The alternator and raw water pump on many engines are driven by a V-belt. How do you check belt condition and tension?

A. Condition: look for cracks, fraying, glazing, or missing chunks — replace if any present. Tension: press midway between pulleys — correct tension gives approximately 10-15mm deflection under moderate thumb pressure (check engine manual for exact specification). A loose belt slips and squeals; too tight damages alternator bearings

B. Tighten the belt until it has zero deflection — this prevents slipping under high load

C. Replace V-belts only when they break — visual inspection gives no useful information

D. V-belts never require adjustment — they are self-tensioning

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