Overview
If an alternator is the soul of the generator, then the diesel engine is the heart that keeps the generator going. Regular monitoring and maintenance will prevent dire situations, such as machine failure and operational downtime. When the diesel engine begins to lose power or efficiency, several factors contribute to its decline. It is crucial to address these issues before they worsen and lead to complete engine failure.
In certain circumstances, engine overhauling is the most effective way to address a problematic diesel engine, as it can resolve issues with the engine and save you a significant amount of money compared to replacing it. It would be beneficial to understand and recognise the signs. As a rule of thumb, an overhaul is vital when the diesel engine exhibits any of the following symptoms:
Increased Blow-by Gas
Blow-by gas occurs when combustion gases leak between a piston and the cylinder wall into the crankcase. Measure the flow rate of the blow-by gas and make a judgment. For the measuring method and judgement criteria, do refer to the engine manufacturer’s maintenance instructions.
CAUSE OF INCREASED BLOW-BY GAS
- Worn piston rings and/or cylinder liners
- Worn valve stems and/or valve guides
- Clogged breather
- Abnormal combustion
- Clogged PCV (Oil separator)
- Clogged air cleaner
Increased Engine Oil Consumption
The engine oil consumption may vary depending on the usage environment, oil type or operating conditions. For the generator, the oil consumption should be checked against its ratio to fuel consumption.
| Cause of Increased Oil Consumption | Observable Sign |
|---|---|
| Oil leakage due to a faulty oil seal, gasket, or other component | Oil leakage visible on the exterior of the engine |
| Damaged oil cooler | Oil mixed with cooling water |
| Worn or broken oil ring | Reduced compression pressure |
| Worn cylinder liner(s) | Increased blow-by gas |
| Worn valve guides and/or valve stems | — |
Reduced Compression Pressure
A diesel engine with low compression pressure may experience poor startability. Therefore, it is advisable to identify the root cause by measuring the engine’s compression pressure.
How to measure compression pressure:
- Remove the nozzle holder and install a compression pressure gauge using the appropriate adaptor.
- Crank the engine using the starter motor and run it at the specified idle speed to confirm that the measured compression pressure falls within the specified range.
| Cause of Reduced Compression Pressure | Observable Sign |
|---|---|
| Worn piston rings and/or cylinder liners | Excessive engine oil consumption |
| Improper contact between the valve and valve seat | Abnormal exhaust smoke colour |
| Poor startability | — |
| Premature degradation of engine oil | — |
Insufficient Engine Output
Several factors may contribute to the abnormal loss of output from the diesel engine. Probable causes include the following:
| Cause of Insufficient Engine Output | Observable Sign |
|---|---|
| Oil leakage due to a faulty oil seal, gasket, or other component | Oil leakage visible on the exterior of the engine |
| Damaged oil cooler | Oil mixed with cooling water |
| Worn or broken oil ring | Reduced compression pressure |
| Worn cylinder liner(s) | Increased blow-by gas |
| Worn valve guides and/or valve stems | — |
| Fuel pump failure | Black smoke emitted from the engine |
| Clogged injection nozzles | — |
| Improperly timed fuel injection | — |
| Turbocharger seizure | — |
Conclusion
In this article, we have identified the different fault diagnosis methods for a diesel engine and the probable causes of the symptoms. If you have any further questions regarding machine servicing, please don’t hesitate to contact us for assistance.
