Generac V-type 6.8L Engine
The Generac V-type 6.8L is a 6.8 L naturally aspirated engine. It powers generator sets from Generac, including the V-10 6.8L.
Also known as: Generac V-type 6.8L
Engine specifications
| Displacement | 6.8 L |
|---|
| Aspiration | Naturally Aspirated |
|---|
Common problems
7- No AC output from generator.
Cause: Check main line circuit breaker; Check circuit breaker & fuses; Transfer switch set to NORMAL position; Generator internal failure; Thermal circuit breaker open
Fix: 1. Reset to ON or CLOSED; 2. Reset and replace, if necessary; 3. Set to GENERATOR position; 4. *; 5. Auto-reset - Wait 5 min. and attempt restart - Fuel System Fault FuelSys006
- Engine won’t crank.
Cause: 15 amp fuse blown; Loose or corroded or defective battery cables; Defective starter contactor; Defective starter motor; Dead or Defective Battery; 5 amp fuse blown
Fix: 1. Replace fuse; 2. Tighten, clean or replace battery cables as necessary; 3. Replace contactor; 4. Replace starter motor; 5. Remove, change or replace battery - Engine starts then shuts down.
Cause: Engine oil level is low; Engine is overheated; Defective Low Oil Pressure Switch; Defective Coolant Temperature Switch; Defective Control Module circuit board; Coolant Level is Low; Defective Low Coolant Level Switch
Fix: 1. Check oil and add oil as needed; 2. Check cooling system for leaks; 3. Replace switch; 4. Replace switch; 5. Replace board; 6. Repair leak - Add coolant; 7. Replace Switch - Engine starts hard, runs rough.
Cause: Flame arrestor (air cleaner) plugged or damaged; Plugged fuel line; Defective spark plugs; Fuel pressure incorrect
Fix: 1. Clean or replace as needed; 2. Unclog fuel line; 3. Clean, regap or replace plugs; 4. Confirm fuel pressure to regulator is as recommended in SPECIFICATIONS - Engine cranks but won't start.
Cause: Out of fuel; Fuel solenoid (FS) is defective; Open Wire #14A from Engine Control circuit board; Spark plugs defective; Door on tank not closed
Fix: 1. Replenish fuel; 2. Replace solenoid; 3. Reconnect wire; 4. Clean, regap or replace plugs; 5. Close door on tank - AUTO/OFF/MANUAL Switch at OFF, engine continues to run.
Cause: Defective AUTO/OFF/MANUAL switch; Open/disconnected wire #15A between AUTO/OFF/MANUAL switch and Control Module circuit board; Defective Control Module circuit board
Fix: 1. Replace switch; 2. Reconnect/close wire; 3. Replace board
Compiled from service & troubleshooting documentation across every generator set that uses the Generac V-type 6.8L.
Service intervals
18| Item | Action | Hours | Months | Notes |
|---|
| Engine oil level | Check | 10 hr | 1 mo | At least every 20 hours of operation or prior to use |
| Engine break-in oil and filter | Change | 30 hr | | First service — First 30 operating hours |
| Engine oil and oil filter | Change | 100 hr | | First service — First 100 operating hours; thereafter every 150 hours or 6 months |
| Air cleaner | Clean | 500 hr | | Service air cleaner |
| Engine DC alternator | Check | 500 hr | | |
| Starter | Check | 500 hr | | |
| Battery state of charge and condition | Check | | 3 mo | Performed by authorized service dealer |
| Cooling system | Drain | | 12 mo | Flush cooling system |
| Cooling system | Inspect | | 1 mo | At least once each month |
| Engine governor | Test | | 12 mo | Adjust or repair if needed |
| Engine ignition system | Check | | 3 mo | |
| Engine safety devices (low oil pressure, low coolant level, high coolant temperature) | Test | | 6 mo | |
| Exhaust system | Inspect | | 3 mo | |
| Fan belts | Check | | 3 mo | |
| Fuel system | Test | | 3 mo | |
| Generator | Clean | | 12 mo | Clean, inspect generator |
| Spark plugs | Clean | | 12 mo | Clean/re-gap or replace as necessary |
| Transfer switch | Check | | 3 mo | |
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
4| Type | Item | Value | Unit | Condition |
|---|
| Gap | Spark plug gap | 1.14 | mm (0.045 inch) | |
| Other | Belt tension deflection (midway between pulleys) | 3/8 to 5/8 | inch (10 to 16 mm) | 22 pounds (10 kg) force |
| Speed | Engine timing BTDC at 1800 rpm (6.8L NG/LP) | 22 | degrees | 1800 rpm |
| Speed | Engine timing BTDC at 3600 rpm (6.8L NG/LP) | 24 | degrees | 3600 rpm |
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 |
|---|
| Coolant | 50-50 low silicate ethylene glycol base anti-freeze and deionized water | Low silicate anti-freeze | | 4.5 U.S. gal. | Add high quality rust inhibitor if desired |
| Engine oil | 5W-20 (factory fill); 5W-30 | For Service SJ or SH | | 5.0 U.S. qts. | Use 5W-30 synthetic oil below 32°F |
| Fuel | Natural gas at least 1,000 Btu/cu ft; LP gas at least 2,520 Btu/cu ft | | | | Operating fuel pressure 11 in. - 14 in. water column |
| Gear oil | SAE 90 gear lubricant | | | | For generator gearbox (if equipped) |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Procedures
8Spark Plugs adjustment
⚠ Do not blast the spark plugs to clean.
Tools: wire feeler gauge, wire brush
- Clean the area around the base of the spark plugs.
- Remove the spark plugs and check the condition. Replace if worn.
- Check the spark plug gap using a wire feeler gauge. Adjust gap to 1.14 mm (0.045 inch).
Catalyst and Heat Shield Assembly installation
⚠ Catalyst must be mounted in described position.
- Disconnect battery cables; disconnect negative first.
- Insert outlet pipe 2 to 3 inches into outlet of catalyst; slide one U-bolt onto outlet and tighten.
- Slide remaining U-bolt and catalyst over exhaust pipe; insert 2 to 3 inches into inlet; align flat side; tighten U-bolt.
- Sub-assemble heat shield panels and cap using screws provided.
- Slide heat shield subassembly over the catalyst.
- Fasten heat shield assembly to enclosure using screws provided.
- Install rain cap over outlet of catalyst and tighten.
Preparation for Start-up (Start-up Checklist) installation
Tools: manometer
- Ensure the 120VAC circuit breaker to the battery charger is open.
- Remove the 15 Amp ATO fuse from the control panel.
- Connect the battery cables to the battery; attach negative cable last.
- Close the 120VAC circuit breaker to the battery charger.
- Measure battery voltage before and after charger is turned on.
- Verify all AC electrical connections are tight.
- Check all hoses, clamps, fittings for leaks or damage.
- Open the valve to the engine fuel line and bleed the fuel system of air.
- Open the generator main line circuit breaker.
- Connect a manometer to the gas line and record static pressure.
- Insert the fuse into the control panel.
- Move the AUTO/OFF/MANUAL switch to manual; engine should crank and start.
- Check voltage at the generator terminals and phase rotation for 3-phase units.
- Close the generator main line circuit breaker and turn the set off.
Battery Maintenance maintenance
⚠ Storage batteries give off explosive hydrogen gas.
⚠ Battery electrolyte fluid is an extremely caustic sulfuric acid solution.
⚠ Do not use any jumper cables or booster battery to crank and start the generator engine.
Tools: automotive-type battery hydrometer
- Inspect the battery posts and cables for tightness and corrosion. Tighten and clean as necessary.
- Check the battery fluid level of unsealed batteries and fill with DISTILLED WATER ONLY.
- Have the state of charge and condition checked with an automotive-type battery hydrometer.
Changing Engine Oil maintenance
⚠ Hot oil may cause burns. Allow engine to cool before draining oil.
⚠ NEVER OPERATE ENGINE WITH OIL BELOW THE DIPSTICK ADD MARK.
- Remove OIL DRAIN HOSE from its retaining clip.
- Loosen and remove OIL DRAIN HOSE CAP. Drain oil completely into suitable container.
- Install and tighten OIL DRAIN HOSE CAP, re-install into its retaining clip.
- Turn OIL FILTER counterclockwise and remove. Dispose of old filter.
- Apply light coating of new engine oil to seal of new oil filter. Install and tighten by hand only.
- Remove OIL FILL CAP. Add recommended oil. Do not fill above dipstick FULL mark.
- Start engine and check for oil leaks.
- Shut OFF engine and wait 10 minutes for oil to settle. Recheck oil level.
- Dispose of used oil at a proper collection center.
Changing the Engine Air Cleaner maintenance
- Remove the air cleaner cover.
- Replace the air filter making sure it is positioned properly before reattaching the cover.
Engine Start-up and Transfer operation
⚠ Do not crank the engine continuously for longer than 30 seconds.
- Turn OFF or disconnect the utility power circuit to the transfer switch.
- Set the transfer handle to its UTILITY (NORMAL) position.
- Set the generator's main line circuit breaker to its OFF position.
- Start the generator.
- Let engine stabilize and warm up.
- Check all applicable instrument and gauge readings.
- Move the transfer switch manual handle to STANDBY position.
- Set the generator's main line circuit breaker to its ON position.
Retransfer and Shutdown operation
- Set the generator's main line circuit breaker to its OFF position.
- Manually move the transfer switch handle to its UTILITY (NORMAL) position.
- Turn ON the utility power supply to the transfer switch.
- Let the generator run at no-load for a few minutes to stabilize internal temperatures.
- Shut down the generator.
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 |
|---|
| 120/208V | 3 | Stator Power Winding Connections - 3-phase, Y configuration | 6 | L-L 208V; L-N 120V |
| 120/240V | 3 | Stator Power Winding Connections - 3-phase, Delta configuration | 6 | Rated voltage E1-E2, E1-E3, E2-E3 is 240V; E1 or E3 to neutral 00 is 120V |
| 240V | 1 | Four-lead, Single-phase Stator (voltage code A) | 4 | Rated voltage between terminals 240V; terminal to neutral 00 is 120V |
| 277/480V | 3 | Stator Power Winding Connections - 3-phase, Y configuration | 6 | L-L 480V; L-N 277V |
| 346/600V | 3 | Stator Power Winding Connections - 3-phase, Y configuration | 6 | L-N 346V |
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 displacement of the Generac V-type 6.8L?
The Generac V-type 6.8L has a displacement of 6.8 liters.
Which generators use the Generac V-type 6.8L engine?
The Generac V-type 6.8L powers 1 generator set(s), including Generac V-10 6.8L.
What is a common problem with the Generac V-type 6.8L engine?
A commonly reported issue on generators using the Generac V-type 6.8L is: No AC output from generator.. Cause: Check main line circuit breaker; Check circuit breaker & fuses; Transfer switch set to NORMAL position; Generator internal failure; Thermal circuit breaker open. Fix: 1. Reset to ON or CLOSED; 2. Reset and replace, if necessary; 3. Set to GENERATOR position; 4. *; 5. Auto-reset - Wait 5 min. and attempt restart.