Field Diagnostics and Engine Behavior in the Genie GTH-844 with Perkins Power

[MikePhua]

The Genie GTH-844 and Its Telehandler Legacy
The Genie GTH-844 is a widely used rough-terrain telehandler designed for lifting, placing, and transporting materials in construction, agriculture, and industrial settings. With a maximum lift capacity of 8,000 pounds and a reach height of 44 feet, it balances power and maneuverability. Genie, a subsidiary of Terex Corporation, introduced the GTH series in the early 2000s, and the 844 quickly became a staple in rental fleets and contractor yards across North America.
Many GTH-844 units are powered by Perkins diesel engines—typically the 1104C or 1104D series. These four-cylinder, naturally aspirated or turbocharged engines are known for their fuel efficiency, mechanical simplicity, and global parts availability. Perkins, founded in 1932 in the UK, has supplied engines to dozens of OEMs and remains a trusted name in off-highway powerplants.
Terminology Annotation

• Telehandler: A telescopic handler or boom lift vehicle used for material placement at height or distance.
  
• Perkins 1104 Series: A family of 4.4-liter diesel engines used in industrial and agricultural equipment.
  
• Fuel Shutoff Solenoid: An electrically actuated valve that controls fuel delivery to the injection pump.
  
• Glow Plug Relay: A control device that energizes glow plugs for cold starting assistance.
  

Common Engine Behavior and Starting Challenges
Operators of the GTH-844 with Perkins engines occasionally report issues such as:

• Engine cranking but not starting
  
• Fuel solenoid clicking but no fuel delivery
  
• Glow plug relay not engaging
  
• Engine starting only with manual override or direct wire jump
  

These symptoms often point to electrical faults in the ignition circuit, fuel solenoid, or safety interlocks. In one field case, a technician found that the engine would only start when the fuel solenoid was manually energized with a jumper wire—indicating a failed relay or broken wire in the control harness.
Electrical System and Solenoid Control
The fuel shutoff solenoid is a critical component. When energized, it allows fuel to flow to the injection pump. If the solenoid fails or receives no voltage, the engine will crank endlessly without firing.
Diagnostic steps:

• Check voltage at the solenoid terminal during key-on and crank
  
• Inspect fuse panel for blown fuses related to engine control
  
• Test the ignition switch output with a multimeter
  
• Verify ground continuity at the solenoid mounting point
  
• Bypass the solenoid temporarily to confirm engine function
  

In some Genie units, the solenoid is controlled via a relay that also powers the glow plug circuit. A failed relay can disable both systems simultaneously.
Glow Plug System and Cold Start Behavior
Perkins engines rely on glow plugs for cold starting, especially in temperatures below 10°C. The glow plug relay should engage for 5–10 seconds before cranking, energizing the plugs to preheat the combustion chamber.
To test:

• Listen for relay click during key-on
  
• Measure voltage at each glow plug terminal
  
• Inspect relay for corrosion or heat damage
  
• Replace glow plugs if resistance exceeds manufacturer spec
  

In one Canadian jobsite, a GTH-844 failed to start on a frosty morning. The technician discovered that the glow plug relay had melted internally. Replacing it restored normal cold-start behavior.
Safety Interlocks and Control Logic
Genie telehandlers include safety interlocks that prevent engine start or boom movement unless certain conditions are met. These may include:

• Neutral gear position
  
• Seat switch engagement
  
• Parking brake applied
  
• Boom fully retracted
  

If any of these sensors fail or miscommunicate, the ECU may block fuel solenoid activation. Technicians should inspect each switch and confirm continuity. In some cases, bypassing the seat switch temporarily can help isolate the fault.
Preventative Measures and Upgrade Suggestions
To improve reliability:

• Replace all relays with sealed automotive-grade units
  
• Use dielectric grease on connectors exposed to moisture
  
• Install a manual override switch for the fuel solenoid in emergency scenarios
  
• Label all wires in the engine harness for easier diagnostics
  
• Add a voltmeter to the dash to monitor battery and charging health
  

In one rental fleet, adding a fuel solenoid indicator light reduced no-start service calls by 40% over six months.
Conclusion
The Genie GTH-844 telehandler with a Perkins engine is a dependable workhorse, but its starting and fuel delivery systems require careful attention—especially in older units or harsh environments. Electrical faults in the solenoid circuit, glow plug relay, or safety interlocks can mimic mechanical failure, leading to unnecessary downtime. With methodical diagnostics, upgraded components, and preventative care, technicians can keep these machines running smoothly and reliably across seasons and job sites.