Speaking of hard starting, the old P&W JT3D (B707) had a problem at high altitude airports such as Mexico City, Jo-burg, Tehran etc to get a light off. The burner pressure, Pb, generated in the burner section during start was not high enough to open the FCU fuel valve so no start. P&W in a lovely piece of engineering cut the Pb line from hot section to FCU and teed off a pipe to the drain cluster. This pipe was fitted with a tyre valve core and a metal valve cap. To start, the ground engineer would remove the valve cap and connect a bike pump to the pipe. As the engine wound up on the starter you pumped like crazy and usually there was a thump and she lit off. Then disconnect, refit valve cap and move to the next engine.
I often wondered what the pax thought when they saw a guy pumping up the engine with a bike pump. FE used to do it at some ports when the engineer who was trained was away. I did a few coz I really didn't want any untrained people that close to a running jet engine.