[ngoma]

Unbolted the rear GP buss bar to check GPs #5 & 6 independently?

Battery strength? Starter? My starter had recently been going bad but gradually; it was hard to really notice the slower cranking speeds. Replaced the starter and Bang! Now it starts almost before I twist the key!

What is the battery voltage before energizing the GPs?

Injector line possibly a contributing factor-- how much is it leaking? From where?

Injection pump could also be a factor, esp. if the mainshaft seal leaks air into the IP while parked. Have a helper try to start it while you watch the transparent fuel line into the IP, watching for air bubbles.