Engines
Why won't my marine diesel start after winter lay-up?
After lay-up the usual causes are a flat or tired battery, air in the fuel system, a clogged filter or stale, contaminated diesel. Check batteries and fuel first. If the engine turns over briskly but never fires, the problem is almost always fuel or air rather than the starter.
Start with the simple observation: does it crank? A slow, laboured crank or a click points at batteries, terminals or the starter. A healthy crank with no fire points at fuel delivery — air in the lines after filter changes, a blocked primary filter, or diesel that has grown a bug over the winter.
Diesel bug is the seasonal favourite. Water in the bottom of the tank lets microbial growth form a dark sludge that blocks filters within minutes of running. If your pre-filter bowl looks murky or the filter is black, treat it as a fuel problem and get the tank checked rather than repeatedly changing filters.
Never keep cranking. Repeated long cranks flatten the battery, can fill the exhaust with water on a raw-water-cooled engine and risk hydraulic lock. Thirty seconds at a time, with a rest, is the limit.
Related questions
- Is it safe to keep trying the starter?
- No. Repeated cranking on a raw-water-cooled engine can flood the exhaust and back water into a cylinder. Crank in short bursts and stop if it hasn't fired after a few attempts.
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