I have created an iron golem farm in a multiplayer server with raiding allowed. The farm is completely automatic, and kills the golems with lava. I am not having a problem with the golems spawning, they spawn. The lava is at their head level with water at their feet level to transport the drops. When they die, they only drop one poppy and no iron ingots. How can I fix this and make them drop iron? The farm works perfectly in single player creative mode.
Some servers restrict iron drops from iron golems to prevent the building of giant automated farms, or restrict any drops from environmentally-killed monsters, again, to prevent the creation of giant automated farms.
This might be done for gameplay reasons (no supplies of infinite free stuff) or for server lag reasons (no concentrations of hundreds or thousands of monsters collected in a tiny spot).
You may have to kill them by hand. Apparently there's a bug or change that makes mobs not drop the same stuff when they die as when they're killed personally, e.g., zombies won't drop iron unless you dispatch them personally, but only in SMP.
You might be able to change out the lava for a piston-based suffocator, timed so that it takes a fresh bunch of golems down to as few hearts as possible, then kill them by hand.
One reason the golems may not be dropping iron ingots is because you have to kill them yourself, kind of like XP, if you don't kill the mob, it wont drop XP. In this case, it's iron. Mojang probably did this to slow down or stop automatic iron farms. But you still can have a farm, just take out the lava, make it so you are out of their hitting range but they are in your range and make a room (if you don't have one already) where they will "wait" to be killed. They don't drown either by the way. You could use your huge amount of cobblestone from mining to make swords that you would specifically use for your iron farm.
Reducing their HP (I haven't tested this yet though)
You could take that lava and use it for the the same purpose but wont kill them you could make it where they fall through a 1 block (or 2) layer of lava before reaching the "waiting" room (if you did what I said above) this could reduce their HP enough to take only a few hits with a sword.