A few weeks back, one of our engineers was carrying out a maintenance visit to a Cummins KTA38.
On paper, the maintenance looked relatively routine, but when on site a persistent problem was raised.
The engine was reported to be suffering from erratic engine speed during start up and off load operation, making synchronisation difficult. While thesymptom was straightforward, the underlying cause needed to be correctly identified and resolved from a list of possibilities.
Starting with the fundamentals
Following delays caused by weather and isolation constraints, our engineer began with the scheduled maintenance activities including the changeout of fuel, oil and coolant filters before setting the valve clearances and completing injector setting checks.
With these fundamentals carried out, the engine was run up again but still hunting. This discounted three possibilities:
· Filters restricting flow through blockages.
· Incorrect valve clearances
· Injectors incorrectly set
These valve clearance and injector settings are critical on engines of this type, as incorrect clearances or injector preload can directly influence combustion balance and governor response.
Given the symptoms, attention turned to the fuel delivery system. A replacement PT fuel pump was supplied and installed to try and stabilise fuel delivery and eliminate the hunting.
However, test running showed that with the new pump fitted, the engine would not accelerate beyond 620 RPM, so instead of resolving the hunting it introduced a new problem!
The new challenge of reduced engine speed
With the drop in engine speed, the focus shifted to try and get the RPMs back up, alongside resolving the hunting. As the only thing that was changed was the fuel pump, the old one was refitted.
This was despite the new pump being new, genuine and matching the same part number as the original. Refitting the old pump resolved the engine speed issue, but the original hunting issue remained.
The next focus was on the electronic governor, which was replaced alongside checks with the magnetic pick up and actuator. Each change was followed by test running and showed an improvement in resolving the hunting.
Whilst governors are preset, they can often need calibrating to match the installation, especially if it has been in place for a length of time and is likely to have been tweaked to match operational needs.
Before setting the governor, another secondary issue was identified. The actuator was not sealing correctly, so this needed to be addressed to ensure fuel pressure was not being affected.
Once the governor settings were changed and actuator fitting resealed, the generator was able to finally run steady and synchronise with the busbars and complete a load test before being returned to standby service.
If you’re faced with engine hunting, check these three things.
Whilst fuel hunting can be caused by a single failure, there are many possible causes, so a structured approach is best to get it resolved.
If you find yourself faced with a similar problem, we’d recommend:
· Check the fundamentals, like possible blockages, injector and valve settings
· Look at fuel delivery system – fuel pumps and injectors
· Check fuel control system – usually a separate governor, sensors and actuators
Just as importantly, the visit reinforced the value of structured fault finding. Each change was tested, each result observed, and conclusions were drawn only when evidence supported them.
Final thoughts – looking for the cause behind the symptoms
Engines that hunt are telling you something. Resolving the issue is not about quick fixes but about understanding how mechanical, fuel, and control systems interact.
At Bartech Marine, our approach is always to work methodically, verify assumptions, and leave engines not just running, but running correctly.
This is how intermittent problems are turned into reliable outcomes, and why process matters as much as parts.
Also, just because you’re fitting a new part, like we did with the fuel pump, doesn’t mean that it is going to be correct. Always carry out your own checks!
