Fuel and Oil Pressure Failures in the 2008 John Deere 325 Skid Steer

[MikePhua]

Overview of the John Deere 325 Skid Steer
The John Deere 325 skid steer loader was introduced in the mid-2000s as part of Deere’s compact equipment lineup. Designed for versatility in construction, landscaping, and agricultural tasks, the 325 featured a turbocharged diesel engine producing around 70 horsepower, hydrostatic drive, and a rated operating capacity of approximately 2,500 lbs. With over 10,000 units sold globally, the 325 became a popular choice for contractors seeking a balance of power and maneuverability.
Its engine, typically a 4024T or similar four-cylinder diesel, relies on a mechanical fuel lift pump driven off the camshaft, and an internal oil pump housed within the timing gear cover. These systems are critical to engine startup, lubrication, and long-term reliability.
Fuel Pump Drive and Camshaft Gear Issues
The mechanical fuel pump on the John Deere 325 is actuated by a lobe on the camshaft. If the camshaft gear bolt loosens or shears, the gear may slip, causing the camshaft to rotate out of sync or stop turning altogether. This results in a loss of fuel delivery, as the pump no longer receives mechanical input.
Symptoms include:

• No fuel flow during cranking
  
• Engine cranks but does not fire
  
• Fuel hoses remain dry despite good tank supply
  
• Shutoff solenoid receives voltage but pump remains inactive
  

In one case, the operator suspected a camshaft gear failure and planned to remove the front cover to inspect gear alignment. This type of failure is rare but catastrophic, often requiring full engine disassembly.
Fuel Check Valve and Pump Failure
Before assuming internal failure, it’s essential to inspect the fuel system for simpler faults. The check valve, located at the barbed fitting on the engine block, can become clogged with debris, preventing fuel from reaching the pump. Additionally, the pump itself may suffer from seized plungers or internal contamination.
Recommended steps:

• Verify clean fuel supply from tank
  
• Inspect and clean check valve at fuel inlet
  
• Replace fuel lift pump if no output during cranking
  
• Prime system manually after pump replacement
  

In the documented case, replacing the pump and priming the system restored fuel flow, and the engine briefly started before shutting down due to a new issue—zero oil pressure.
Zero Oil Pressure and Internal Damage
After resolving the fuel issue, the operator encountered a low oil pressure warning. Mechanical gauge readings confirmed zero pressure at the sender port near the oil filter housing. Further inspection revealed:

• No oil flow to turbocharger supply line
  
• Oil filter remained dry
  
• Metallic particles present in drained oil
  

These signs point to a failed oil pump or blocked pickup tube. On Deere 4024 engines, the oil pump and pressure regulator are located within the timing gear cover, and the pickup tube is bolted to both the cover and the engine block. Accessing these components requires engine removal and oil pan disassembly.
Potential causes include:

• Oil pump gear failure or shaft shearing
  
• Pressure regulator valve stuck open
  
• Pickup tube blockage due to sealant contamination or foreign debris
  

A technician shared an example of a 4024 engine with a pickup tube clogged by Hylomar sealant—a non-hardening compound used during factory assembly. Such blockages can starve the pump and lead to rapid engine damage.
Rebuild Considerations and Cost Management
With no oil pressure and signs of internal wear, the engine must be removed and inspected. Rebuild options include:

• Full overhaul kits priced between $1,000–$1,500 USD
  
• Replacement oil pump and regulator components
  
• Crankshaft and cylinder wall inspection for scoring or galling
  
• New bearings, seals, and gaskets
  

Remanufactured engines are available but often exceed $9,000 USD, making rebuilds more economical for owner-operators. Sourcing parts from reputable suppliers and verifying compatibility with engine serial numbers is essential.
Anecdote from New Jersey
An equipment mechanic in New Jersey acquired a 2008 JD 325 with 1,500 hours and no service history. After diagnosing fuel pump failure and replacing it, he discovered the oil pressure issue. Upon teardown, he found the pickup tube partially blocked by sealant and the oil pump gear worn. He rebuilt the engine over two weeks and now uses the machine for grading and snow removal. He recommends checking oil pressure manually before first startup on any used machine.
Preventive Measures for Long-Term Reliability
To avoid similar failures:

• Change engine oil and filter every 250 hours
  
• Use high-quality diesel and fuel additives to prevent pump contamination
  
• Inspect oil pressure with a mechanical gauge during startup
  
• Avoid excessive sealant during engine assembly
  
• Monitor for early signs of fuel starvation or oil pressure drop
  

Operators should maintain detailed service logs and perform visual inspections of fuel and oil systems monthly. Early detection of pressure anomalies can prevent catastrophic engine damage.
Conclusion
The 2008 John Deere 325 skid steer is a capable machine, but its mechanical fuel and oil systems require vigilance. Failures in the camshaft-driven fuel pump or oil pump assembly can lead to no-start conditions and internal engine damage. With proper diagnostics, part sourcing, and preventive care, these issues can be resolved and avoided. For those restoring or maintaining older Deere equipment, understanding the interplay between camshaft, fuel delivery, and oil pressure is essential to keeping the machine running strong.