Case 1840 Skid Steer Fuel Issue Explained

[MikePhua]

Overview of the Case 1840
The Case 1840 is a compact skid steer loader produced by Case Construction Equipment. According to its specs, it has around 54 hp at 2,000 rpm from a 4.0 L (390 ci) diesel engine.  Its hydrostatic drive provides 15.3 gal/min (≈ 57.9 L/min) at a system pressure of 2,300 psi.  Operating weight is about 5,558 lb (≈ 2.48 t).

Reported Fuel‑System Problem
A user reported that their 1840 would not reliably start or run:

• It started once using ether, ran about 15 minutes, then shut off, and would not start again.
  
• During priming, the manual lever pumps stiffly for 5–7 strokes, then “goes limp,” and after pausing 20 seconds, the cycle repeats.
  
• The supply line from the tank “holds suction” when tested by mouth, indicating the lift pump may draw fuel correctly.
  
• There are no obvious fuel leaks around filters or lines.
  
• After replacing filters and fuel line, the problem persisted, suggesting deeper fuel-system or pump issues.
  

Expert Analysis and Diagnostics
Several experienced users and a professional injection-pump rebuilder weighed in. Key points and insights include:

• The lift‑pump (also called transfer or primer pump) may be a diaphragm-style pump. One expert explained that once the pump chamber reaches vacuum and begins to flow, the lever resistance drops because the diaphragm moves away from the lever.
  
• When bleeding the system, a proper test is to loosen the bleeder screw by the nameplate on the injection pump, pump until fuel squirts out, then start the engine with all injector lines loosened. If fuel is flowing properly, the engine should fire.
  
• If, however, there is no spray or flow during bleeding with the filters full and the high‑prime lever working, the high-pressure pump inside the injection pump may be failing.
  
• The high-pressure (HP) pump within the injection pump can both suck fuel and pressurize — meaning it may partially feed itself once running, masking a bad lift pump or supply issue.
  
• There is a cold-start solenoid (wax motor) on some injection pumps of this model. This solenoid advances or retards timing based on temperature; if it’s broken or stuck, it may affect starting.
  
• Electrical issues may also be involved: a user measured 12 V at the solenoid when the key is on, but only ~1 V during cranking, suggesting a possible ground or wiring problem.
  

Suggested Troubleshooting Steps
Based on the diagnostic discussion, here’s a structured approach to fix or isolate the issue:

1. Bleed the Pump Correctly
   • Use the bleeder screw on the injection pump (nameplate location) while pumping.
     
   • Confirm strong, steady fuel flow when the bleeder is open, and that the prime lever stays firm.
     
2. Check the Cold-Start Solenoid
   • Disconnect and apply correct voltage (12 V or 24 V depending on model) to test its movement.
     
   • Observe if the plunger moves slowly over several minutes (normal behavior: 3–5 minutes).
     
   • If it’s stuck in the wrong position, this could impact fuel timing and starting behavior.
     
3. Test Injector Lines During Cranking
   • With the engine cranking, loosen all injector lines at the pump.
     
   • Fuel should spray out as the engine turns, indicating the high-pressure pump is building pressure.
     
4. Verify Electrical Supply
   • Check for consistent 12 V to the solenoid during cranking (not just when the ignition is “On”).
     
   • Test for ground problems if voltage drops during cranking.
     
   • Try jumping the solenoid directly from the battery to see if the engine starts (with caution).
     
5. Inspect Fuel Lines and Filters
   • Confirm that new filters have correct sealing O-rings; missing or double O-rings can introduce air.
     
   • Blow out the supply line to the lift pump to ensure no blockage or debris.
     
   • Check for air bubbles in return lines, which may indicate a leak or bad fitting.
     

Real-World Example
One user replaced the filters and lift pump, but still couldn’t start. The expert rebuilder suggested that the injection pump may have an internal supply pump, and when the lift pump fails, the injection pump partially feeds itself — giving the illusion the system works once started. Diagnosing this required bleeding the injector pump with loosened lines and verifying consistent fuel flow.

Risks and Considerations

• Replacing the high-pressure pump is expensive; first thoroughly rule out simpler issues like air leaks, bad filters, or faulty solenoids.
  
• If the cold-start solenoid is damaged, incorrect timing might cause poor cranking behavior or even engine damage.
  
• Always purge air from the fuel system carefully to avoid cavitation or damage to the injection pump.
  

Conclusion
The fuel‑system issue on a Case 1840 skid steer loader often traces back to air ingress, faulty priming, or a malfunctioning cold-start solenoid. Proper bleeding via the correct injector-pump bleeder, verifying consistent fuel flow, and checking the electrical components associated with the injection system are critical steps. While the high-pressure pump could be the culprit, experts strongly recommend exhausting simpler possibilities first. With systematic diagnosis and correct priming, many of these fuel issues can be fixed without a full injection-pump rebuild.