Attempting to Start up one of ADL's 'finest' Enviro400's DK64BVE with a master reset 

If an engine starts up easily and straight away then chances are that it is well looked after. Normally the better the maintainace, the less likely there is to be problems. Unless the engine or the vechicle in general is poorly manufactered and has problems regardless of how good the maintainace is.

@@Joshwoakes Buses back in the day were nice and were properly looked after. Arriva don't have a good track record for maintenance.

​@@jaggass I see you everywhere on Elton john and bus cids micheal

Couldn't beat an Atlantean

because the master switch was turned off

My guess is because is that starting an engine often requires alot of power to do so. The lights also require some amount of power to be lit, so having them on can make it so there is too little power to start the engine properly especially if it's cold and the battery is weak in general. So the lights are usually turned off in the hope that the engine will then have the power to start up. Not mention like what mrpolishbanana said the master switch was turned off, meaning the lights would have shut off anyway. However if the lights are controlled by the bus's computer system then turning off all power may reset the status of the lights to "switched off state", meaning that'll you have turn them back on again. It's similar to what can happen in a car with a weak battery. if you have too many lights on or too many electrics on with a weak battery, it can make it harder or impossible for the engine to start.