Why Main Engine may fail to start?

asked 20 Apr '17, 08:18

April 20, 2017, 8:18 a.m.
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Actual causes of failed start depend on engine design and operational condition. Remember that regular maintenance/overhaul routines should be followed and it will ensure trouble less starting. Below is a list of most common problems and ways to solve them:

1.Starting system failure

1.1 Starting air system:

1.1.1 Insufficient air pressure. Most makers require at least 20 Bars for assured start. Check line for leaks both main and control.
1.1.2 Control air line failure including pilot, control, shut-off valves malfunctioning due to moisture, dirt, worn seals and O-ring. Failure to drain water from starting air bottles could lead to formation of oil-water mixtures. This mixture could interrupt normal operation of control air system components. Inspect, clean replace worn O-rings and seals.    
1.1.3 Main starting valve / shut off valve could seize and stuck  Worn seals will lead to failure as well. Regular maintenance/overhaul required.
1.1.4 Starting air distributor may fail if worn enough. Overhaul and replace worn parts   
1.1.5 Starting air motor (if fitted ) may fail due to internal wear.

1.2 Electrical starting system:

1.2.1 Batteries charge low. Check batteries and charger, recharge or replace. 
1.2.2 Starter el. motor or its circuit failure

2.Fuel system failure

2.1 Not enough fuel pressure due to clogged filters or pump failure. Check and clean filters, check fuel pump.
2.2 Water in oil. Regular draining and constant purifying should never be forgotten. Accumulation of water in fuel system requires flushing of entire fuel system and could lead to fuel injectors and fuel injection pumps damage.
2.3 Too high  fuel viscosity. This may happen when engine operates on HFO but its fuel injection pumps and valves not designed for permanent fuel circulation for heating purposes. If such engine stoped without previously being changed over to DO it may not start later.  Always follow correct fuel changeover procedure. Restart engine asap if sudden stop happened while operating on HFO.
2.4 Misfire due to worn fuel injection pumps and valves. Replace and overhaul worn components. Such issue never happen at once. Continuos combustion monitoring required to evaluate fuel injection components condition.

3. Cylinder unit failure. If piston ring, piston or liner badly worn insufficient compression pressure created and ignition became impossible. In this case engine could not reach starting RPM for ensured ignition. Common faults are below

3.1 Broken and seized piston rings. Could be identified either by visual inspection (2 stroke engines with scavenging ports) or measuring cylinder compression pressure. In case some piston rings fail piston must be overhauled asap.
3.2 Liner wear must be measure during piston overhaul. Liners which worn over the stated limit must be replaced. 
3.3 Failed exhaust and inlet valves (if installed). Valves may have blow-by or stuck in valve guide. Could be identified by drop in compression pressure and exhaust temperature rise.

4. Various starting interlocks dedicated prevent starting in non-start condition. Engaged turning gear, engaged clutch (in case of reduction gear connected), engine not prelubricated, low LO pressure, wrong camshaft position etc will not let engine to start. Often the problem is only in failed sensor. Identify activated interlock/sensor and troubleshoot.

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answered 21 Apr '17, 08:50

April 21, 2017, 8:50 a.m.
SeamenExchangeExpert's gravatar image

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edited 07 Jun '17, 23:51

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