Case 1840 Skid Steer Starting Problems and Fuel System Diagnosis

[MikePhua]

The Case 1840 and Its Enduring Popularity
The Case 1840 skid steer loader, introduced in the early 1990s, became one of Case Construction’s most successful compact machines. Built in Wichita, Kansas, the 1840 was part of a lineage that helped Case dominate the skid steer market throughout the decade. With over 60,000 units sold globally, the 1840 earned a reputation for mechanical simplicity, rugged construction, and ease of maintenance. Powered by a naturally aspirated 51-horsepower Cummins 4B diesel engine, it remains a staple on farms, construction sites, and rental fleets.
Despite its reliability, aging units often develop intermittent starting issues—especially in cold climates or after long idle periods. These problems are usually rooted in fuel delivery, electrical connections, or solenoid failure.
Symptoms of Erratic Starting and Engine Surging
A common failure pattern begins with the engine revving erratically—cycling between high and low RPMs—before stalling completely. After shutdown, the machine refuses to restart, even with fresh fuel added. This behavior suggests a disruption in fuel delivery or solenoid control, rather than a mechanical fault.
In one case, the operator suspected air in the fuel lines and manually bled the system by cracking each injector fitting. Diesel flowed freely, but the engine remained unresponsive. After replacing the lift pump, the machine started and ran for over an hour under load—only to repeat the same failure cycle. This points to a deeper issue, possibly thermal or electrical in nature.
Fuel System Components and Troubleshooting Steps
The Case 1840 uses a mechanical lift pump to draw fuel from the tank to the injection pump. Key components include:

• Fuel tank with breather cap
  
• Lift pump (mechanical diaphragm type)
  
• Inline fuel filter
  
• Injection pump with fuel shutoff solenoid
  
• Return lines and injector fittings
  

To diagnose fuel-related issues, follow these steps:

• Check the fuel tank breather. A blocked vent can create vacuum pressure, starving the pump. Try running the machine with the cap removed.
  
• Inspect fuel lines for debris, rust flakes, or collapsed elbows. Replace any soft or kinked hoses.
  
• Drain the fuel tank using the bottom plug and inspect for water, sludge, or foreign objects.
  
• Bypass the tank by feeding clean diesel from a temporary container directly to the lift pump.
  
• Replace the fuel filter and prime the system thoroughly using the manual lever on the lift pump.
  

One operator discovered a plastic earplug lodged in the pickup tube, intermittently blocking flow. Another found that the fuel cap’s breather was clogged with dust, causing vapor lock during warm operation.
Solenoid Failure and Electrical Remedies
The fuel shutoff solenoid is a known weak point in older 1840s. It controls fuel delivery to the injection pump and is activated by the ignition circuit. Symptoms of failure include:

• Engine starts cold but dies after warming up
  
• No clicking sound from solenoid during key-on
  
• Loose or corroded spade connectors
  
• Coil failure due to heat soak
  

To test and bypass the solenoid:

• Remove the retaining screw and inspect the plunger and spring
  
• Reinstall the solenoid body without the plunger to allow fuel flow
  
• Use the manual shutoff lever on top of the injection pump to stop the engine
  
• Replace the spade connector with a crimped ring terminal for better contact
  

In one field repair, a technician soldered a loop terminal directly to the solenoid wire and secured it with the original screw, eliminating intermittent contact. This fix restored consistent operation until a new solenoid could be sourced.
Cold Weather Considerations and Fuel Treatment
Winter operation introduces additional variables. Diesel fuel can gel or separate, especially if untreated. The operator in this case used K100 fuel additive, which helps stabilize diesel and disperse water. However, additives cannot compensate for clogged filters or failing pumps.
Recommendations for cold weather prep:

• Use winter-grade diesel or add anti-gel treatment
  
• Replace fuel filters before the season begins
  
• Keep the tank full to reduce condensation
  
• Install a block heater or battery warmer if available
  
• Inspect glow plugs and timer circuits in cold-start models
  

Preventive Maintenance and Long-Term Solutions
To avoid recurring starting issues, implement a preventive maintenance schedule:

• Drain and flush the fuel tank annually
  
• Replace lift pump every 1,000 hours or as needed
  
• Inspect solenoid wiring and connectors quarterly
  
• Clean breather cap and vent lines
  
• Keep a spare fuel filter and solenoid on hand
  

Fleet managers should consider retrofitting older 1840s with upgraded electrical harnesses and modern fuel pumps. These upgrades improve reliability and reduce downtime, especially in rental or high-use environments.
Conclusion
The Case 1840 skid steer remains a workhorse decades after its release, but starting issues can arise from overlooked fuel and electrical components. By understanding the machine’s fuel system, diagnosing solenoid behavior, and applying field-tested solutions, operators can restore performance and extend service life. Whether clearing snow in Ontario or grading driveways in Kansas, the 1840 proves that good design and smart maintenance still move dirt.