Generac G9.0L G18 Engine

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• Low output voltage
  Cause: Low engine speed
  Fix: Verify engine RPM
• Starter does not crank
  Cause: Dead battery
  Fix: Remove battery and trickle charge (do not jump start)
• Starter cranks but engine does not start
  Cause: No fuel
  Fix: Open fuel valves; purge air from fuel system; check for/repair fuel line leaks
• Output voltage fluctuates
  Cause: Irregular or fluctuating speed
  Fix: Check engine for malfunction or load for fluctuation; stabilize load—the addition of a lamp load (resistance load) may compensate partially for load changes caused by intermittent motor operation—do not overload
• Mechanical noise
  Cause: Internal failure of alternator
  Fix: Contact GMPASD
• No output voltage
  Cause: Circuit breaker tripped or failed
  Fix: Reset circuit breaker or replace if required; check electrical connections
• High output voltage
  Cause: Faulty wiring
  Fix: Check wiring
• Engine overheats
  Cause: Excessive load
  Fix: Remove one or more electrical loads
• Electrical shock when frame is touched
  Cause: Static charge
  Fix: Ground generator frame at local reference ground
• Oxygen sensor has not toggled between indicating lean and indicating rich for at least one minute — displays Malfunction Indicator Light (MIL) message CHECK ENGINE on the H-100 control panel display; does not generate audible alarms P0134
  Fix: Automatically clears after three run cycles (three times fully starting the unit and then completely shutting it down) in which no DTC conditions are active; a GMPASD can also clear the DTC through GenLink
• Engine starts but runs poorly
  Cause: Fuel or ignition problem
  Fix: Contact Generac Mobile Products Technical Service
• Engine loses frequency, stalls, or switches to LPL fuel
  Cause: Diameter of pipes is too small between fuel source and unit
  Fix: Install pipes of appropriate diameter

Compiled from service & troubleshooting documentation across every generator set that uses the Generac G9.0L G18.

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