Reviving the Vibromax AT60 with Hatz Diesel After Sudden Failure

[MikePhua]

History of Vibromax and the AT60 Series
Vibromax, originally a German manufacturer of compaction equipment, gained recognition in the 1970s and 1980s for producing durable walk-behind and ride-on compactors. The AT60 was one of its mid-range tamping compactors, designed for trench work, road patching, and foundation preparation. With a working weight around 600 kg and a centrifugal force exceeding 13 kN, the AT60 was widely used in municipal and contractor fleets across Europe and Australia.
The AT60 was often paired with Hatz diesel engines, particularly the single-cylinder air-cooled models like the E673 or 1B20. These engines were known for their simplicity, mechanical reliability, and ability to run in dusty, hot environments without liquid cooling systems.
Terminology Annotation

• Crank Handle Start: A manual engine start method using a hand crank to rotate the flywheel. Common in older diesel engines before electric starters became standard.
  
• Injector Squeak: A high-pitched sound heard during manual cranking, indicating fuel is being pressurized and released through the injector nozzle.
  
• Choke Lever: Though not a true choke in diesel engines, this mechanical lever often adjusts fuel delivery or timing advance during cold starts.
  

Symptoms Leading to Engine Failure
The compactor initially showed erratic behavior—engine speed fluctuating without operator input, followed by difficulty starting unless the choke lever was engaged. Eventually, it failed to start altogether. These symptoms suggest a progressive fuel delivery issue, likely originating from the injector pump or nozzle.
Possible causes include:

• Internal wear in the injector pump leading to inconsistent fuel metering
  
• Clogged injector nozzle disrupting spray pattern
  
• Air ingress into the fuel system from cracked lines or loose fittings
  
• Timing drift due to worn camshaft or linkage components
  

The fact that compression was still present and the injector squeak audible during cranking indicates that mechanical integrity may still be intact, narrowing the issue to fuel delivery.
Recommended Diagnostic Steps
To isolate the fault, a structured approach is essential:

• Remove and inspect the injector nozzle for carbon buildup or deformation
  
• Perform a compression test using a diesel-rated gauge to confirm cylinder health
  
• Check fuel lines for leaks, cracks, or air bubbles during priming
  
• Test the injector pump using a fuel spilling method to verify timing and pressure
  
• Inspect the mechanical choke lever to determine its function—whether it adjusts rack position, fuel quantity, or timing advance
  

If the injector spray pattern is weak or uneven, replacement or professional cleaning is advised. A healthy injector should produce a fine mist with a distinct crackling sound under pressure.
Repair Cost and Feasibility
Repairing a Hatz diesel injector pump can range from $150 to $600 depending on the model and availability of parts. Rebuilt injectors typically cost $80–$150, while new units may exceed $300. Labor costs vary by region, but in Australia or the U.S., expect $400–$800 for full pump service.
Given the age of the AT60, the decision to repair hinges on the machine’s structural condition and usage frequency. If the compactor frame, exciter, and drum are intact, a fuel system overhaul is economically viable. These machines often outlast their engines, and many operators have successfully repowered them with newer Hatz or Yanmar units.
Field Anecdotes and Practical Advice
In Queensland, a contractor revived a similar Vibromax unit by replacing the injector and flushing the fuel tank, which had accumulated algae due to long-term diesel storage. After cleaning the lines and installing a new filter, the engine started on the first crank.
In Wisconsin, a retired mechanic shared that older Hatz engines often suffer from timing drift due to camshaft wear. He recommended marking the original pump position before removal and using a dial indicator to reset timing during reinstallation.
Preventive Measures for Legacy Diesel Compactors

• Use biocide additives in diesel fuel to prevent microbial growth
  
• Replace fuel filters every 100 hours or annually, whichever comes first
  
• Store machines with full tanks to reduce condensation and rust
  
• Exercise the engine monthly to keep seals lubricated and prevent varnish buildup
  
• Label mechanical levers clearly to avoid misuse by inexperienced operators
  

Industry Trends and Legacy Equipment Support
While Vibromax was eventually acquired by BOMAG, many of its older models remain in service. Hatz continues to support legacy engines through its global dealer network, offering parts and technical documentation for models dating back to the 1970s.
In recent years, compactors have shifted toward electric start and Tier 4-compliant engines, but the simplicity of crank-start diesel units still appeals to operators in remote or rugged environments. Restoration communities have emerged online, sharing rebuild guides and sourcing rare parts for machines like the AT60.
Conclusion
The Vibromax AT60 with a Hatz diesel engine may be old, but its mechanical design offers a path to revival. With signs pointing to a fuel delivery fault, targeted diagnostics and modest investment can bring the machine back to life. For those who value durability over digital complexity, restoring such equipment is not just practical—it’s a tribute to engineering that endures.