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What to check if the engine will not turn on starting air?

Confirm there is enough air in the starting-air receiver and start the compressors if pressure is low; make sure the receiver and distributor valves are open and that control-air pressure is normal (about 7 bar). Check that the main starting (ball) valve is in the working position and that the turning-gear interlock is disengaged. Verify the control selectors are set correctly and, on a controllable-pitch plant, that the propeller is at zero pitch. If it still will not turn, suspect the starting-air distributor timing or leaking starting valves in the cylinder covers — pressure-test and overhaul as needed.

The engine turns on air but stops as soon as it is given fuel — what should be done?

This usually points to the manoeuvring/fuel linkage or the governor. Lubricate the manoeuvring gear and confirm the fuel pumps, rod connections and bearings move freely and that the fuel-pump index matches the test-bed setting. Check that the governor receives correct oil/booster pressure during the air-running period and that its pre-speed setting is high enough and held long enough. If the engine runs too long on air before fuel, shorten the starting-air period or adjust the start-level rpm.

Why does the engine run unevenly and fail to pick up speed after changing over to fuel?

Start the auxiliary blowers if they are not running, and check the scavenge-air limiter setting against the scavenge and exhaust pressures recorded at the same load on trials. Clean a blocked fuel filter and raise fuel pressure if it is low. A cylinder that is not firing — from a stuck suction or puncture valve, a disconnected index linkage, or a defective fuel valve — will also cause this; locate and correct the dead cylinder.

Exhaust temperature on one cylinder is high — what does it indicate?

The most common causes are a defective fuel valve or nozzle, or a leaking exhaust valve; a leaking exhaust valve typically shows as a temperature rise together with a drop in compression and maximum pressure and should be changed or overhauled. Blow-by past the piston rings gives a similar picture and may be heard as a hiss at the scavenge-box drain; if reducing index and increasing cylinder oil does not clear it, lift the fuel-pump roller guide or renew the rings. Also check that the fuel cam has not slipped.

All exhaust temperatures are rising together — where to look?

Treat it as an air-supply or combustion problem: check the scavenge-air (charge-air) cooler performance and clean fouled air and gas passages — turbine, blowers and air coolers — and check the exhaust back-pressure after the turbocharger. Confirm the fuel quality and treatment, and verify camshaft timing (maximum pressure and chain tension) in case the cam drive has shifted.

The engine speed keeps dropping — what are the likely causes?

Raise the fuel supply and circulating pump pressures if they are low and vent any air, gas or steam from the fuel system. Renew defective fuel valves or pumps, drain water from the fuel, and check whether the governor is limiting the index because of an abnormal load (fouled hull, shallow water, or a torque/scavenge limit). A scavenge-box fire or an activated slow-down can also pull the revs down — check pressures, temperatures and the protective devices.

What causes a smoky exhaust and what should be done?

Some smoke while accelerating is normal as the turbocharger catches up; heavy smoke during acceleration points to a wrong governor-limiter setting. Otherwise the cause is usually insufficient air — clean the turbine, blowers and air coolers and check engine-room ventilation — or defective fuel valves and nozzles. Persistent heavy smoke with falling revs can signal a fire in the scavenge-air box.

How should a scavenge-air box fire be handled?

Warning signs are a rising exhaust temperature on the affected unit, possible turbocharger surging, smoke from the air-inlet filter and a noticeably hot scavenge box. Reduce to slow and request permission to stop; on stopping, switch off the auxiliary blowers and shut off the fuel and lube-oil supply, then operate the scavenge-box fire-extinguishing system. Do not open the scavenge box or crankcase until the area has cooled below about 100 °C, then clean out all boxes and inspect the piston rods and liners. Keeping the auxiliary-blower switch in AUTO helps prevent unburnt fuel from accumulating.

What should be done at the first sign of oil mist or a possible crankcase explosion?

Treat an oil-mist-detector alarm seriously and keep clear of crankcase doors and relief valves. Reduce to the slow-down level, ask the bridge for permission to stop, and on stopping shut off the fuel supply and the auxiliary blowers; open the skylights, leave the engine room and keep away with fire-fighting equipment ready. Do not open the crankcase for at least 30 minutes; then, with the oil pump stopped and the turning gear engaged, locate the hot spot, look for squeezed-out bearing metal or discolouration, and repair it permanently before restarting. After any crankcase explosion, renew the relief-valve flame arresters.

The turbocharger is surging — what does it mean and how is it corrected?

An occasional surge during a crash stop or sharp manoeuvre is usually harmless if the turbocharger bearings are sound, but continuous surging must be stopped to avoid damaging the rotor. Work through the likely areas: the fuel system (low supply pressure, air or water in the fuel, a sticking pump or valve, cam timing), the exhaust side (an exhaust valve not opening, a blocked protective grating, high back-pressure), the turbocharger itself (fouled turbine, compressor or air filters) and the scavenge-air cooler. As a temporary measure the air receiver can be blown off to break the surge, but watch that exhaust temperatures stay within limits while the underlying fault is found.