08-08-2025, 10:33 PM
Overview: Entrenched Starter Troubles in Idle Ex‑Komatsu Excavators
A Komatsu PC150LC excavator, powered by a four‑cylinder Cummins engine, sat unused for several weeks. When the operator returned, it simply “would not start.” The engine would respond briefly to starter fluid—suggesting fuel was reaching the cylinders—but after changing all filters and the fuel‑shutdown solenoid, it still only “sounded like it wanted to fire.” This kind of idle‑induced ignition failure is surprisingly common when diesel engines sit unused—especially in damp environments.
Underlying Causes and Expert Insights
Equipment experts often point to cylinder ring sticking through rust or condensation: when a diesel engine sits idle in humid settings, moisture accumulates in the cylinders, causing piston rings to partially seize. The engine cranks, but compression may be severely reduced, preventing sustained combustion. A practical quick‑fix is to spray lubricant (such as penetrating oil) into the intake manifold and idle the engine—this can help free the rings and restore compression.
A user from Venezuela shared such wisdom:
Real‑World Analogy: The Seaside Boat's Rusty Engine
Consider a fishing boat left in the harbor all winter. When spring arrives, the crank turns, but the engine just grinds without catching. A mechanic sprays penetrating oil into the intake. After a few tries at gentle cranking, the engine coughs, then roars back to life—its rings freed from rust’s grip. Similarly, the PC150LC may be “waking up” with a boost of intake lubricant.
Expanded Diagnostic & Fix Strategy
Here’s a systematic troubleshooting path for “no‑start” in similarly idle diesel excavators:
A construction crew parked an excavator overnight during light rain. The next morning, it cranked but refused to fire. A technician suspected moisture had seeped into the cylinders. They sprayed penetrating oil into the air intake, cranked gently, and the engine caught after several attempts. After running for fifteen minutes, it started reliably—drying the cylinder walls.
Glossary of Key Terms
When a diesel excavator like the Komatsu PC150LC resists starting after sitting idle, especially in humid conditions, stuck piston rings often lie at fault. Swapping filters and fuel components is good practice—but when the engine “seems eager but can’t fire,” introducing penetrating oil into the intake and gentle cranking can restore compression. With patience and this technique, an engine that “sounds like it wants to fire” may well roar back to life.
Let me know if you'd like expanded diagnostics, detailed maintenance schedules, or comparisons with other excavator models.
A Komatsu PC150LC excavator, powered by a four‑cylinder Cummins engine, sat unused for several weeks. When the operator returned, it simply “would not start.” The engine would respond briefly to starter fluid—suggesting fuel was reaching the cylinders—but after changing all filters and the fuel‑shutdown solenoid, it still only “sounded like it wanted to fire.” This kind of idle‑induced ignition failure is surprisingly common when diesel engines sit unused—especially in damp environments.
Underlying Causes and Expert Insights
Equipment experts often point to cylinder ring sticking through rust or condensation: when a diesel engine sits idle in humid settings, moisture accumulates in the cylinders, causing piston rings to partially seize. The engine cranks, but compression may be severely reduced, preventing sustained combustion. A practical quick‑fix is to spray lubricant (such as penetrating oil) into the intake manifold and idle the engine—this can help free the rings and restore compression.
A user from Venezuela shared such wisdom:
Quote:“the pistons rings goes to glued by the humidity... try to start the engine with a spray lubricant put in the admission and start the engine at idle velocity.”This advice effectively diagnosed poor compression from ring adhesion.
Real‑World Analogy: The Seaside Boat's Rusty Engine
Consider a fishing boat left in the harbor all winter. When spring arrives, the crank turns, but the engine just grinds without catching. A mechanic sprays penetrating oil into the intake. After a few tries at gentle cranking, the engine coughs, then roars back to life—its rings freed from rust’s grip. Similarly, the PC150LC may be “waking up” with a boost of intake lubricant.
Expanded Diagnostic & Fix Strategy
Here’s a systematic troubleshooting path for “no‑start” in similarly idle diesel excavators:
- Air system check
- Remove or inspect the air filter. A heavily clogged or dirty intake can starve the engine of air when cranking.
- Remove or inspect the air filter. A heavily clogged or dirty intake can starve the engine of air when cranking.
- Monitor dashboard indicators
- Watch for alternator or warning lights on the monitor panel when turning the key. A flashing alternator light may signal electrical faults or low battery voltage.
- Watch for alternator or warning lights on the monitor panel when turning the key. A flashing alternator light may signal electrical faults or low battery voltage.
- Fuel delivery components
- Replace filters (fuel, water‑separators) and the fuel‑shutdown solenoid to rule out interruptions in fuel supply or premature fuel cutoff.
- Replace filters (fuel, water‑separators) and the fuel‑shutdown solenoid to rule out interruptions in fuel supply or premature fuel cutoff.
- Compression testing / freeing stuck rings
- Spray penetrating lubricant into the intake and crank at low RPM to restore compression. If that fails, a proper compression gauge test may confirm low cylinder pressure.
- Spray penetrating lubricant into the intake and crank at low RPM to restore compression. If that fails, a proper compression gauge test may confirm low cylinder pressure.
- Confirmed starting
- Once the engine fires with intake spray and holds idle, let it run—this can dry out cylinders and keep rings free.
- Once the engine fires with intake spray and holds idle, let it run—this can dry out cylinders and keep rings free.
A construction crew parked an excavator overnight during light rain. The next morning, it cranked but refused to fire. A technician suspected moisture had seeped into the cylinders. They sprayed penetrating oil into the air intake, cranked gently, and the engine caught after several attempts. After running for fifteen minutes, it started reliably—drying the cylinder walls.
Glossary of Key Terms
- Starter fluid: A volatile aerosol used to prime an engine for ignition when normal starting fails.
- Fuel‑shutdown solenoid: A valve that cuts off fuel flow when the engine is stopped; if faulty, it may prevent fuel delivery even if filters are clear.
- Penetrating lubricant: Low‑viscosity oil that seeps into tight spaces, useful for loosening rust‑stuck piston rings.
- Compression: The pressure achieved in a cylinder during the compression stroke, essential for diesel ignition.
- Idle cranking: Gently running the engine at low RPM to reduce mechanical stress during difficult starts.
When a diesel excavator like the Komatsu PC150LC resists starting after sitting idle, especially in humid conditions, stuck piston rings often lie at fault. Swapping filters and fuel components is good practice—but when the engine “seems eager but can’t fire,” introducing penetrating oil into the intake and gentle cranking can restore compression. With patience and this technique, an engine that “sounds like it wants to fire” may well roar back to life.
Let me know if you'd like expanded diagnostics, detailed maintenance schedules, or comparisons with other excavator models.
