Yanmar Injector Pump

[Jacana]

diagram.pdf
Need advice please to fix fuel leak on Yanmar 3gm30. Originally supposed to be a 2 hour job to replace the O rings. Mechanic took all 3 delivery spring holders out replaced o rings put all back together then started the engine after a lot of priming it started and screamed to max. revs. Caused a bit of panic and he eventually shut down the engine. Said the cause was that the fuel rack must have moved. After an hour of trying to fix it he said he might have to take the pump off to get to the fuel rack. He rang the workshop and they told him not to remove the pump, however after another hour of tinkering said he couldn't realign the fuel rack so will have to take off the pump. After another hour he said he couldn't get the pump off and maybe the fuel rack moving has stopped it coming off so will go back to workshop, check the manual and come back tomorrow and try again. So far 5 hours and no fix.
Want to know if fuel control rack can be realigned without removing pump and also how to stop rack moving in future when replacing the O rings. See attached diagram for further detail.
Thanks Geoff.