I used to not bother depressurising the fuel system,just used to let it spray out until the pressure dropped.Then one day while doing this,I got petrol sprayed in my ear.Getting petrol in your eyes is absolute bliss compared to getting it in your ears,I thought Id have to go to hospital it was that bad for a while,I just kept running it under water for about an hour,it came good,but it was sore for ages.Anyway I learnt my lesson,the hard way as usual.Depressurise the fuel system first.