifique o nível de óleo e adicione óleo se necessário. Se o nível estiver correto, entre em contato com uma IASD.
LOW VOLTS REMOVE LOAD	Voltaje bajo, retirar carga	Unit will not start in AUTO with utility loss.	Warning	Desactivar la alarma, retirar cargas domésticas, poner en AUTO y reanudar
Low Battery	Battery Voltage Low	Starting battery voltage below acceptable level	Warning	Inspect battery and battery cables. Charge or replace battery if necessary.
Low Oil Pressure	Low Oil Level or Pressure	Insufficient oil pressure in engine	Shutdown	Check engine oil level and top up if necessary. Contact IASD if problem persists.
MISWIRE	Miswire / Wiring Error	Unit will not start in AUTO with utility loss.	Shutdown	Contactar un IASD
NINGUNA	NINGUNA (LED verde parpadeando)	La unidad funciona en AUTO, pero no energiza la casa.	Info	Revise el MLCB del generador (desconexión del generador). Si está encendido, comuníquese con un IASD.
NO ACTIVADA	NO ACTIVADA	La unidad no arranca en AUTO con una pérdida de energía eléctrica.	Info	Verifique si la pantalla indica que la unidad no está activada. Consulte Activación.
NO UTILITY SENSE	No utility sense	Flashing LEDs indicate utility sense voltage is not connected or is below 168 volts AC.	Info	Verify utility sense voltage connection.
NOT ACTIVATED	Não ativado	Unit will not start in AUTO with utility loss.	Warning	Refer to activation section in owners manual
OVER CRANK	Overcrank	Unit cranks and rests for a preset time limit then stops cranking when it cannot start.	Shutdown	Set AUTO/OFF/MANUAL switch to OFF and back to AUTO to reset the control board.
OVER SPEED	Overspeed	Protection shuts the unit down if it runs faster than the preset limit.	Shutdown	Contact the nearest Authorized Dealer.
OVER VOLTAGE	Over Voltage	Overvoltage alarm	Shutdown	Contact servicing dealer.
OVERCRANK	Overcrank Alarm	Unit will not start in AUTO with utility loss.	Shutdown	Verify fuel line shutoff valve is ON. Clear alarm. Start unit in MANUAL. If it does not start or starts rough, contact IASD.
OVERLOAD REMOVE LOAD	Sobrecarga, retirar carga	Unit shuts down during operation.	Shutdown	Desactivar la alarma, retirar cargas domésticas, poner en AUTO y volver a poner en marcha
OVERLOAD WARNING	Overload Warning	Overload warning	Warning	Remova as cargas domésticas do gerador.
OVERSPEED	Sobrevelocidad	Unit will not start in AUTO with utility loss.	Shutdown	Entre em contato com uma IASD.
OVERVOLTAGE	Tensão excessiva	Unit will not start in AUTO with utility loss.	Shutdown	Entre em contato com uma IASD.
Overcrank	Extended Cranking	Engine failing to start after extended crank attempts	Shutdown	Check fuel supply, spark plugs, and fuel system. Contact IASD for further diagnosis.
Overload	Overload Detected	Electrical load exceeds generator capacity	Shutdown	Remove household electrical loads from generator
Overspeed	RPM Overspeed	Engine running at excessive RPM	Shutdown	Contact IASD for assistance
Overvoltage	Output Voltage High	Generator voltage exceeding nominal rating	Shutdown	Reduce electrical load and restart. Contact IASD if issue persists.
PROBLEMA DE BATERÍA	PROBLEMA DE BATERÍA	Indicador LED amarillo encendido en cualquier estado.	Warning	Comuníquese con un IASD.
PÉRDIDA DE DETECCIÓN DE RPM	PÉRDIDA DE DETECCIÓN DE RPM	La unidad funcionaba, se apagó e intenta reiniciarse, o no arranca en AUTO con una pérdida de energía eléctrica.	Shutdown	Borre la alarma y retire del generador las cargas del hogar. Vuelva a poner en AUTO y reinicie. Si el generador no arranca, comuníquese con un IASD.
RPM SENSE LOSS	RPM Sense Loss Alarm	Unit was running and shuts down, attempts to restart	Shutdown	Desactivar la alarma, retirar cargas, poner en AUTO y reanudar; si no arranca contactar un IASD
RPM Sensor Loss	RPM Signal Loss	RPM sensor signal not detected	Shutdown	Contact IASD for assistance
SERVICE A	Servicio A	Yellow LED illuminated, maintenance due	Warning	Realize a manutenção SERVICE A. Pressione ENTER para apagar.
SERVICE B	Servicio B	Yellow LED illuminated, maintenance due	Warning	Realize a manutenção SERVICE B. Pressione ENTER para apagar.
SERVICIO A	SERVICIO A	Indicador LED amarillo encendido en cualquier estado.	Warning	Realice el mantenimiento SERVICIO A. Presione ENTER para borrar.
SERVICIO B	SERVICIO B	Indicador LED amarillo encendido en cualquier estado.	Warning	Realice el mantenimiento SERVICIO B. Presione ENTER para borrar.
SOBRECARGA. RETIRE LA CARGA	SOBRECARGA	La unidad se apaga durante el funcionamiento.	Shutdown	Borre la alarma y retire del generador las cargas del hogar. Vuelva a poner en AUTO y reinicie.
SOBRECORRIENTE DEL MOTOR DE VELOCIDAD GRADUAL	SOBRECORRIENTE DEL MOTOR DE VELOCIDAD GRADUAL	La unidad no arranca en AUTO con una pérdida de energía eléctrica.	Shutdown	Comuníquese con un IASD.
SOBREVELOCIDAD	SOBREVELOCIDAD	La unidad no arranca en AUTO con una pérdida de energía eléctrica.	Shutdown	Comuníquese con un IASD.
SOBREVOLTAJE	SOBREVOLTAJE	La unidad no arranca en AUTO con una pérdida de energía eléctrica.	Shutdown	Comuníquese con un IASD.
STEPPER OVER CURRENT	Stepper Over Current	Stepper motor over current	Shutdown	Contact servicing dealer.
STEPPER OVERCURRENT	Stepper Overcurrent	Unit will not start in AUTO with utility loss.	Shutdown	Entre em contato com uma IASD.
SUBVOLTAJE	SUBVOLTAJE	La unidad no arranca en AUTO con una pérdida de energía eléctrica.	Shutdown	Comuníquese con un IASD.
TEMPERATURA ALTA	TEMPERATURA ALTA	La unidad se apaga durante el funcionamiento.	Shutdown	Inspeccione la ventilación alrededor del generador, además de las secciones de entrada, escape y trasera. Si no hay obstrucciones, comuníquese con un IASD.
UNDER VOLTAGE	Under Voltage	Undervoltage alarm	Shutdown	Contact servicing dealer.
UNDERSPEED	Underspeed	Unit will not start in AUTO with utility loss.	Shutdown	Entre em contato com uma IASD.
UNDERVOLTAGE	Undervoltage	Unit will not start in AUTO with utility loss.	Shutdown	Entre em contato com uma IASD.
USB WARNING	Aviso de USB	Aviso relacionado ao dispositivo USB.	Warning	Tente novamente com USB de melhor qualidade. Os nomes dos ficheiros no USB não podem ter mais de 8 caracteres.
Underspeed	Engine Speed Too Low	Engine RPM below nominal specification	Shutdown	Contact IASD for assistance
Undervoltage	Output Voltage Low	Generator voltage below nominal rating	Shutdown	Reduce electrical load and restart. Contact IASD if issue persists.
VOLTIOS BAJOS. RETIRE LA CARGA	VOLTIOS BAJOS	La unidad no arranca en AUTO con una pérdida de energía eléctrica.	Shutdown	Borre la alarma y retire del generador las cargas del hogar. Ponga en AUTO y reinicie.
WIRING ERROR	Wiring Error / Miswire	Controller wiring error	Shutdown	Entre em contato com uma IASD.
Wiring Error	Electrical Wiring Fault	Wiring configuration error detected	Shutdown	Contact IASD for assistance

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Procedures

Adjust Valve Clearance adjustment

Tools: Feeler gauge 0.002-0.004 in, 10mm allen wrench

Ensure engine at room temperature (60-80 F)
Remove spark plug wire
Remove four screws attaching valve cover
Rotate flywheel nut to bring piston to TDC of compression stroke
Insert feeler gauge between rocker arm and valve stem; correct clearance 0.002-0.004 inch (0.05-0.1mm)
Loosen rocker jam nut, turn pivot ball stud with 10mm allen wrench while checking clearance
Tighten jam nut to 174 in/lbs torque while holding pivot ball stud; recheck clearance
Install new valve cover gasket and re-attach valve cover
Re-attach spark plug wire
Repeat for other cylinder

Adjusting GT-530/990/999 Valve Clearance adjustment

⚠ Check after first six months of operation

Tools: 10mm allen wrench, feeler gauge, torque wrench

Engine should be cool before checking
Remove spark plug wires and spark plugs
Rotate flywheel nut clockwise to bring piston to TDC of compression stroke
Ensure engine is at 60-80°F
Remove the four screws attaching the valve cover
Loosen rocker jam nut, turn pivot ball stud with 10mm allen wrench while checking clearance with feeler gauge
Set clearance to 0.002-0.004 inch (0.05-0.1mm)
Tighten rocker arm jam nut to 174 in/lbs torque while holding pivot ball stud
Recheck valve clearance
Install new valve cover gasket and re-attach valve cover
Install spark plugs and re-attach wires
Repeat for other cylinder

Adjusting GT-990 Valve Clearance adjustment

Tools: #2 or #3 phillips screwdriver, 10mm allen wrench, feeler gauge

Make sure engine is at room temperature between 60 and 80 F.
Make sure the spark plug(s) are removed.
Remove the four valve cover screws with a #2 or #3 Phillips screwdriver.
Rotate the engine by hand to bring the piston to Top Dead Center of its compression stroke.
Loosen the rocker jam nut.
Turn the pivot ball stud with a 10 mm allen wrench while checking clearance with a feeler gauge.
Hold the pivot ball stud and tighten the rocker arm jam nut; recheck clearance.
Install new valve cover gasket and re-attach valve cover.
Re-attach the spark plug wire.
Repeat the process for the other cylinder.

Adjusting Magneto Flywheel Gap adjustment

⚠ Air gap between ignition magneto and flywheel on single cylinder engines is not adjustable.

Tools: 0.008-0.012 inch thickness gauge

Rotate the flywheel until the magnet is under the module (armature) laminations.
Place a 0.008-0.012 inch (0.20-0.30mm) thickness gauge between flywheel magnet and module laminations.
Loosen the mounting screws and let the magnet pull the magneto down against the thickness gauge.
Tighten both mounting screws.
To remove the thickness gauge, rotate the flywheel.
Repeat the above procedure for the second magneto.

Adjusting Valve Clearance adjustment

⚠ Risk of Burn. Allow the engine to cool before performing the following procedure.

Tools: feeler gauge, 10 mm wrench, 13 mm wrench, 14 mm wrench, 10 mm hex key

Remove spark plug wire(s) and position away from spark plug(s).
Remove spark plug(s).
Remove the four screws attaching valve cover. Remove and discard gasket.
Verify piston is at TDC of its compression stroke (both valves closed).
Loosen rocker jam nut using a 10 mm wrench (10 kW units) or 13 mm wrench (20-24 kW units).
Turn pivot ball stud using a 14 mm wrench (10 kW) or 10 mm hex key (20-24 kW) while checking clearance with a feeler gauge.
Hold pivot ball stud and tighten rocker arm jam nut.
Inspect valve clearance to verify it did not change.
Install new valve cover gasket and valve cover; tighten fasteners in a cross pattern.
Install spark plug(s) and tighten to 18 ft-lbs (25 Nm); attach spark plug wires.
Repeat process for other cylinder if equipped.

Adjusting the Fuel Regulator (Natural Gas Only) adjustment

⚠ Avoid overspeeding the engine.

Tools: Frequency meter

Turn off utility power to the main distribution panel.
Allow the generator to start; confirm no-load frequency (roof open, door off) is 63-63.5 Hz.
Transfer load to emergency circuits and fully load the generator.
Connect a frequency meter to the output lugs of the main line circuit breaker.
Slowly turn the adjustment screws one at a time until the highest frequency is read.
When maximum frequency is reached, turn both adjustment screws 1/4 turn clockwise.
Turn utility power back on and allow the generator to shut down.

Adjusting the Fuel Regulator - 7kW (Natural Gas Only) adjustment

⚠ Do not make any unnecessary adjustments. Factory settings are correct for most applications.

Tools: frequency meter

Start the generator; let it stabilize and warm up at no-load.
Connect a frequency meter across the generator's AC output leads.
Turn the primary adjust screw to obtain a frequency reading.

Ajustar a folga das válvulas adjustment

⚠ Risco de queimaduras. Deixe o motor esfriar antes de executar o procedimento.

Tools: Chave de 10 mm, Chave de 13 mm, Chave de 14 mm, Chave sextavada de 10 mm, Calibrador

Remova os fios das velas de ignição e remova as velas de ignição.
Remova os quatro parafusos que prendem a tampa da válvula; descarte a junta.
Verifique se o pistão está no TDC do seu curso de compressão.
Solte a contraporca do balanceiro (C) com chave de 10 mm ou 13 mm.
Gire o pino de esfera articulada (D) com chave de 14 mm ou sextavada de 10 mm e ajuste a folga.
Aperte a contraporca do braço oscilante e inspecione a folga novamente.
Instale a nova junta e as tampas das válvulas; aperte em padrão transversal.
Instale as velas e aperte a 25 Nm; conecte os fios das velas.

Ajuste de la luz de válvulas adjustment

⚠ Dejar enfriar el motor antes de ajustar.

⚠ Iniciar los cuatro tornillos antes de apretar.

Tools: Calibre de espesores, Llaves de 8/10/13/14 mm, Llave de casquillo, Casquillo grande

Cerrar la válvula de combustible y desconectar la batería.
Retirar cable(s) de bujía y alejarlos.
Retirar la(s) bujía(s).
Llevar el pistón al PMS de la carrera de compresión.
Retirar los cuatro tornillos de la cubierta de válvulas y desechar la junta.
Aflojar la contratuerca del balancín.
Girar el prisionero de bola pivote para ajustar la luz con calibre.
Sostener el prisionero y apretar la contratuerca; verificar y reinstalar con junta nueva.

Ajuste de la separación de la válvula adjustment

⚠ Deje que el motor se enfríe antes del procedimiento.

⚠ Desconecte el cable negativo y luego el positivo de la batería.

⚠ No necesario en unidades 14 o 18 kW con motor de 816 cc.

Tools: Llave de 10 mm, Llave de 13 mm, Llave de 14 mm, Llave hexagonal de 10 mm, Galga de espesores

Retire los hilos de las bujías y las bujías.
Retire los cuatro tornillos de la cubierta de la válvula y deseche la junta.
Verifique que el pistón esté en el PMS de su carrera de compresión.
Suelte la contratuerca del balancín (llave 10 mm en 10 kW, 13 mm en 20 a 24 kW).
Gire el espárrago del pivote (llave 14 mm en 10 kW, hexagonal 10 mm en 20 a 24 kW) ajustando la separación.
Sostenga el espárrago y apriete la contratuerca del balancín.
Inspeccione la separación para verificar que no cambió.
Instale una junta nueva y la cubierta de la válvula; apriete en patrón cruzado.
Instale las bujías y apriete a 25 Nm (18 lb-pie).
Conecte los hilos de las bujías.

Check and Adjust Engine Governor (Single Cylinder Units) adjustment

Tools: frequency meter

Loosen governor clamp bolt.
Hold governor lever at wide open throttle; rotate governor shaft clockwise fully; tighten clamp bolt to 70 inch-pounds.
Start generator and let stabilize at no-load.
Connect frequency meter across AC output leads.
Turn primary adjust screw to obtain 61.5 Hz.
Turn secondary adjust screw to obtain 62.5 Hz.
Check AC voltage; adjust voltage regulator if needed.

Check and Adjust Ignition Magnetos adjustment

⚠ Magneto air gap on single cylinder engines is non-adjustable.

Tools: VOM, thickness gauge 0.008-0.012 inch

Disconnect Wire 18 from terminal by oil cooler.
Disconnect spark plug wires from spark plugs.
Measure primary winding resistance: approximately 300K ±10K ohms.
Measure secondary winding resistance: approximately 14K ±3K ohms.
Check diode isolation between magnetos; INFINITY should be measured.
For V-twin, rotate flywheel until magnet is under laminations.
Place 0.008-0.012 inch thickness gauge between magnet and laminations.
Loosen mounting screws and let magnet pull magneto down against gauge.
Tighten both mounting screws.
Remove gauge by rotating flywheel.
Repeat for second magneto.
Retest for spark.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Voltage reconnection

Voltage	Phase	Connection	Leads	Notes
		0 – c.c. (-)	NOIR no 3	Fil de mise à la terre normal; obligatoire si jumelé à un commutateur de transfert de gestion intelligente de l'alimentation de Generac.
		23	BLANCO Núm. 5	Cable de señal lógica del control de transferencia
		23 (White #5)	E	Transfer Control Signal Wire
		Control system interconnections	N1, N2, 0, 15B, 23	Can be run in same conduit as AC power if length < 35 feet and all wiring rated 600V
		Longueur de fil 1 à 35 m (1 à 115 pi)	Calibre 18 AWG	Conducteurs en cuivre seulement.
		Longueur de fil 35 à 56 m (115 à 185 pi)	Calibre 16 AWG	Conducteurs en cuivre seulement.
		Longueur de fil 56 à 89 m (185 à 295 pi)	Calibre 14 AWG	Conducteurs en cuivre seulement.
		Longueur de fil 89 à 140 m (295 à 460 pi)	Calibre 12 AWG	Conducteurs en cuivre seulement.
		N1, N2, T1, Leads 23 and 194	All conductors rated for minimum 300V	Class 1 remote control/signaling circuits. Install per NEC Article 300 and recognized wiring methods. Sense wires through wire tie C1 to sense wire terminal block B. Control wires through wire tie C2 to control wire terminal block A.
	1	Connect a 2008 and later load center switch to a pre-2008 air-cooled generator: Wire 0 will not be utilized. Remove battery charger from the transfer switch. Connect N1 (BLU) to N1 (YEL), N2 (YEL) to N2 (YEL), 23 (BRN) to 23 (WHT), 194 (ORG) to 15B (RED) using UL approved wire nuts.	N1, N2, 23, 194, 15B, 0	Battery charger in transfer switch will not be utilized in operation of the generator.
	1	Connect a pre-2008 load center switch to a current or future air-cooled generator: Wire 0 will not be utilized. Connect N1 (BLU) to N1 (YEL), N2 (YEL) to N2 (YEL), 23 (BRN) to 23 (WHT), 194 (ORG) to 15B (RED) using UL approved wire nuts.	N1, N2, 23, 194, 15B, 0	Wire 194 changed to 15B on current model air-cooled generators.
0 VCC		0	NEGRO Núm. 3	CC (-) Cable común de conexión a tierra. Requerido si el generador está apareado con un interruptor de transferencia de gestión de alimentación inteligente Generac.
12 V c.c.		194 – c.c. (+)	ROUGE no 4	Pour les commandes de transfert.
12 VCC		194	ROJO núm. 4	CC (+) para los controles de transferencia
12 VDC		194 (Red #4)	D	DC (+) 12 VDC for Transfer Controls
120	1	Battery charger AC input to generator backed-up 120VAC circuit	120VAC hot, neutral	Connect via wire nuts
120 V c.a.		T1	BLEU no 3	Avec fusible 120 V c.a. pour le chargeur de la batterie; doit être branché pour que la batterie demeure chargée.
120 VAC		T1 (White #3)	B	Fused 120VAC for Battery Charger
120 VCA		T1	AZUL Núm. 3	Con fusible para el cargador de baterías (debe estar conectado para mantener la batería cargada, esté o no funcionando la unidad)
120/240	1	GENERATOR (STANDBY) source power cables to ATS GENERATOR supply terminals	E1, E2	200A models
120/240	1	Non-essential customer LOAD leads to LSS switch terminals	E1, E2	Load shed switch
120/240	1	UTILITY (NORMAL) power source cables to top of UTILITY SERVICE DISCONNECT circuit breaker	N1, N2	200A models
240	1	Transfer switch terminal lugs: connect utility source hot lines to N1 and N2; connect standby source hot lines (E1, E2) to E1 and E2; connect load lines from T1 and T2 to electrical load circuit; connect UTILITY, STANDBY and LOAD neutral lines to neutral block.	N1, N2, E1, E2, T1, T2	In 1-phase systems with a 2-pole transfer switch.
240 V c.a.		N1 et N2	JAUNE no 1 et no 2	Détectent les chutes et les hausses du réseau public.
240 VAC		N1 & N2 (Yellow #1 & #2)	A	Sensing for Utility Dropout and Pickup
240 VCA		N1 y N2	AMARILLO Núm. 1 y Núm. 2	Detección de desenganche y activación del servicio público
DC		0 (Black #3)	C	DC (-) Common Ground Wire

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Aftermarket parts that fit this engine

A0000501971 FridayParts $109.99 0G3224TA FridayParts $29.99 0G3224TB FridayParts $29.99 FP-XP-0033262

Parts listed by aftermarket suppliers as fitting this engine — leads compiled from supplier catalogs; verify the exact part for your serial number.

Common questions

What is the oil capacity of the Generac GT-990?

The Generac GT-990 engine has an oil capacity of 1.5 liters.

What is the displacement of the Generac GT-990?

The Generac GT-990 has a displacement of 992.0 liters with 2 cylinders.

Which generators use the Generac GT-990 engine?

The Generac GT-990 powers 4 generator set(s), including Generac 8.1 GN, Generac Model 004666, Generac Model 005011, Power Systems GT-990.

How often should you change the oil in the Generac GT-990?

The Generac GT-990 oil change interval is every 150 hours.

What is a common problem with the Generac GT-990 engine?

A commonly reported issue on generators using the Generac GT-990 is: Wiring Error ALARM.