Irregularities in the shape of indicator diagrams are indications of faulty engine operations. If irregularity seems for all units, problem may be common like faults in fuel oil system, intake air, turbocharger, air cooler, exhaust, etc. When the irregularity is confined to a single unit, problem could be of fuel injectors, fuel pump, exhaust valve, etc.

Early Ignition

Indications and Effects

• Abnormally high peak pressure of the unit is recorded at the top of the piston stroke.
• Knocking sound comes out of the engine due to heavy loads passed to bearings via running gear.
• Early ignition causes increased thermal efficiency of the engine. Also exhaust temperature reduces since combustion starts long before it is supposed to. But the shock loads and vibrations results in damage of the engine.

Causes

• Incorrectly adjusted or accidentally changed fuel pump timing
• Damaged or incorrectly set fuel valve or fuel injector
• Undesired fuel quality
• Parts inside the cylinder are overheated.

Late Ignition

Indication and Effects

• A rise in expansions line is recorded in the later part of piston stroke
• Since burning of fuel continues, exhaust gas temperature and pressure increases, causing black smoke at engine exhaust.
• Unburnt carbon deposits fouls exhaust system, cause damage to exhaust valve and seat, turbocharger surges and there are chances of uptake fires in exhaust gas economizer.
• Elevated temperatures inside cylinders cause breaking up of lubrication and increased wear of liners, piston rings, burning of piston crown, etc.

Causes

• Slow fuel combustion
• Quality of fuel is less
• Low temperature of fuel (Means high viscosity)

Leaky Fuel Injector

Partly Choked Fuel Valve

Low Compression

Exhaust Valve Opening

Choked Exhaust

Indications and Effects

• Power loss in the unit
• Increased exhaust temperature
• Turbocharger surging
• adversely affect scavenging efficiency

Causes

• Improper combustion
• Increased cylinder lube oil