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Generac GN-220 Engine

The Generac GN-220 is a 0.22 L 1-cylinder air-cooled engine rated at 4200 rpm. It powers generator sets from Generac and Magnum, including the Centurion 3500, IMPACT-34 plus, Impact-36 plus and Impact-36G. It holds 0.8 L (0.2 gal) of oil.

Also known as: Generac GN-220, GN-220

0.22 L

Displacement

Cylinders

4200 rpm

Rated speed

0.8 L

Oil capacity

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

Engine specifications

Oil capacity	0.8 L
Displacement	0.22 L
Cylinders	1
Aspiration	air-cooled
Rated speed	4200 rpm

Generator sets powered by this engine

Shared across brands: Generac, Magnum

Generac Centurion 3500Generac IMPACT-34 plusGenerac Impact-36 plusGenerac Impact-36GGenerac NP-30GGenerac NP-40GMagnum MLT4000S

How to read your Generac engine serial & model number →

Common problems

Engine cranks but won't start
Cause: Out of fuel
Fix: Replenish fuel
Engine will not start or starts hard and runs rough (poor compression)
Cause: Loose cylinder head bolts
Engine won't crank
Cause: 15 amp fuse is blown
Fix: Replace 15 amp fuse
Engine starts, shuts down when Start/Stop switch is released
Cause: Engine oil is low
Fix: Check oil; add as needed
Engine will not start, spark plug is DRY
Cause: Carburetor gasket(s) leaking; Fuel line plugged or shutoff valve not opening; Intake valve stuck closed; Inoperative fuel pump; Clogged fuel filter
Fix: Adjust or repair carburetor or fuel system as necessary
Engine will not crank
Cause: 15 amp fuse bad
Fix: Replace bad fuse
Engine starts, but then shuts down after startup
Cause: A problem could exist in either the generator computer system or in the engine DC control system
Fix: Isolate the CCG system using the test fixture; if the engine starts and shuts down, check engine oil level (if oil level is low, replenish as necessary; if oil level is NOT low, go to Test 26); if engine was shutting down after startup, but does not shut down during this test, the problem is in the CCG system, go to Test 27
Engine starts but Stepper Motor does not move. Shut down occurs after several seconds
Cause: Power Supply winding (PS1, PS2) is open
Fix: Repair or replace bad wire(s) PS1/PS2 or replace Stator
Engine shuts down but overspeed above 4500 rpm did not occur
Cause: One of four power windings in Stator is open
Fix: Repair/replace bad wire(s) AC1/AC2 or SL1/SL2 or replace Stator
Engine shutdown initiated by CCG board
Cause: Over-voltage
Priming function does not work
Cause: 15 amp fuse is bad
Fix: Replace bad fuse
Engine will not start, spark plug is WET
Cause: Overchoking; Water in fuel; Excessively rich fuel mixture; Intake valve stuck open
Fix: Adjust or repair carburetor or fuel system as necessary
Engine will not start (spark plug DRY)
Cause: Carburetor gasket(s) leaking
Fix: Adjust or repair carburetor or fuel system as necessary
Engine speed is maintained and no-load voltage is good. However, when load is applied output voltage drops and engine shuts down
Cause: Carburetor linkage sticking with throttle partly open
Fix: Repair sticking throttle
Start/Stop switch at Stop, engine continues to run
Cause: Defective Start/Stop switch
Fix: Replace switch

Compiled from service & troubleshooting documentation across every generator set that uses the Generac GN-220.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter	Paper element		078601	25 hr	Amazon eBay $10.67
Fuel filter			086311	100 hr	eBay
Oil filter			070185	100 hr	Amazon eBay $30.00 NAPA $3.59 FridayParts $45.99
Battery	Inspect battery posts and cables for tightness, corrosion; check battery fluid level, fill with distilled water only		—
Belt			—
Oil	Recommended oil: API SF, SG or SH	950.0 L	—	100 hr
Spark plug			072347	500 hr	eBay $1.99

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 crankcase oil level	Check	8 hr		or before each use
Engine oil level	Check	8 hr		or before each use
Oil filter	Change	50 hr		First service — first filter change
Air cleaner paper filter	Clean	25 hr	12 mo	whichever comes first
Air cleaner paper filter	Replace	25 hr	12 mo	Replace if too dirty
Foam Precleaner	Clean	25 hr	3 mo	Whichever occurs first; clean/re-oil
Paper air filter	Clean	100 hr	12 mo	whichever comes first
Engine oil	Change	100 hr		First service — thereafter; more frequently under heavy load or high ambient temperatures
Engine oil filter	Replace	50 hr		First service — thereafter
Engine valve clearance	Adjust	50 hr		First service — After the first 50 hours of operation; break-in period one time.
Oil filter	Replace	100 hr		First service — thereafter
Spark Arrestor Screen	Inspect	50 hr	12 mo	Inspect and clean every 50 hours or once each year
Valve clearance	Adjust	50 hr		First service — after first 50 hours of operation
Air Pre-filter	Clean	100 hr		100 Hours
Air intake	Clean	100 hr		Clean all foreign material from the air intake at least once every 100 hours.
Air intake screen	Clean	100 hr		clean more often if necessary
Engine Oil/Filter	Change	100 hr		100 Hours
Engine oil and oil filter	Change	100 hr		First service — Change more frequently under heavy load or high ambient temperature
Engine spark plug	Clean	100 hr		Clean or replace and set gap to 0.030 inch (0.76mm) every 100 hours
Fuel filter	Replace	400 hr	12 mo	whichever occurs first
Paper filter	Clean	100 hr	12 mo	Once each year or every 100 hours; clean or replace
Spark Plug	Adjust	100 hr		Clean and reset gap every 100 hours
Spark arrestor	Clean	100 hr		Inspect and clean spark arrestor
Spark arrestor muffler	Inspect	100 hr
Spark plug	Clean	100 hr		clean and set gap to 0.030 inch
Spark plug gap	Adjust	100 hr		Reset to 0.030 inch (0.76mm)
Spark plugs	Inspect	100 hr		Inspect and clean
Paper Air Filter Element	Replace	250 hr		250 Hours
Spark Plugs	Replace	500 hr		500 Hours
Spark plug	Replace	500 hr		Replace the spark plug every 500 hours, or if reuse is questionable.
Valve lash	Adjust	500 hr		First service — First at 50 hours, then every 500 hours
Battery	Test		6 mo	Every six months: check state of charge and condition
Battery state of charge	Test		6 mo	every six months, by automotive service facility
Battery state of charge and condition	Test		6 mo	Have checked with an automotive type battery hydrometer
Leveling jacks	Lubricate		12 mo	Jack maintenance performed at least annually.
Trailer wheel bearings	Lubricate		12 mo	Minimum every 12 months or 12,000 miles (19,312 km); more frequent in dusty or damp conditions.

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	Carburetor throttle lever stop tab to stop block gap	0.003	inch
Clearance	Clearance between exhaust system parts and combustible material	3 (76mm)	inch
Clearance	Clearance between fuel line and exhaust system parts	2	inch
Clearance	Clearance between generator and compartment walls/ceiling	1 (2 recommended)	inch	after metal lining and sound insulation installed
Clearance	Crankshaft end play (allowable)	0.006-0.023	inch (0.14-0.60mm)
Clearance	Engine valve clearance	0.001-0.003	inch (0.03-0.07 mm)	engine at room temperature and piston at Top Dead Center of compression stroke
Clearance	Exhaust system clearance to combustible material	3	inches (76mm)	minimum
Clearance	Exhaust system extension past outer edge of vehicle	1	inch (25mm)	minimum
Clearance	Exhaust system to combustible material	3	inches (76 mm)	minimum
Clearance	Exhaust system to combustible material clearance	3	inches	(76mm) minimum
Clearance	Fuel line clearance to exhaust system parts	2	inches	minimum
Clearance	Oil pump tip clearance	0.0000-0.0010 design / 0.004 wear limit	inch (0.000-0.025mm)	measured on shaft in oil sump
Clearance	Oil ring end gap	0.015-0.055 design / 0.062 wear limit	inch	ring pushed down 2.75 inch
Clearance	Piston ring-to-groove side clearance	0.0004-0.0014	inch (0.012-0.034mm)
Clearance	Second ring end gap	0.006-0.016 design / 0.024 wear limit	inch	ring pushed down 2.75 inch
Clearance	Throttle lever stop tab to stop block gap	0.003	inch (0.08-0.5mm)	engine coasting to a stop
Clearance	Throttle linkage gap between stop tab and stop block	0.003	inch (0.08-0.5mm)	minimum gap for throttle linkage adjustment
Clearance	Top ring end gap	0.005-0.016 design / 0.024 wear limit	inch (0.15-0.40mm)	ring pushed down 2.75 inch (70mm)
Gap	Gap between throttle lever stop tab and carburetor stop block	0.003	inch (0.08-0.5mm)
Gap	Spark plug gap	0.030	inch
Gap	Spark plug gap	0.76	mm
Gap	Spark plug gap (metric)	0.76	mm
Gap	Throttle lever stop tab to carburetor stop block gap	0.003	inch (0.08-0.5mm)
Gap	Throttle linkage stop tab to stop block gap	0.003	inch
Other	Battery cable voltage drop	0.12	volts per 100 amperes of cranking current	maximum
Other	Battery charge current	2	amperes (max)
Other	Battery compartment ventilation opening	2	square inches at top
Other	Carburetor high altitude jetting	5000	feet	altitudes in excess of 5000 feet; consult Authorized Service Facility
Other	Cranking current rating	100	DC amperes	approximately
Other	Engine crankcase and oil filter oil capacity	950 (1 quart)	ml
Other	Engine oil capacity	950	mL (1 quart)
Other	Exhaust system extension past outer edge of vehicle	1 (25mm)	inch
Other	Flexible fuel hose length	6	inches	at least 6 inches longer than needed
Other	Flexible fuel hose length	at least 6 inches longer than needed	inch
Other	Fuel pickup tube length (shared tank)	2 to 3 inches shorter than vehicle engine pickup tube	inch
Other	Generator compartment clearance around generator	1	inch (2 inches recommended)	all sides and ceiling
Other	Generator fuel pickup tube shorter than vehicle engine pickup tube	2 to 3	inches	recommended
Other	Generator mounting bolts	3/8"-16		four hardened steel bolts Grade 5; at least 3 threads visible past lock nuts when tight
Other	Generator restraint bolts	3/8"-16 hardened steel, Grade 5		at least 3 threads visible past retaining lock nuts
Other	Ignition timing	29 degrees BTDC (at higher speeds); 15-18 degrees BTDC at cranking speeds	degrees BTDC
Other	LED driver voltage	up to 250V	V
Other	Maximum continuous cranking time	15	seconds	release start/stop switch if engine does not start
Other	Maximum highway towing speed	45	mph (72 km/h)
Other	Maximum off-road towing speed	10	mph (16 km/h)
Other	Minimum acceptable Stator insulation resistance	rated volts/1000 + 1	megohm
Other	Minimum air inlet opening (unrestricted)	40	square inches	divide by free air inlet area percentage for restricted openings
Other	Minimum unrestricted cooling air inlet opening	40	square inches	divide by percentage free air inlet area to compensate for restrictions
Other	Oil filter tightening after gasket contacts adapter	3/4 to one	turn (by hand)
Other	Recommended minimum LP gas flow rate for air-cooled Impact-34 plus series generators	67	cubic feet per hour
Other	Standard cylinder bore diameter	2.7560-2.7570 (GN-190) / 2.953-2.954 (GN-220)	inches
Other	Valve seat width	0.034-0.044 design / 0.064 wear limit	inch (0.87-1.13mm)	grind seats to 45 deg, 0.040 inch width
Pressure	Engine compression pressure	60 nominal / 55 minimum	psi	cold engine while cranking
Pressure	Engine compression pressure (while cranking, cold engine)	55	psi	minimum allowable
Pressure	Engine compression pressure (while cranking, cold engine)	60	psi	nominal
Pressure	Engine compression pressure, minimum allowable	55	psi	while cranking, cold engine
Pressure	Engine compression pressure, nominal	60	psi	while cranking, cold engine
Pressure	Fuel pump outlet pressure	2.0 to 3.5	psi	at zero delivery
Pressure	Fuel pump pressure at zero delivery	2.0 to 3.5	psi
Pressure	Gas pressure at inlet to gaseous fuel solenoid valve and secondary regulator	11	inches water column	Do not exceed 14 inches water column
Pressure	LP fuel system leak test pressure	90	psi (620 kPa)	minimum; use soap and water or equivalent

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	10W-30	API Service Classification SF, SG or SH			10°F to 100°F
Engine oil	15W-40	API Service Classification SF, SG or SH			0°F to 80°F
Engine oil	5W-30	API Service Classification SF, SG or SH			-20°F to 50°F; recommended during winter months
Engine oil	SAE 10W-30	API 'For Service SF'			Used to refill crankcase when removing unit from service for storage
Engine oil	SAE 15W-40				Viscosity chart range 0F to 80F
Engine oil	SAE 30			950.0 ml	Summer months; acceptable substitute is SAE 10W-30.
Engine oil	SAE 30 (summer); SAE 5W-30 (winter); SAE 10W-30 acceptable substitute; DO NOT USE SAE 10W-40	API Service Classification SF, SG or SH		0.8 L	Crankcase and oil filter capacity approximately 800 mL or .84 U.S. quarts. Viscosity chart: 32 F and higher; 10 F to 100 F; 0 F to 80 F; -20 F to 50 F with grades 5W-30, 10W-30, 15W-40, 30. Do not use special additives.
Engine oil	SAE 30 (summer); SAE 5W-30 (winter); SAE 10W-30 acceptable summer substitute			950.0 mL (1 quart)	Do not use SAE 10W-40. Use no special additives.
Engine oil	SAE 30 (summer); SAE 5W30 (winter)	API service classification SF, SG or SH		950.0 ml	SAE 10W-30 acceptable summer substitute; DO NOT USE SAE 10W-40. Crankcase and oil filter capacity about 950ml or about 1 U.S. quart. Use no special additives.
Engine oil	SAE 30 (summer); acceptable substitute SAE 10W-30 (summer)			950.0 ml (about 1 quart)	DO NOT USE SAE 10W-40
Engine oil	SAE 30 (with filter change)			946.0 ml	Engine crankcase oil capacity with oil filter change is about 1 U.S. quart (946 ml)
Engine oil	SAE 30 summer (SAE 10W-30 acceptable substitute); SAE 5W30 winter	API service classification SF, SG or SH		950.0 ml	Crankcase and oil filter capacity about 950ml or about 1 U.S. quart; do not use SAE 10W-40; use no special additives
Engine oil	SAE 5W-20 or 5W-30	For Service SC, SD, SE, SF or SG	below 0°C		Winter months (below 32 F / 0 C); DO NOT USE SAE 10W-40
Engine oil	SAE 5W-20 or SAE 5W-30	For Service SC, SD, SE, SF or SG	below 0°C		Winter months (below 32 F / 0 C); do not use SAE 10W-40
Engine oil	SAE 5W-30	API Service Classification SF, SG or SH			Winter months; -20F to 50F
Engine oil	SAE 5W30			950.0 ml	Winter months; DO NOT USE SAE 10W-40.
Engine oil	SAE 5W30 (winter)			950.0 ml (about 1 quart)
Engine oil	SAE 30 (SAE 10W-30 acceptable substitute)	For Service SC, SD, SE, SF or SG	above 0°C	946.0 ml	Summer months (above 32 F / 0 C); DO NOT USE SAE 10W-40; capacity with oil filter change about 1 U.S. quart (946ml); without oil filter change about 29 fluid ounces (850ml)
Fuel	Clean, fresh, UNLEADED regular grade gasoline; leaded Regular acceptable substitute				Do not use gasohol; if gasoline containing alcohol is used it must not contain more than 10% ethanol. DO NOT USE GASOLINE CONTAINING METHANOL. DO NOT MIX OIL WITH THE GASOLINE.
Fuel	High quality UNLEADED gasoline	Leaded REGULAR grade acceptable substitute			If gasoline contains alcohol it must not contain more than 10 percent ethanol and must be removed during storage. Do NOT use gasoline containing methanol.
Fuel	High quality UNLEADED gasoline (leaded REGULAR grade acceptable substitute)				If gasoline contains alcohol it must not contain more than 10 percent ethanol; do NOT use gasoline containing methanol
Fuel	High quality unleaded gasoline; leaded regular grade acceptable substitute				If gasoline contains alcohol it must not contain more than 10 percent ethanol and must be removed from the tank during storage; do NOT use any gasoline containing methanol
Fuel	LP (liquid propane gas)			7.9 lbs	Use clean liquid propane gas only. Fuel tank capacity 7.9 lbs (29.9 kg). LP, 4-stroke engine.
Fuel	LP gas (propane, butane, or mixture)				Vapor withdrawal type fuel system required; propane vaporizes at temperatures as low as -20°F (-29°C)
Fuel	LP gas (propane/butane vapor withdrawal)				Impact-34 plus (LP unit); propane vaporizes to -20F(-29C), butane to 32F(0C)
Fuel	LP gas (propane/butane)	Vapor withdrawal type fuel system			LP units.
Fuel	LP gas (vapor withdrawal only)				Gaseous fuel systems; generator requires at least 67 cubic feet of gas per hour
Fuel	Unleaded gasoline	High quality unleaded; leaded REGULAR grade acceptable substitute; ethanol maximum 10 percent; no methanol			Gasoline units.
Fuel	Unleaded gasoline (Leaded REGULAR grade acceptable substitute)	Not more than 10 percent ethanol if alcohol-containing; no methanol			High quality unleaded reduces lead and carbon deposits
Fuel	Unleaded gasoline (leaded regular acceptable substitute); no more than 10% ethanol; no methanol				Impact-36 plus (gasoline unit)

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 Throttle Linkage adjustment

⚠ Do not overbend the spring clip or the clip will lose its clamping force

Tools: Pliers

Start generator, then shut it down right away.
Observe throttle lever rotating counterclockwise as engine coasts to stop.
Check gap of 0.003 inch (0.08-0.5mm) between stop tab and carburetor stop block.
With pliers, lightly compress the spring clip on the carburetor lever arm.
Slide linkage rod through clip and rotate throttle lever to set gap.
Release spring clip to secure adjustment.

Adjust Valve Clearance adjustment

Tools: Allen wrench, Feeler gauge, Crows foot

Engine at room temperature, piston at TDC of compression stroke.
Loosen the rocker arm jam nut.
Turn pivot ball stud with allen wrench while checking clearance with feeler gauge.
When clearance is correct, hold pivot ball stud and tighten jam nut with crows foot.
Tighten jam nut to 65-85 inch-pounds torque.
Recheck valve clearance to be sure it did not change.

Adjusting Throttle Linkage adjustment

⚠ Do not overbend the spring clip or the clip will lose its clamping force.

Tools: Pliers

Start generator, then shut down right away; observe throttle lever rotate counterclockwise.
Check for gap of 0.003 inch (0.08-0.5mm) between stop tab and stop block.
With pliers, lightly compress spring clip on carburetor lever arm to slide linkage rod freely.
Rotate throttle lever to set gap to 0.003 inch (0.08-0.5mm).
Release spring clip to secure adjustment.

Adjusting Valve Clearance adjustment

Tools: allen wrench, feeler gauge, crows foot

Engine must be at room temperature with piston at TDC of compression stroke.
Loosen the rocker arm jam nut.
Turn the pivot ball stud with an allen wrench while checking clearance with a feeler gauge.
Correct clearance is 0.001-0.003 inch (0.03-0.07 mm).
Hold the pivot ball stud and tighten the rocker arm jam nut to 65-85 inch-pounds.
After tightening the jam nut, recheck valve clearance.

Adjusting the Valve Clearance adjustment

Tools: Allen wrench, Feeler gauge, Crows foot

Ensure the engine is at room temperature and the piston is at Top Dead Center of its compression stroke with both valves closed.
Loosen the rocker arm jam nut.
Use an allen wrench to turn the pivot ball stub while checking clearance between the rocker arm and valve stem with a feeler gauge.
When clearance is correct, hold the pivot ball stud with the allen wrench and tighten the rocker arm jam nut with a crows foot to 65-85 in-lbs (7-10 Nm).
Recheck valve clearance after tightening the jam nut.

Carburetor Adjustment (Idle Jet) adjustment

⚠ Do NOT adjust the fuel-air mixture excessively lean; can result in engine damage.

Turn the idle jet inward (clockwise) until it just contacts its seat; do not force.
Turn the idle jet outward (counterclockwise) 1-1/8 turns.
Start engine and let it warm up about five minutes.
With engine at no-load, turn idle jet clockwise (leaner) until speed decreases or fluctuates.
Turn idle jet counterclockwise (richer) until speed decreases/fluctuates or black smoke appears.
Very slowly turn idle jet clockwise until speed just stabilizes or black smoke just stops.

Carburetor Idle Jet Adjustment adjustment

⚠ Do NOT adjust the fuel-air mixture excessively lean. An excessively lean mixture can result in engine damage.

Turn the idle jet inward (clockwise) until it just contacts its seat; DO NOT FORCE.
Turn the idle jet outward (counterclockwise) 1-1/8 turns to allow the engine to start and warm up.
Run the engine at no-load and turn the idle jet clockwise (leaner) until engine speed starts to decrease or fluctuate.
Turn the idle jet counterclockwise (richer) until speed decreases/fluctuates or black exhaust smoke appears.
Very slowly turn the idle jet clockwise (leaner) until engine speed just stabilizes or black smoke just stops.

Throttle Linkage Adjustment adjustment

⚠ Do not overbend the spring clip or it will lose its clamping force

Tools: pliers

Start generator, then shut it down right away and observe throttle lever rotate counterclockwise as engine coasts to stop
Verify gap of 0.003 inch (0.08-0.5mm) between stop tab on throttle lever arm and stop block on carburetor die casting
With pliers, lightly compress spring clip on carburetor lever arm to allow linkage rod to slide freely
Rotate throttle lever to adjust gap to 0.003 inch clearance
Release spring clip to secure adjustment

Valve Clearance Adjustment adjustment

Tools: Allen wrench, feeler gauge, torque wrench, crow's foot

Rotate the crankshaft until the piston is at top dead center (TDC) of its compression stroke; both valves should be closed.
Loosen the rocker arm jam nut.
Use an Allen wrench to turn the pivot ball stud while checking clearance between rocker arm and valve stem with a feeler gauge.
When clearance is correct, hold the pivot ball stud with the Allen wrench while tightening the jam nut with a crow's foot.
Recheck the valve clearance after tightening the jam nut.

Spark Test (Ignition System) diagnostic

Tools: spark tester

Disconnect the high tension lead from the spark plug.
Attach the spark plug high tension lead to the spark tester terminal.
Connect the spark tester clamp to the engine cylinder head.
Crank the engine rapidly; the engine must be turning at 350 rpm or more.
If spark jumps the tester gap, the ignition system is operating satisfactorily.

Test All Stator Windings to Ground (Insulation Resistance) diagnostic

⚠ All Stator leads must be isolated from other components, especially circuit boards, before performing tests. The high voltages used in testing insulation resistance will damage electronic components.

Tools: Hi-Pot tester or Megohmmeter

Disconnect and isolate all Stator leads before starting tests.
Connect the ends of all Stator leads together; make sure none touch any terminal or part of the generator.
Connect one tester probe to the junction of all Stator leads and the other to a clean frame ground on the Stator.
Apply a voltage of 1000 volts for about 1 second.
If insulation resistance is low, clean and dry the Stator and repeat the test; if it fails again replace the Stator assembly.

Testing the Battery Charge Circuit diagnostic

Tools: VOM (volt-ohm-milliammeter)

Disconnect Wire 77 at the Battery Charge Rectifier (BCR).
Disconnect Stator output Wire 66 at the BCR.
Disconnect Wire 55.
Set a VOM to Rx1 and zero the meter.
Connect the VOM test leads across Wires 77 and 55, then across Wires 66 and 55; note both resistance readings.
With the unit running, measure AC voltage at the Wires 66 and 77 terminals; if no AC voltage, an open circuit exists in Wire 66 or 77.
With engine running, check for DC voltage between the BCR Wire 55 and frame ground; if AC was present but DC is not, the BCR is defective.

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
		Battery Charge Rectifier (BCR)	66 (Brown)
		Battery Charge Rectifier BCR	77 (Brown)	Stator lead
		CCG Circuit Board (CCB)	PS1 (Brown)	Stator lead
		CCG Circuit Board (CONN4)	PS1 (Brown)	Pin 1 of CONN4 connector
		DC output leads	+DC (Red), -DC (Blue), Return (Black), Ground (Green)	Route from generator DC output leads through approved flexible conduit to terminal block in DC junction box on inverter
		Engine Controller Board (J1 pin 1)	56	Delivers 12 VDC to Starter Contactor while cranking only
		Genistor (G)	SL2 (Brown)	Stator lead
		Grounding Terminal	55 (Black)	Stator lead
		Ignition Sensor	RED (+)	Battery voltage from Ignition Module to Ignition Sensor
		Lead 11 (Blue) connects to Main Circuit Breaker CB1	11 / Blue
		Lead 55 (Black) connects to Grounding Terminal	55 / Black
		Lead 66 (Brown) connects to Battery Charge Rectifier BCR	66 / Brown
		Lead 77 (Brown) connects to Battery Charge Rectifier BCR	77 / Brown
		Lead AC1 (Gray) connects to Genistor	AC1 / Gray
		Lead AC2 (Yellow) connects to Genistor	AC2 / Yellow
		Lead PS1 (Brown) connects to CCG Circuit Board (CCB)	PS1 / Brown
		Lead PS2 (Yellow) connects to CCG Circuit Board (CCB)	PS2 / Yellow
		Lead SL1 (Orange) connects to Genistor	SL1 / Orange
		Lead SL2 (Brown) connects to Genistor	SL2 / Brown
		Lead TIM1 (Orange) connects to CCG Circuit Board (CCB)	TIM1 / Orange
		Lead TIM2 (Gray) connects to CCG Circuit Board (CCB)	TIM2 / Gray
		Main Circuit Breaker (CB1)	11 (Blue)
		Main Circuit Breaker CB1	11 (Blue)	Stator lead
		Remote panel receptacle	Wire #0 (Ground), Wire #14 (Engine run signal), Wire #17 (Crank), Wire #18 (Stop)	Optional remote-mounted start/stop panel
12		Battery cables	Positive to large lug on starter contactor; Negative to frame ground	Cable size by length: 0-10 ft (0-3m): No.2; 11-15 ft (3.4-4.5m): 0; 16-20 ft (4.5-6m): 000. For warm weather use No.2 cable up to 20 feet.
120	Single	120 Volts only (line-to-neutral)	BLACK (hot), WHITE (grounded neutral), GREEN (ground)	Dual stator AC power windings; neutral bonded to frame of engine-generator; protected by 30-amp circuit breaker (CB1); rated 3,400 watts (3.4 kW) at 28.3 amperes
120	Single	Leads BLACK to WHITE (line-to-neutral)	BLACK (hot), WHITE (grounded neutral), GREEN (ground)	Grounded neutral bonded to frame of engine-generator; protected by 30-amp circuit breaker (CB1); dual stator windings
120	Single	Line-to-neutral; BLACK (hot), WHITE (grounded neutral), GREEN ground	BLACK, WHITE, GREEN	Neutral bonded to frame of engine-generator; protected by 30-amp circuit breaker CB1; drawing 0D8063-D
120	Single Phase	AC output	T1 (Black), T2 (White), Green ground	From AC output junction box on inverter to double-pole double-throw transfer switch or approved isolation receptacle.
120	Single Phase	T1 (black) is hot; T2 (white) is neutral	T1 (black), T2 (white), green ground wire	Grounded neutral; lead T2 internally connected to ground. Line T1 protected against overload by the circuit breaker (CB1). Use T1-T2 for 120 volts, 1-phase, 60 Hz AC loads. Single voltage AC connection system.

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

Common questions

What is the oil capacity of the Generac GN-220?

The Generac GN-220 engine has an oil capacity of 0.8 liters.

What is the displacement of the Generac GN-220?

The Generac GN-220 has a displacement of 0.22 liters with 1 cylinders.

Which generators use the Generac GN-220 engine?

The Generac GN-220 powers 7 generator set(s), including Generac Centurion 3500, Generac IMPACT-34 plus, Generac Impact-36 plus, Generac Impact-36G, Generac NP-30G.

How often should you change the oil in the Generac GN-220?

The Generac GN-220 oil change interval is every 100 hours.

What is a common problem with the Generac GN-220 engine?

A commonly reported issue on generators using the Generac GN-220 is: Engine cranks but won't start. Cause: Out of fuel. Fix: Replenish fuel.