5 hours ago
The Case 350 and Its Fuel System
The Case 350 crawler dozer, equipped with the 188 cubic inch diesel engine, was a staple in compact earthmoving during the 1970s and 1980s. Its mechanical simplicity and rugged build made it popular among small contractors and landowners. The engine’s fuel delivery system relies on a Roosa Master rotary injection pump—a compact, cam-driven unit known for its reliability and precision metering. Over time, however, these pumps suffer from internal wear, fuel contamination, and seal degradation, leading to hard starts, poor injection timing, and eventual failure.
From Rusted Core to Functional Pump
One operator undertook the challenge of rebuilding a Roosa Master pump that had been sitting in poor condition. The pump was stripped down, cleaned, and fitted with:
• A new transfer pump liner
• Fresh rotor blades
• An updated governor weight retainer
• All new O-rings and seals
The rebuild was done manually, without specialized test benches. To verify functionality, the pump was mounted in a vise and rotated using a speed wrench. Remarkably, it began drawing fuel immediately, even with minimal cranking. This indicated that the transfer pump and rotor assembly were sealing properly and generating suction.
Terminology Clarification
• Transfer Pump Liner: A sleeve inside the pump housing that guides fuel into the rotor cavity.
• Governor Weight Retainer: A component that holds the centrifugal weights controlling fuel delivery based on engine speed.
• Rotor Blades: Sliding vanes that pressurize fuel inside the pump’s rotor.
• Speed Wrench: A hand tool used to rotate the pump shaft manually during testing.
Manual Testing and Injector Spray Pattern
To further validate the rebuild, the operator connected the pump to a set of used injectors outside the machine. After bleeding the lines, a half-inch drill was used to spin the pump shaft. Once primed, the injectors began spraying with a consistent pattern. Though not a substitute for a calibrated injector tester, this method confirmed that the pump could build pressure and actuate the injectors.
This kind of bench testing is common among field mechanics who lack access to formal test stands. It’s a testament to the pump’s mechanical design that it can be tested with basic tools and still deliver reliable performance.
Timing and Installation Precautions
Before installing the pump, the operator ensured the engine was set to top dead center (TDC) on cylinder #1. The drive shaft and pump rotor were aligned using timing marks—critical for proper injection sequencing. Failure to align these dots can result in the pump firing 180 degrees out of phase, causing misfires or no-start conditions.
Advice from experienced rebuilders includes:
• Always tie the throttle lever back during assembly to prevent internal damage
• Confirm dot-to-dot alignment between the drive shaft and rotor
• Avoid flipping the first seal during shaft installation
Fuel Tank Contamination and System Cleanup
After installing the pump, the operator discovered that no fuel was flowing from the tank. Upon inspection, the sediment bowl was packed with rust and sludge, and the drain valve was seized. This level of contamination is common in older machines stored outdoors or run with untreated diesel.
To avoid damaging the freshly rebuilt pump, the operator bypassed the tank entirely, using a clean container of fuel with inlet and return lines. This method is often used during troubleshooting or startup after fuel system repairs.
Recommendations for tank cleanup:
• Remove and pressure wash the tank interior
• Replace the sediment bowl and drain valve
• Flush all lines with clean diesel before reconnecting to the pump
• Install a new inline filter rated for 10–15 microns
Initial Startup and Performance Observations
The dozer started and ran, with hydraulics functioning normally. However, it lacked movement, and shuttle fluid appeared to have dropped after running. Additionally, cylinder #1 was smoky and sluggish on startup, though it improved after bleeding and a small ether assist.
Possible causes include:
• Air trapped in the injector lines
• Weak spray pattern from used injectors
• Shuttle transmission fluid leak or internal bypass
To resolve these issues:
• Replace or test injectors using a calibrated pop tester
• Recheck shuttle fluid level and inspect for leaks around the throttle shaft
• Monitor exhaust color and engine response during warm-up
Conclusion
Rebuilding a Roosa Master pump without factory tools is a bold undertaking, but with careful research, attention to detail, and field ingenuity, it can be done successfully. The Case 350’s fuel system, while mechanically straightforward, demands precision in timing and cleanliness in fuel delivery. This story reflects the spirit of hands-on equipment ownership—where perseverance, resourcefulness, and a bit of grease can bring a machine back from the brink.
The Case 350 crawler dozer, equipped with the 188 cubic inch diesel engine, was a staple in compact earthmoving during the 1970s and 1980s. Its mechanical simplicity and rugged build made it popular among small contractors and landowners. The engine’s fuel delivery system relies on a Roosa Master rotary injection pump—a compact, cam-driven unit known for its reliability and precision metering. Over time, however, these pumps suffer from internal wear, fuel contamination, and seal degradation, leading to hard starts, poor injection timing, and eventual failure.
From Rusted Core to Functional Pump
One operator undertook the challenge of rebuilding a Roosa Master pump that had been sitting in poor condition. The pump was stripped down, cleaned, and fitted with:
• A new transfer pump liner
• Fresh rotor blades
• An updated governor weight retainer
• All new O-rings and seals
The rebuild was done manually, without specialized test benches. To verify functionality, the pump was mounted in a vise and rotated using a speed wrench. Remarkably, it began drawing fuel immediately, even with minimal cranking. This indicated that the transfer pump and rotor assembly were sealing properly and generating suction.
Terminology Clarification
• Transfer Pump Liner: A sleeve inside the pump housing that guides fuel into the rotor cavity.
• Governor Weight Retainer: A component that holds the centrifugal weights controlling fuel delivery based on engine speed.
• Rotor Blades: Sliding vanes that pressurize fuel inside the pump’s rotor.
• Speed Wrench: A hand tool used to rotate the pump shaft manually during testing.
Manual Testing and Injector Spray Pattern
To further validate the rebuild, the operator connected the pump to a set of used injectors outside the machine. After bleeding the lines, a half-inch drill was used to spin the pump shaft. Once primed, the injectors began spraying with a consistent pattern. Though not a substitute for a calibrated injector tester, this method confirmed that the pump could build pressure and actuate the injectors.
This kind of bench testing is common among field mechanics who lack access to formal test stands. It’s a testament to the pump’s mechanical design that it can be tested with basic tools and still deliver reliable performance.
Timing and Installation Precautions
Before installing the pump, the operator ensured the engine was set to top dead center (TDC) on cylinder #1. The drive shaft and pump rotor were aligned using timing marks—critical for proper injection sequencing. Failure to align these dots can result in the pump firing 180 degrees out of phase, causing misfires or no-start conditions.
Advice from experienced rebuilders includes:
• Always tie the throttle lever back during assembly to prevent internal damage
• Confirm dot-to-dot alignment between the drive shaft and rotor
• Avoid flipping the first seal during shaft installation
Fuel Tank Contamination and System Cleanup
After installing the pump, the operator discovered that no fuel was flowing from the tank. Upon inspection, the sediment bowl was packed with rust and sludge, and the drain valve was seized. This level of contamination is common in older machines stored outdoors or run with untreated diesel.
To avoid damaging the freshly rebuilt pump, the operator bypassed the tank entirely, using a clean container of fuel with inlet and return lines. This method is often used during troubleshooting or startup after fuel system repairs.
Recommendations for tank cleanup:
• Remove and pressure wash the tank interior
• Replace the sediment bowl and drain valve
• Flush all lines with clean diesel before reconnecting to the pump
• Install a new inline filter rated for 10–15 microns
Initial Startup and Performance Observations
The dozer started and ran, with hydraulics functioning normally. However, it lacked movement, and shuttle fluid appeared to have dropped after running. Additionally, cylinder #1 was smoky and sluggish on startup, though it improved after bleeding and a small ether assist.
Possible causes include:
• Air trapped in the injector lines
• Weak spray pattern from used injectors
• Shuttle transmission fluid leak or internal bypass
To resolve these issues:
• Replace or test injectors using a calibrated pop tester
• Recheck shuttle fluid level and inspect for leaks around the throttle shaft
• Monitor exhaust color and engine response during warm-up
Conclusion
Rebuilding a Roosa Master pump without factory tools is a bold undertaking, but with careful research, attention to detail, and field ingenuity, it can be done successfully. The Case 350’s fuel system, while mechanically straightforward, demands precision in timing and cleanliness in fuel delivery. This story reflects the spirit of hands-on equipment ownership—where perseverance, resourcefulness, and a bit of grease can bring a machine back from the brink.
