Bobcat 743B Starting Issues and the Anatomy of Cold Crank Troubleshooting

[MikePhua]

The Bobcat 743B and Its Role in Compact Equipment History
The Bobcat 743B skid steer loader was introduced in the late 1980s as part of Bobcat’s 700-series evolution, designed to offer reliable performance in a compact footprint. Powered by a 36-horsepower Kubota V1702 diesel engine, the 743B featured a hydrostatic transmission, mechanical lift arms, and a straightforward electrical system. It quickly became a favorite among landscapers, small contractors, and rental yards due to its simplicity and ease of maintenance.
Bobcat, founded in North Dakota in the 1950s, pioneered the skid steer concept and has sold millions of units globally. The 743B was one of the transitional models bridging early mechanical designs with more refined hydraulic and electrical systems. Its popularity ensured a long service life, but as these machines age, starting problems become increasingly common.
Terminology annotation:

• Hydrostatic transmission: A drive system using hydraulic fluid to transfer power from the engine to the wheels, allowing smooth variable-speed control.
  
• V1702 engine: A four-cylinder Kubota diesel engine known for reliability but sensitive to fuel and electrical conditions.
  

In a snow removal crew in Wisconsin, a 743B refused to start after sitting idle for two weeks. The issue was traced to a weak ground connection and a corroded glow plug relay.
Common Starting Failures and Diagnostic Pathways
Starting problems in the 743B typically fall into three categories: electrical faults, fuel delivery issues, and mechanical wear. Diagnosing the root cause requires a systematic approach.
Electrical faults:

• Weak or dead battery
  
• Corroded terminals or ground strap
  
• Faulty starter solenoid or ignition switch
  
• Glow plug circuit failure
  
• Loose or damaged wiring harness
  

Fuel delivery issues:

• Air in fuel lines due to leak or filter change
  
• Clogged fuel filter or sediment bowl
  
• Weak lift pump or injector malfunction
  
• Water contamination in diesel
  
• Fuel shutoff solenoid not engaging
  

Mechanical wear:

• Low compression due to worn rings or valves
  
• Sticking valves or carbon buildup
  
• Starter motor dragging under load
  
• Cold-weather oil viscosity too high
  

Terminology annotation:

• Glow plug: A heating element used to warm diesel engine cylinders for easier cold starts.
  
• Solenoid: An electromechanical device that controls the flow of current or fluid, often used in starter and fuel systems.
  

In a grading job in Alberta, a 743B failed to crank despite a new battery. The starter solenoid was receiving voltage but not engaging. Replacing the solenoid resolved the issue immediately.
Step-by-Step Troubleshooting Strategy
To isolate the problem, technicians should follow a structured diagnostic sequence:

1. Check battery voltage (should be 12.6V or higher at rest)
   
2. Inspect terminals and ground strap for corrosion or looseness
   
3. Test glow plug circuit with multimeter (resistance and voltage)
   
4. Listen for fuel solenoid click when key is turned
   
5. Crack injector line to check for fuel delivery during cranking
   
6. Remove air filter and check for intake blockage
   
7. Use starter bypass method to test solenoid engagement
   
8. Perform compression test if cranking is strong but engine won’t fire
   

Recommended tools:

• Multimeter with continuity and voltage settings
  
• Fuel pressure gauge or visual injector test
  
• Compression tester for diesel engines
  
• Remote starter switch or jumper wire
  
• Infrared thermometer for glow plug heat verification
  

Terminology annotation:

• Starter bypass method: A technique using a jumper wire to engage the starter directly, bypassing the ignition circuit.
  
• Compression test: A diagnostic procedure measuring cylinder pressure during cranking to assess engine health.
  

In a rental yard in Texas, a 743B showed intermittent starting. The glow plug relay was clicking but not delivering voltage. Replacing the relay restored cold-start reliability.
Preventative Maintenance and Cold Start Optimization
To reduce starting issues, especially in cold climates or seasonal use, preventative care is essential.
Best practices:

• Replace fuel filters every 250 hours or annually
  
• Use winter-grade diesel or anti-gel additives
  
• Clean battery terminals monthly
  
• Test glow plugs before winter season
  
• Store machine with full fuel tank to reduce condensation
  
• Use block heater or intake heater in sub-zero conditions
  

Suggested upgrades:

• Install LED battery voltage monitor
  
• Add manual fuel primer pump for air purging
  
• Replace starter with high-torque aftermarket unit
  
• Use synthetic engine oil for better cold flow
  
• Add relay bypass switch for emergency starts
  

Terminology annotation:

• Anti-gel additive: A chemical added to diesel fuel to prevent wax crystals from forming in cold temperatures.
  
• Block heater: An electric heating element installed in the engine block to warm coolant and aid cold starts.
  

In a landscaping fleet in Maine, switching to synthetic oil and installing a block heater reduced starting complaints by 80% during winter months.
Conclusion
Starting problems in the Bobcat 743B are often rooted in simple faults—corroded terminals, weak batteries, or fuel delivery hiccups. But diagnosing them requires patience, precision, and a clear understanding of the machine’s systems. With proper maintenance and a few strategic upgrades, even a decades-old 743B can fire up reliably and keep pushing dirt like it did the day it rolled off the line. In the world of compact loaders, starting is more than ignition—it’s confidence.