Injector Setup and Engine Identification on the Versatile 875 Tractor

[MikePhua]

Versatile 875 Background and Engine Evolution
The Versatile 875 is a four-wheel-drive agricultural tractor produced in the late 1970s and early 1980s by Versatile Manufacturing, a Canadian company known for pioneering articulated tractors. The 875 was part of the company’s 800 Series, which gained popularity for its simplicity, durability, and power. With an operating weight of over 30,000 lbs and a drawbar horsepower rating around 280 hp, the 875 was designed for heavy tillage and broad-acre farming.
Most Versatile 875 units were powered by the Cummins NT855-A280, a turbocharged inline-six diesel engine. This engine belongs to the NT855 family, which was widely used in construction, mining, and agricultural equipment throughout the 1970s and 1980s. Over time, Cummins introduced multiple variants of the 855, including the Big Cam series, which featured improved fuel efficiency and electronic timing.
Identifying the Correct Injector Setup
When servicing or rebuilding the NT855 engine, proper injector setup is critical. The injector adjustment sequence typically involves:

• Setting injector plunger height
  
• Adjusting crosshead clearance
  
• Setting valve lash
  

However, the NT855 family includes both small cam and big cam variants, each with different injector types and adjustment procedures. The small cam engines use mechanical timing, while big cam engines incorporate pressure-time (PT) fuel systems with variable timing based on oil pressure.
To determine the correct procedure, technicians must first identify the engine variant. This requires locating the engine serial number, usually stamped on a data plate near the fuel pump or on the block itself. Without this number, it’s difficult to confirm whether the engine uses small cam or big cam injectors.
Challenges in Cold Weather and Remote Locations
In one case, the tractor was parked 500 miles away during winter, making it difficult to retrieve the engine serial number. This highlights a common issue in agricultural service work—equipment is often stored in remote areas, and harsh weather can delay diagnostics. Technicians working in northern climates recommend keeping a log of serial numbers and service history in a centralized database or physical binder for quick reference.
Injector Types and Setup Differences
The NT855 engine may use one of the following injector types:

• Top-stop injectors: Require adjustment with the injector plunger fully depressed
  
• Non-top-stop injectors: Adjusted based on crosshead clearance and valve lash sequence
  

Incorrect setup can lead to poor combustion, excessive smoke, and reduced power. In the case of the Versatile 875, the dealer noted that the engine smoked continuously after the pump was “recently set up,” suggesting possible injector misadjustment or timing error.
Recommendations for Accurate Setup

• Retrieve the engine serial number before attempting injector setup
  
• Consult Cummins service literature specific to the NT855 variant
  
• Use a dial indicator to measure injector plunger travel if top-stop injectors are suspected
  
• Adjust crossheads and valves in the correct firing order, typically 1-5-3-6-2-4 for inline-six engines
  
• Verify fuel pump timing and ensure the PT system is calibrated if applicable
  

Conclusion
Servicing the Versatile 875’s NT855 engine requires careful identification of the injector type and adjustment sequence. With multiple variants in circulation, the engine serial number is the key to unlocking accurate service data. Whether working in a heated shop or a frozen field, technicians must combine mechanical precision with historical awareness to keep these legacy tractors running strong. The NT855 remains a testament to Cummins’ engineering legacy, and the Versatile 875 continues to earn its place in the fields of North America.