Diagnosing Electrical Failures in a Woodchuck WC17 with Ford LRG-425 Engine

[MikePhua]

The Woodchuck WC17 and Ford LRG-425 Powertrain Pairing
The Woodchuck WC17 is a mid-sized industrial wood chipper designed for municipal and commercial tree service operations. Built for reliability and ease of service, it often came equipped with the Ford LRG-425 2.5L inline-four gas engine—a robust, emissions-compliant industrial powerplant used in generators, forklifts, and stationary equipment throughout the 1990s and early 2000s.
The LRG-425 engine, manufactured by Ford Power Products, features electronic ignition, a cogged timing belt driving both the camshaft and oil pump, and a closed crankcase ventilation system. Its industrial variant includes an Engine Protection Module (EPM), which monitors oil pressure, coolant temperature, and other critical parameters to prevent engine damage. When paired with the WC17, this engine provides smooth torque delivery and consistent performance under variable chip loads.
Symptoms of Electrical Failure and EPM Lockout
A common issue encountered in aging WC17 units is engine shutdown immediately after startup, often accompanied by a failure to crank unless the starter solenoid is manually jumped. In many cases, the engine will run for only a few seconds before shutting down again, and will only restart after cycling the ignition key.
These symptoms typically point to one or more of the following:

• EPM lockout due to missing or invalid sensor input
  
• No signal from the oil pressure sender
  
• Faulty or disconnected wiring on the downstream side of the oil gauge
  
• Starter solenoid not receiving proper voltage from the ignition circuit
  
• EPM controller failure or missing pinout configuration
  

The Ford LRG-425’s EPM is designed to shut down the engine if oil pressure is not detected within seconds of startup. If the oil sender wire is missing or disconnected, the EPM interprets this as a loss of pressure and cuts ignition. Similarly, if the oil gauge is not wired correctly, the signal loop may be broken, triggering a false shutdown.
A technician in Michigan encountered this issue on a WC17 and traced it to a missing wire between the oil sender and the EPM input. After installing a new sender and verifying continuity, the engine ran normally without manual solenoid intervention.
Understanding the EPM and Wiring Architecture
The EPM controller is a solid-state module that interfaces with:

• Oil pressure sender
  
• Coolant temperature sensor
  
• Ignition switch
  
• Starter solenoid
  
• Fuel shutoff solenoid
  
• Ground and battery power
  

Its logic is simple: if oil pressure and coolant temperature are within safe limits, the EPM allows ignition and fuel delivery. If either parameter fails, it disables the system to prevent engine damage.
Typical wiring layout includes:

• Ignition switch to EPM power input
  
• EPM output to starter solenoid trigger
  
• Oil sender to EPM sensor input
  
• Ground from EPM to engine block
  
• Fuel solenoid energized via EPM relay
  

Without a wiring diagram, diagnosing faults becomes difficult. The EPM’s pinout varies by model year and supplier, and some units lack visible part numbers. Engine Distributors Inc. (EDI), a known supplier of Ford industrial engines, offers updated EPM kits—but at a cost exceeding $3,000, including installation.
Field Repair Strategies and Workarounds
For technicians working without a diagram, here are practical steps:

• Trace all wires from the ignition switch to the starter solenoid and EPM
  
• Verify oil sender connection and test for resistance or voltage output
  
• Check for continuity between oil sender and EPM input pin
  
• Inspect ground connections for corrosion or looseness
  
• Test starter solenoid voltage during key-on and crank cycles
  
• Bypass EPM temporarily for diagnostic purposes only (not recommended for long-term use)
  

In Alberta, a chipper operator bypassed the EPM by wiring the starter solenoid directly to the ignition switch. While this allowed the engine to run, it disabled protection features and led to a seized engine after an unnoticed oil leak. The lesson: bypass only for testing, never for operation.
Recommendations for Long-Term Reliability
To restore full functionality:

• Source a wiring diagram from Ford Power Products or EDI
  
• Replace missing or damaged oil sender and verify gauge wiring
  
• Install a new EPM with documented pinout if original is unserviceable
  
• Label all wires during disassembly to aid future troubleshooting
  
• Add a diagnostic LED or buzzer to indicate EPM shutdown events
  

A fleet manager in Florida retrofitted his WC17 units with aftermarket engine monitors that displayed oil pressure and temperature in real time. This reduced false shutdowns and improved operator awareness.
Conclusion
Electrical issues in the Woodchuck WC17 with Ford LRG-425 engines often stem from missing or miswired oil pressure circuits and EPM controller faults. With careful tracing, sensor verification, and proper documentation, these problems can be resolved without resorting to costly controller replacements. In machines built for rugged service, a few wires can make the difference between downtime and dependable performance.