What is the difference between a primary and secondary fuel filter on a marine diesel?

A. Primary (Racor/CAV type): large housing with a water separator bowl and coarse filter — removes water and large particles, inspected regularly. Secondary (fine filter): smaller, close to the injection pump, removes very fine particles — protects the high-pressure injection system from abrasive damage

B. Only the secondary filter needs regular replacement — the primary is self-cleaning

C. The primary filter is inside the fuel tank; the secondary is between tank and engine

D. Primary and secondary filters are identical — either can be replaced independently

A. Diesel engines work at lower compression ratios than petrol engines for safety

B. Compression ignition: diesel fuel is ignited by the heat of highly compressed air (compression ratio ~22:1) — no spark plugs are used. Fuel is injected into the compressed air at the moment of ignition

C. Diesel engines use spark plugs but fire in a different sequence to petrol engines

D. Diesel engines use carburettors to mix fuel and air before compression

A. Compression, ignition, induction, exhaust — the compression happens before air enters

B. Ignition, compression, induction, exhaust

C. Induction (air in): piston down, air drawn into cylinder. Compression: piston up, air compressed to high temperature. Power (ignition): fuel injected, combustion drives piston down. Exhaust: piston up, exhaust gases expelled

D. Induction, power, compression, exhaust