Description
Hard-Numbers: Technical Specifications
- Rated Voltage: 24 VDC
- Coil Resistance: 7.2 ± 0.4 Ω (at 22°C / 72°F)
- Coil Inductance: 120 ± 20 mH
- Reaction Time: 15 milliseconds (typical actuation)
- Operating Temp Range: -38°C to +125°C (-36°F to +257°F)
- Terminal Resistance @ 125°C: 10.6 Ω (max)
- Terminal Resistance @ -38°C: 7.7 Ω (min)
- Physical Weight: 0.945 kg (2.08 lbs)
- Duty Cycle: 100% Continuous
Woodward 9907-151
The Real-World Problem It Solves
When a Cummins diesel overspeeds or loses oil pressure, you need the fuel cut off instantly. The 3408324 mounts directly onto the PT (Pressure-Time) fuel pump and acts as the electronic gatekeeper. It takes a 24-volt signal from the generator’s control module (ECM) and physically gates the fuel pressure to the injectors.
Where you’ll typically find it:
- Bolted to the side of Cummins PT fuel pumps on large stationary generator sets (NTA855, K19, K38, K50).
- Integrated into the fuel systems of mining haul trucks (like BelAZ) and heavy construction equipment (like Shantui dozers).
Bottom line: It provides the fast-acting, reliable fuel cutoff necessary to protect your prime movers from catastrophic overspeed or uncontrolled operation.
Hardware Architecture & Under-the-Hood Logic
The 3408324 is a direct-acting, pull-type electromagnetic actuator designed specifically for the harsh vibrational environment of a running diesel engine. It translates a simple 24VDC electrical signal into immediate mechanical action within the PT fuel pump.
- De-energized State (Fail-Safe): When 24VDC is removed (either intentionally for shutdown or due to a system fault), the internal stainless steel return spring forces the plunger down, physically blocking the fuel passage in the PT pump.
- Energized State (Run): When the ECM applies 24VDC to the coil, the resulting magnetic field overcomes the spring tension, pulling the iron core (plunger) up into the coil winding.
- Fuel Metering: As the plunger lifts, it opens the fuel bypass valve inside the PT pump, allowing high-pressure fuel to flow to the injectors based on the ECM’s pulse-width modulated (PWM) signal.
- Continuous Hold: The coil maintains a strong magnetic field to keep the valve open against the fuel pressure, ensuring stable engine speed and power output.
Field Service Pitfalls: What Rookies Get Wrong
Ignoring the O-Ring During Reinstallation
The 3408324 sits in a machined bore on the PT pump filled with diesel fuel. Rookies often reuse the old, flattened O-ring or forget to lubricate a new one during installation. This leads to immediate fuel leaks and potential contamination of the actuator’s electrical connector.
Field Rule: Always use a fresh Viton O-ring (and a dab of clean diesel fuel as lubricant) when installing the actuator. Torque the mounting bolts evenly in stages to the specified 25 in-lbs (2.8 N·m) to prevent warping the actuator housing.
Chasing Ghosts Caused by Dirty Fuel
A common complaint is the engine surging or failing to start even after installing a brand-new 3408324. Mechanics assume the new actuator is defective, but the real culprit is microscopic debris in the fuel system that has jammed the PT pump’s internal bypass valve.
Quick Fix: Before condemning the actuator, crack open the PT pump’s fuel inlet line and check for debris. Install a new fuel filter and flush the system. Ensure the fuel shutoff solenoid operates smoothly without the actuator installed to confirm the pump’s internal mechanism is free.
Voltage Drop on Long Cable Runs
The 3408324 requires a solid 24 volts to guarantee a crisp 15ms reaction time. Undersized wiring or poor grounds will cause the voltage to sag, resulting in a sluggish plunger movement. This manifests as a slow, lazy engine shutdown or the actuator failing to seat properly, causing a constant fuel leak.
Field Rule: Verify your control voltage directly at the actuator terminals while the engine is running. If you measure less than 23 volts, run a new dedicated 14 AWG supply wire directly from the DC busbar, ensuring a clean, low-resistance path.
Woodward 9907-151
Commercial Availability & Pricing Note
Please note: The listed price is for reference only and is not binding. Final pricing and terms are subject to negotiation based on current market conditions and availability.
