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What this video covers

Nigel Calder corrects a common misconception: poor compression in a diesel engine does not cause black exhaust smoke.▶ 0:53 Black smoke signals a fuel injection problem — improper fuel delivery or poor atomization — not a compression failure.▶ 1:43 A diesel fires by compressing air until it reaches ignition temperature, then injecting fuel; if compression is adequate, the engine either ignites cleanly or not at all.▶ 0:38 The primary sign of inadequate compression is the engine failing to start.▶ 0:00 How much compression loss triggers that failure depends on ambient air temperature: cold air demands higher compression to reach ignition temperature, so a marginal engine that starts in warm climates may refuse to fire in cold conditions.▶ 1:01 Preheaters offset this relationship.▶ 1:07 Calder emphasizes that compression and temperature interact continuously as an engine wears, and that no single compression threshold guarantees ignition independent of ambient conditions.▶ 0:53

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