Operators' I was familiar with started 4, 3, 2, 1. All engines started in Low Grd Idle. #4 & 3 started using GSU and 2 & 1 using crossbleed. Two engines in Low idle or one in High idle provided enough air to Xbleed start the others. The Electra's I am familiar with had the GSU connection and a second GPU receptacle under the rear fuselage thus keeping the GSU operator well away from the #3 prop (the standard GSU connection was in the right wing root). The revised location for ground equipment connection also meant the aircraft could taxi away without removing the grd equipment if need be.