Injector Pump Timing

Hi folks,
I have a 1999 L series and she recently kicked out the crankshaft oil seal. Needless to say it was one hell of a mess, but its all put back together and the timing marks are spot on, yet I'm having problems cold starting. Its producing unburnt fuel during cranking and I've replaced the heater plugs, heater rely and installed a heavy duty battery. I've been coming across posts about advancing the injector pump but for the life of me I have no idea how the heck this is done. Can anyone advise me on how to do this please?

on the fuel pump side of the camshaft, loosen the 10mm head bolts, and turn the pulley as far counterclockwise as possible in the slots of the pulley (don't remove the belt, as it's only half a tooth or so of adjustment usually needed)

Tighten the bolts back up, and give it a test