Why Is My Case 1835C TMD20 Not Getting Fuel

[MikePhua]

The Case 1835C and Its Engine Origins
The Case 1835C skid steer loader was introduced in the late 1980s as part of Case Corporation’s push into compact, high-performance construction equipment. Case, founded in 1842, had already built a reputation for durable agricultural and industrial machinery. The 1835C featured a robust design, hydrostatic transmission, and a rated operating capacity of 1,200 lbs, making it ideal for landscaping, utility work, and light excavation.
At the heart of the 1835C is the TMD20 diesel engine—a three-cylinder, indirect injection powerplant developed by Mitsubishi and adapted by Case for skid steer applications. Producing approximately 48 horsepower, the TMD20 was known for its fuel efficiency and cold-start reliability. However, as these machines aged, fuel delivery problems became increasingly common, often linked to electrical faults, pump wear, or internal contamination.
Symptoms of Fuel Delivery Failure
When the TMD20 engine fails to receive fuel, operators may observe:

• Engine cranks but does not start
  
• No fuel reaching injectors despite full tank
  
• Electric fuel pump runs but no pressure builds
  
• Fuel visible at filter and pump inlet but absent at injector lines
  
• Intermittent starting followed by stalling
  

These symptoms typically point to issues in the fuel supply chain, from the tank to the injectors, including electrical connections, solenoids, and internal pump components.
Key Components in the Fuel System
The Case 1835C fuel system includes:

• Electric fuel pump: Draws fuel from the tank and delivers it to the injection pump under low pressure.
  
• Fuel filter: Removes particulates and water from the fuel before it reaches the injection pump.
  
• Injection pump: Pressurizes and meters fuel to each injector based on engine timing.
  
• Fuel shutoff solenoid: Electrically actuated valve that allows or blocks fuel flow into the injection pump.
  
• Injector lines: High-pressure lines that deliver fuel from the pump to each cylinder.
  

Each component must function correctly for fuel to reach the combustion chamber.
Electrical Wiring and Solenoid Activation
One of the most overlooked causes of fuel starvation is improper wiring to the fuel shutoff solenoid. The solenoid requires a 12V signal from the ignition switch to open. If this wire is missing, disconnected, or corroded, the solenoid remains closed, preventing fuel from entering the pump.
In one case, a technician discovered that the solenoid wire had been mistakenly connected to a non-switched circuit. As a result, the solenoid never activated during cranking. After rerouting the wire to a key-on hot terminal, the engine started immediately.
Recommendations:

• Use a multimeter to verify voltage at the solenoid with the key on.
  
• Ensure the solenoid ground is clean and secure.
  
• Listen for a click when the key is turned—this indicates solenoid activation.
  
• Replace damaged connectors with weatherproof terminals.
  

Pump Internals and Flex Ring Failure
Another common issue involves the internal components of the injection pump. The flex ring, a rubber-like coupling inside the pump, can degrade over time due to fuel varnish and heat. When it breaks apart, debris clogs the pumping plungers, preventing fuel delivery.
In a documented rebuild, a technician found that the flex ring had disintegrated, jamming the plungers and blocking fuel flow. After cleaning the pump and replacing the ring, the engine ran smoothly. This failure is especially common in machines that sit unused for long periods, allowing fuel to oxidize and form varnish.
Signs of flex ring failure:

• No fuel at injector lines despite pump rotation
  
• Sticky or seized plungers
  
• Black residue inside pump housing
  
• Fuel pump runs but no pressure builds
  

Solutions:

• Disassemble and clean the injection pump
  
• Replace flex ring and internal seals
  
• Flush fuel lines and tank to remove debris
  
• Use fresh diesel with stabilizer additives
  

Fuel Pump and Filter Diagnostics
Even when the electric fuel pump runs, it may not deliver sufficient pressure. A clogged filter, collapsed hose, or worn pump diaphragm can restrict flow. Testing involves:

• Disconnecting the fuel line before the injection pump
  
• Turning the key to activate the pump
  
• Observing fuel flow—should be steady and strong
  
• Replacing the filter if flow is weak or intermittent
  

In one field case, a farmer replaced the fuel filter but forgot to prime the system. Air trapped in the lines prevented fuel from reaching the pump. After bleeding the system at each connection point, the engine started without issue.
Preventive Maintenance and Best Practices
To avoid fuel delivery problems on the Case 1835C:

• Replace fuel filters every 250 hours
  
• Use clean, high-quality diesel with anti-gel additives in winter
  
• Inspect wiring annually for corrosion or loose connections
  
• Prime the fuel system after filter changes
  
• Store the machine with a full tank to reduce condensation
  

Operators in colder climates often install inline heaters or use winter-grade diesel to prevent gelling. In one Alaskan municipality, a fleet manager reported that switching to heated fuel lines reduced cold-start failures by 90%.
Field Anecdotes and Lessons Learned
In rural Missouri, a contractor rebuilt his TMD20 after months of intermittent starting. He discovered that the fuel shutoff solenoid wire had been spliced with speaker wire—too thin to carry proper current. After replacing it with 14-gauge automotive wire, the solenoid clicked reliably and fuel flowed as expected.
In another case from South Africa, a mechanic found that the injection pump had been rebuilt with incorrect plunger spacing. The engine ran but misfired under load. After consulting the original service manual and resetting the timing, the machine returned to full power.
Conclusion
Fuel delivery issues in the Case 1835C TMD20 engine are often rooted in electrical faults, internal pump wear, or overlooked maintenance. By understanding the system’s components and failure modes, operators can diagnose problems efficiently and restore performance. Whether rebuilding a pump, rewiring a solenoid, or flushing varnished lines, the key is methodical troubleshooting and respect for the machine’s design. The 1835C remains a reliable workhorse, and with proper care, its diesel heart will keep beating for years to come.