Engine Failed to Fire After All Crank Attempts
What does PERKINS-OC mean?
The PERKINS-OC (Kohler RDC2) diesel fault code means: Engine Failed to Fire After All Crank Attempts. This is a serious severity code.
Common Symptoms
- Controller displays OC or Overcrank on the panel screen and the unit shuts down
- You hear the starter motor cranking repeatedly in short bursts but the engine never catches
- Generator goes through two or three crank attempts with pauses in between, then stops completely
- READY light goes out and an alarm light comes on after the crank sequence ends
- The engine may emit white or black exhaust smoke during cranking but never fully starts
- Remote monitoring systems like Mobile Link send a failed-to-start notification
- Manual restart attempts are blocked until the alarm is acknowledged and reset on the controller
Probable Causes (Ranked by Likelihood)
- Low or no fuel reaching the injectors due to empty tank, closed fuel valve, or blocked fuel filter Very Likely
- Weak or discharged battery unable to sustain starter motor speed through multiple crank cycles Very Likely
- Air in the fuel system after running dry, filter replacement, or extended storage Likely
- Faulty fuel lift pump not building enough fuel pressure to prime the injection system Likely
- Blocked or stuck fuel solenoid on the injection pump not opening to allow fuel flow Possible
- Glow plug failure preventing adequate pre-heat in cold ambient temperatures Possible
- Injection pump timing drift or internal pump fault on high-hour engines Less Likely
Step-by-Step Diagnostic Procedure
Check the fuel level gauge or physically verify the tank level. A surprising number of OC faults trace back to a tank that ran dry during a load test or extended outage. If the tank is low, refuel and bleed the system before doing anything else.
Inspect the fuel shutoff valve on the supply line between the tank and the engine. It must be fully open. Also check that the fuel solenoid on the injection pump is receiving 12V or 24V DC when the controller commands a start. Use a multimeter on the solenoid terminals during a crank attempt.
Measure battery voltage at the battery terminals while cranking. You need to see no lower than 9.6V on a 12V system or 19V on a 24V system under cranking load. If voltage drops below these numbers, the battery cannot sustain starter speed and the engine will never reach compression-ignition RPM.
Bleed the fuel system if air is suspected. Loosen the bleed screw on the primary fuel filter housing and operate the manual priming lever on the lift pump until fuel flows bubble-free. Retighten the bleed screw and repeat at the secondary filter if the engine has one. This step is required any time the engine has run dry or a fuel filter has been replaced.
Check the fuel lift pump by cracking a fuel feed line at the injection pump inlet while an assistant cranks the engine. You should see a strong, steady pulse of fuel. A weak dribble or no flow points to a failed lift pump diaphragm, which is a straightforward parts swap on most Perkins engines.
Test the glow plugs if ambient temperature is below 10 degrees C (50 degrees F). Disconnect the glow plug bus bar and measure resistance on each plug with a multimeter. A good plug reads 0.5 to 2 ohms. An open circuit or very high resistance reading means that plug is burned out and not contributing to pre-heat.
If all the above checks pass, the fault may be inside the injection pump or with the pump timing. This requires Perkins EST (Electronic Service Tool) or a qualified injection pump specialist. Do not attempt to adjust injection pump timing without the proper tools and training.
Frequently Asked Questions
What does the OC code mean on a Perkins FG Wilson generator?
OC stands for Overcrank. It means the controller commanded the starter motor to crank the engine through all of its programmed start attempts, typically two or three bursts of 10 to 15 seconds each, and the engine never fired and ran on its own. To protect the starter motor and battery from damage, the controller stopped trying and locked out further automatic start attempts until you acknowledge and reset the alarm.
Can the generator still supply power with an OC code showing?
No. The engine is not running, so there is no output. The unit is in a lockout state and will not attempt another automatic start until the fault is cleared. If you are in an active power outage, you need to identify and fix the root cause before the generator can protect your load.
How much does it cost to fix an OC overcrank fault?
It depends entirely on the root cause. If the tank ran dry and you just need to refuel and bleed the fuel system, you can fix it yourself for under $50 in materials and an hour of work. A failed battery is $150 to $300 parts. A failed lift pump or fuel filter blockage is a $200 to $500 professional service call. An injection pump failure is the worst case and can run $800 to $2,500 installed.
Will the generator start the next time the power goes out after an OC fault?
Not until the fault is cleared and the alarm is reset on the controller. After a reset, the controller will try again, but if the underlying cause is not fixed, it will crank and fail again, log another OC, and lock out a second time. Fix the root cause first, reset the alarm, then run a manual test start to confirm it fires reliably before relying on it for the next outage.