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Generac GP8000E Engine

Name: Generac GP8000E Engine
Brand: Generac

The Generac GP8000E is an engine rated at 3600 rpm. It powers generator sets from Generac, including the GP8000. It holds 1 L (0.3 gal) of oil.

Also known as: Generac GP8000E

3600 rpm

Rated speed

1.0 L

Oil capacity

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

Engine specifications

Oil capacity	1.0 L
Rated speed	3600 rpm

Generator sets powered by this engine

Generac GP8000

How to read your Generac engine serial & model number →

Common problems

Recoil Cord Will Not Pull
Cause: BAD
Fix: TEST 49 – TEST RECOIL FUNCTION TEST 50 – TEST ENGINE FUNCTION REPAIR OR REPLACE
Engine ‘Hunts’ / Erratic Idle
Cause: NO SURGING STILL SURGING
Fix: TEST 29 – CHECK CARBURETION GOOD TEST 40 – CHECK AND ADJUST GOVERNOR
Engine Will Not Crank
Cause: NO VOLTAGE MEASURED 12 VDC MEASURED
Fix: RECHARGE OR REPLACE BATTERY – CLEAN, REPAIR OR REPLACE BAD CABLE(S) BAD REPLACE BAD GOOD NO VOLTAGE MEASURED BAD 12 VDC MEASURED REPLACE STARTER MOTOR IF DEFECTIVE GOOD CHECK FOR MECHANICAL BINDING OF THE ENGINE OR ROTOR
Engine Turns Over But Will Not Start
Cause: NO SPARK
Fix: TEST 39 – REMOVE WIRE 18 / SHUTDOWN LEAD NO SPARK GOOD BAD REPLACE SWITCH BAD CHECK ENGINE OIL LEVEL TEST 45 – CHECK OIL LEVEL SWITCH TEST 24 – TEST OFF-ON SWITCH REPLACE SWITCH REPLENISH OIL REPLACE LOW OIL ALARM GOOD OIL LEVEL O.K. OIL LEVEL LOW BAD
Engine Starts Hard and Runs Rough
Cause: ADJUST VALVES AND RETEST
Fix: BAD TEST 40 – CHECK AND ADJUST GOVERNOR TEST 38 – CHECK FLYWHEEL

Compiled from service & troubleshooting documentation across every generator set that uses the Generac GP8000E.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter	N/A		—	200 hr
Oil filter	Service Air Filter		—	200 hr
Oil	Oil Change Interval	1.0 L	0J00620106	100 hr	Amazon $8.99 eBay $35.00 FridayParts $32.07
Spark plug	N/A		0J00620106		Amazon $8.99 eBay $35.00 FridayParts $32.07

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

Service intervals

Item	Action	Hours	Months	Notes
Engine oil level	Check	8 hr		Prior to each use, or every 8 hours of operation
Engine oil	Change	100 hr	12 mo	Every 100 hours or every year; change after first 30 hours of operation, then every season
Spark arrestor	Inspect	100 hr	12 mo	Every 100 hours or every year
Air cleaner filter	Clean	200 hr	12 mo	Every 200 hours or every year; replace if cannot be adequately cleaned
Valve clearance	Check	300 hr	12 mo	First service — Check/adjust after first 50 hours, then every 300 hours thereafter or every year
Spark plug	Replace		12 mo	Every year

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	Flywheel magnet attraction distance (screwdriver test)	3/4 (19mm)	inch
Gap	Spark plug gap	0.028-0.031	inch (0.70-0.80 mm)
Gap	Spark plug gap (GP1800/GP3250/GP5000/GP5500/GP6500)	0.028"-0.031" (0.7-0.8mm)	inch
Gap	Spark plug gap (GP7000/GP8000)	0.030" (0.76mm)	inch
Other	1.5 Amp fuse rating	1.5	Amp
Other	AC output load test - frequency should not drop below	59	Hertz	load applied
Other	Capacitor rating - Alternator Configuration A	47	µf (440 VAC)
Other	Capacitor rating - Alternator Configuration B	28	µf
Other	Capacitor test tolerance	± 5	µf
Other	Cylinder leak down - normally acceptable leakage	20	percent
Other	Nominal amp draw of starter in generator	60	amps
Other	Starter motor maximum amps	50	Amps	performance test
Pressure	Cylinder leak down - minimum air source	90	psi
Pressure	Cylinder leak down - regulated test pressure	80	psi
Pressure	Engine oil pressure - shut down threshold	below about 10	psi	engine running
Pressure	Minimum allowable compression pressure	60	psi	cold engine
Pressure	Normal engine oil pressure	35-40	psi	engine running
Pressure	Oil pressure switch rating	10	psi	single cylinder engines
Resistance	Brushless DPE winding resistance (Wire 2 to Wire 6)	0.97 and 1.13	Ohms
Resistance	Brushless stator winding resistance (11-22, 33-44)	0.12-0.14	Ohms
Resistance	Exciter Windings - GP1800 (alt 0H8255/0J0819)	2.53	Ohms
Resistance	Exciter Windings - GP3250 (alt 0H2626/0H3578)	1.72	Ohms
Resistance	Exciter Windings - GP5500/GP/LP5500 (alt 0G9769/0J8363)	2.81	Ohms
Resistance	Exciter Windings - GP6500E (alt 0H9920/0K1291)	2.9 ± 10%	Ohms
Resistance	Exciter Windings - GP7500E DF-CO (alt A0001920613/A0000121536)	1.928	Ohms
Resistance	Exciter Windings - GP8000E COSTCO (alt 0J8438/0K9791)	1.626	Ohms
Resistance	Exciter Windings - LP3250 (alt 0J2561/0J6032)	2	Ohms
Resistance	Power Windings - GP1800 (alt 0H8255/0J0819)	0.798	Ohms
Resistance	Power Windings - GP3250 (alt 0H2626/0H3578)	0.62	Ohms
Resistance	Power Windings - GP5500/GP/LP5500 (alt 0G9769/0J8363)	0.681	Ohms
Resistance	Power Windings - GP6500E (alt 0H9920/0K1291)	0.6 ± 10%	Ohms
Resistance	Power Windings - GP7500E (alt 0J1927/0K8981)	1.62	Ohms
Resistance	Power Windings - GP7500E DF-CO (alt A0001920613/A0000121536)	0.491	Ohms
Resistance	Power Windings - GP8000E COSTCO (alt 0J8438/0K9791)	0.471	Ohms
Resistance	Power Windings - LP3250 (alt 0J2561/0J6032)	0.63	Ohms
Resistance	Receptacle panel / stator winding continuity	0.01 and 0.02	Ohms
Resistance	Rotor Windings - GP1800 (alt 0H8255/0J0819)	29.4	Ohms
Resistance	Rotor Windings - GP3250 (alt 0H2626/0H3578)	31	Ohms
Resistance	Rotor Windings - GP5500/GP/LP5500 (alt 0G9769/0J8363)	61.48	Ohms
Resistance	Rotor Windings - GP6500E (alt 0H9920/0K1291)	69 ± 10%	Ohms
Resistance	Rotor Windings - GP7500E (alt 0J1927/0K8981)	58.8	Ohms
Resistance	Rotor Windings - GP7500E DF-CO (alt A0001920613/A0000121536)	52.42	Ohms
Resistance	Rotor Windings - GP8000E COSTCO (alt 0J8438/0K9791)	52.17	Ohms
Resistance	Rotor Windings - LP3250 (alt 0J2561/0J6032)	58	Ohms
Speed	Acceptable running limits (389/206/163cc)	59-61	Hertz	running
Speed	Acceptable running limits (410cc)	59-62	Hertz	running
Speed	Load frequency limit (minimum)	59	Hertz	rated load applied
Speed	Minimum engine cranking speed for spark test	350	rpm	cranking
Speed	No-load AC frequency	62.0-62.5	hertz	running adjustment, no-load
Speed	No-load AC frequency	62.5 – 62.0	HZ	no-load
Speed	No-load frequency (389/206/163cc governor adjust)	62.0 - 62.5	hertz	no-load
Speed	No-load frequency (410cc governor adjust)	62.5	Hz	no-load
Speed	Starter motor minimum rpm	4500	rpm	performance test
Torque	Governor Lever Clamp Bolt	110	in-lbs (12.4 Nm)
Torque	Governor Lever Clamp Bolt	70	in-lbs (8 Nm)
Torque	Governor lever clamp bolt (389/206/163cc)	110	inch-pounds
Torque	Governor lever clamp bolt (410cc)	70 inch-pounds (8 Nm)	inch-pounds
Torque	Rocker Arm Jam Nut	14	ft-lbs (19 Nm)
Torque	Rocker Arm Jam Nut	6-9	ft-lbs (8-12 Nm)
Torque	Rocker Arm Jam Nut	7	ft-lbs (9.4 Nm)

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	Capacity	Notes
Engine oil	10W-30			Oil will need to be purchased separately based upon the recommendations listed.
Engine oil	5W30		0.6 liter	GP1800/GP3250 oil capacity 0.634 quart (0.6 liter)
Engine oil	SAE 30			Oil will need to be purchased separately based upon the recommendations listed.
Engine oil	SAE 30 / 10W-30 / Synthetic 5W-30		1.0 L	See chart in Add Engine Oil; use petroleum-based oil for break-in before synthetic
Engine oil	Synthetic 5W-30			Oil will need to be purchased separately based upon the recommendations listed.
Fuel	Clean, fresh, unleaded gasoline, minimum 87 octane/87 AKI (91 RON), up to 10% ethanol		29.9 L (7.9 gal)	DO NOT use E85 or gas/oil mix
Fuel	gasoline	fresh, clean gasoline		Shelf life on gasoline is 30 days; a fuel stabilizer must be used at all times

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
Red Short Flash	CO Module - Red Short Flash	Elevated level of CO in the area; module is functioning properly and protecting operators	Shutdown	Generator shuts down; module is functioning as intended

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

Procedures

Test 12 – Adjust Voltage Regulator adjustment

⚠ Ensure all material is clear of the alternator before proceeding.

Tools: VOM

Remove cover from end of alternator assembly.
Remove two screws holding down the voltage regulator (AVR).
Leave AVR connected to stator and brushes.
Set VOM to measure AC voltage.
Connect VOM across a 240VAC socket.
Set START-STOP-RUN switch to START.
Turn adjustment screw clockwise to increase voltage, counterclockwise to lower.

Test 20 - Check Spark Plugs / Test 23 - Check Valve Adjustment adjustment

Tools: feeler gauge, crow foot wrench

Adjust valve clearance with engine at room temperature
Position piston at TDC of compression stroke (both valves closed), or set intake/exhaust valve fully open method
Loosen rocker arm jam nut; turn pivot ball stud while checking clearance with a feeler gauge
When clearance is correct, hold pivot ball stud and tighten rocker arm jam nut to specified torque with a crow foot wrench
Recheck valve clearance to make sure it did not change
Install rocker arm cover with a new gasket

Test 27 - Check / Adjust Governor adjustment

Tools: AC frequency meter

Loosen governor clamp bolt
Hold governor lever at wide open throttle position
Rotate governor shaft counterclockwise (389/208/196cc) or clockwise (410cc) as far as it will go
Tighten governor lever clamp bolt to 110 in-lbs (389/208/196cc) or 70 in-lbs (410cc)
Turn speed adjustment screw counterclockwise three full turns to avoid overspeed
Start engine and let warm up under no-load
Connect AC frequency meter; no-load frequency should be 62.0-62.5 hertz
Turn speed adjust screw until frequency/RPM is within limits
Apply removable Loctite (Loctite 241) to speed adjust screw threads

Test 33 – Check Valve Adjustment adjustment

⚠ Use a new rocker arm cover gasket.

Tools: feeler gauge, allen wrench, crow's foot

Adjust valve clearance with engine at room temperature.
Position piston at TDC of compression stroke (both valves closed).
Loosen the rocker arm jam nut.
Turn pivot ball stud while checking clearance with a feeler gauge.
Hold stud with allen wrench and tighten jam nut to specified torque with a crow's foot.
Recheck valve clearance after tightening.

Test 40 – Check / Adjust Governor (389/206/163cc Engines) adjustment

⚠ Do not apply excessive torque to the governor shaft.

Tools: frequency meter

Loosen the governor lever clamp bolt.
Hold governor lever at full INC RPM; rotate governor shaft counterclockwise fully.
Tighten governor lever clamp bolt to 110 inch-pounds.
Turn speed adjustment screw counterclockwise three full turns.
Start engine and let it warm up and stabilize at no-load.
Connect frequency meter; set no-load frequency 62.0-62.5 hertz.
Add a drop of Loctite 241 to the speed adjust screw threads.

Test 41 – Check / Adjust Governor (410cc Engine) adjustment

Tools: frequency meter

Loosen the governor clamp bolt.
Hold governor lever at wide open throttle; rotate governor shaft clockwise fully.
Tighten governor lever clamp bolt to 70 inch-pounds (8 Nm).
Start generator; let it stabilize and warm up at no-load.
Connect frequency meter across generator AC output leads.
Turn the primary adjust screw to obtain a frequency of 62.5 Hz.

Test 1 – Check No-Load Voltage and Frequency diagnostic

Tools: VOM, AC frequency meter

Disconnect or turn OFF all electrical loads connected to the generator.
Set a VOM to measure AC voltage.
Reset all circuit breakers to the ON position.
Start engine and let it stabilize and warm up.
Place meter test leads into an outlet.
Read AC voltage; connect frequency meter and read frequency.

Test 23 – Check Start-Run-Stop Switch diagnostic

Tools: voltmeter (resistance)

Set a voltmeter to measure resistance.
Remove all wires from the START-RUN-STOP Switch.
Check terminal 2 to 1: CONTINUITY in START, INFINITY in STOP.
Check terminal 2 to 3: CONTINUITY in STOP, INFINITY in START.
Reconnect all wires to the switch.

Test 25 – Testing Starter Motor Performance diagnostic

⚠ DO NOT rotate engine with electric starter with spark plugs removed.

Tools: clamp-on ammeter, tachometer P/N 042223, 12 volt battery, starter test bracket

Remove starter motor and assemble to test bracket; clamp in vise.
Connect a fully charged 12 volt battery and clamp-on ammeter.
Activate the starter (jump terminal on Starter Contactor).
Note reading on clamp-on ammeter and tachometer.
Take readings after ammeter and tachometer stabilize (2-4 seconds).

Test 36 – Cylinder Leak Down / Compression Test diagnostic

Tools: cylinder leak down tester, compression gauge

Remove the spark plug.
Gain access to the flywheel and remove the valve cover.
Rotate crankshaft until piston reaches TDC (both valves closed).
Lock the flywheel at top dead center.
Attach leak down tester adapter to spark plug hole.
Connect an air source of at least 90 psi.
Adjust regulated pressure to 80 psi.
Read right hand gauge; 20 percent leakage is normally acceptable.

Test 41 - CO Module Verification Test diagnostic

⚠ Do NOT insert the drill bit into the LED holes; damage to the LEDs will occur

Tools: 3/64 inch drill bit

Do not install CO badging (decal) prior to performing this test
Run generator under normal operation with no CO module notifications for a minimum of 65 seconds
With generator running, insert blunt end of a 3/64 inch drill bit into test switch hole
Hold the drill bit against the mounting panel until notification LEDs appear and generator shuts off
Successful pin test shows both LEDs on solid (not blinking)

Test 49 – Test Recoil Function diagnostic

Attempt to pull start the engine and observe.
Check whether the cord pulls easily and smoothly.
Check whether the cord returns with no assistance.
Check whether the engine turns over as the cord is pulled.

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 GP8000E?

The Generac GP8000E engine has an oil capacity of 1.0 liters.

Which generators use the Generac GP8000E engine?

The Generac GP8000E powers 1 generator set(s), including Generac GP8000.

How often should you change the oil in the Generac GP8000E?

The Generac GP8000E oil change interval is every 100 hours.

What is a common problem with the Generac GP8000E engine?

A commonly reported issue on generators using the Generac GP8000E is: Recoil Cord Will Not Pull. Cause: BAD. Fix: TEST 49 – TEST RECOIL FUNCTION TEST 50 – TEST ENGINE FUNCTION REPAIR OR REPLACE.