This mod replaces whole definition of wooden-chest and small-electric-pole so some properties might get lost, namely inventory_move_sound, pick_sound and drop_sound.

https://github.com/wube/factorio-data/blob/2.1.21/base/prototypes/item.lua#L224-L226
https://github.com/wube/factorio-data/blob/2.1.21/base/prototypes/item.lua#L378-L380

You can modify only the necessary properties instead, preserving the rest of the existing definition and making the mod more robust against future changes in the base game

local fuels = {
  ["wooden-chest"] = "3MJ",
  ["small-electric-pole"] = "0.75MJ"
}

for name, fuel_value in pairs(fuels) do
  local item = data.raw.item[name]
  item.fuel_categories = {"chemical"}
  item.fuel_value = fuel_value
end