What Happens When a Case 850B Runs Out of Diesel

[MikePhua]

The Case 850B Legacy
The Case 850B dozer-loader, introduced in the early 1980s, was part of Case Corporation’s push to dominate the mid-size crawler market. Case, founded in 1842 by Jerome Increase Case, had already built a reputation for durable agricultural and construction machinery. By the time the 850B was released, Case had merged with International Harvester’s construction division, further strengthening its engineering capabilities.
The 850B featured a 6-cylinder diesel engine, hydrostatic steering, and a torque converter transmission. It was designed for versatility—used in grading, land clearing, and light excavation. With thousands of units sold globally, especially in North America and Australia, the 850B became a staple on job sites due to its reliability and ease of maintenance.
Running Dry The Hidden Consequences
Running out of diesel in a machine like the Case 850B isn’t just an inconvenience—it’s a mechanical setback. Diesel engines rely on continuous fuel flow to maintain pressure in the injection system. When the tank runs dry, air infiltrates the fuel lines, filters, and injection pump, disrupting combustion.
Unlike gasoline engines, diesel systems are not self-priming. Once air enters, it must be manually purged—a process known as bleeding. Without proper bleeding, the engine will crank endlessly without firing, potentially damaging the starter motor or injection pump due to lack of lubrication.
Bleeding the Fuel System
Bleeding is the process of removing trapped air from the fuel system to restore proper pressure and flow. On the Case 850B, this involves several steps:

• Locate the hand primer pump, typically near the fuel filter housing.
  
• Replace fuel filters if the tank was run dry—sediment from the bottom may clog them.
  
• Fill the filters manually with clean diesel to reduce priming time.
  
• Open the bleed screw at the highest point of the fuel system—usually atop the filter housing.
  
• Pump the hand primer until a steady stream of fuel (no bubbles) exits the bleed screw.
  
• Tighten the bleed screw and continue pumping until resistance increases.
  
• Loosen injector line nuts one at a time while cranking the engine to confirm fuel delivery.
  
• Once fuel spurts from each line, retighten and attempt a full start.
  

This process may take several minutes, especially if the system lacks an electric lift pump. Patience is key—rushing can lead to incomplete bleeding and further frustration.
Alternative Starting Techniques
Some operators have used unconventional methods to assist starting. One involves holding a gasoline-soaked rag near the air intake while cranking. This creates a volatile vapor that encourages combustion. While effective in some cases, it carries risks:

• Gasoline vapors are flammable and can ignite unexpectedly.
  
• Prolonged cranking without fuel flow can damage the injection pump.
  
• This method bypasses proper bleeding and may mask underlying issues.
  

A safer alternative is using a diesel-compatible starting fluid, applied sparingly into the intake. However, this should only be used if the fuel system is fully primed and the engine still refuses to start.
Common Pitfalls and Misdiagnoses
Operators often overlook key issues when troubleshooting post-runout problems:

• Dirty or clogged fuel filters from sediment stirred up during tank depletion.
  
• Air locks in hard-to-reach fuel lines, especially if the machine is parked on an incline.
  
• Faulty hand primer pumps that fail to build pressure.
  
• Cracked fuel lines or loose fittings allowing air ingress.
  

In one documented case, a 1984 Case 850B stalled while climbing a steep hill with a nearly empty tank. Despite refueling and bleeding, the engine refused to start. The culprit? A missing lift pump and insufficient gravity feed. Only after force-feeding diesel through the lines did the engine fire up.
Preventative Measures
To avoid fuel starvation and its consequences, operators should adopt the following practices:

• Never allow the tank to drop below 25% capacity.
  
• Replace fuel filters every 250 operating hours or sooner if contamination is suspected.
  
• Inspect fuel lines and fittings monthly for leaks or wear.
  
• Install a low-fuel warning system if not factory-equipped.
  
• Keep a hand primer and spare filters on board for field emergencies.
  

Historical Anecdote
During the 1980s, a Canadian logging crew relied on a fleet of Case 850Bs for trail clearing. One winter, a machine ran dry in sub-zero temperatures. With no access to heated fuel or tools, the crew resorted to siphoning diesel from another dozer and warming it over a campfire before priming the system. The machine started after two hours of bleeding and cranking—a testament to both the resilience of the 850B and the ingenuity of its operators.
Modern Comparisons
Today’s diesel machines often include electric lift pumps, automatic priming systems, and onboard diagnostics. Yet, older models like the Case 850B remain in service due to their mechanical simplicity and robust design. Understanding their quirks—like manual bleeding—is essential for keeping them operational.
Final Thoughts
Running out of fuel in a Case 850B is more than a minor hiccup—it’s a lesson in diesel mechanics. With proper technique, patience, and preventative care, operators can restore function and avoid long-term damage. The 850B may be a relic of the past, but its legacy lives on in the hands of those who know how to coax it back to life.