Ok, when I start cooking something in my custom furnace block, and I log out while there is still fuel. Next time I log in, the fuel resets to max, So its infinite power, and just to make you you understand. It is not duplicating the fuel item, the fuel bar just keeps going to max. I don't know which classes you would need to look at, so please let me know and I will post them. Thanks

Are you saving to NBT?

Are you saving to NBT?

If this is what your talking about, then yes

public void readFromNBT(NBTTagCompound p_145839_1_)
    {
        super.readFromNBT(p_145839_1_);
        NBTTagList nbttaglist = p_145839_1_.getTagList("Items", 10);
        this.frierItemStacks = new ItemStack[this.getSizeInventory()];

        for (int i = 0; i < nbttaglist.tagCount(); ++i)
        {
            NBTTagCompound nbttagcompound1 = nbttaglist.getCompoundTagAt(i);
            byte b0 = nbttagcompound1.getByte("Slot");

            if (b0 >= 0 && b0 < this.frierItemStacks.length)
            {
                this.frierItemStacks[b0] = ItemStack.loadItemStackFromNBT(nbttagcompound1);
            }
        }

        this.frierBurnTime = p_145839_1_.getShort("BurnTime");
        this.frierCookTime = p_145839_1_.getShort("CookTime");
        this.currentItemBurnTime = getItemBurnTime(this.frierItemStacks[1]);

        if (p_145839_1_.hasKey("CustomName", )
        {
            this.field_145958_o = p_145839_1_.getString("CustomName");
        }
    }

    public void writeToNBT(NBTTagCompound p_145841_1_)
    {
        super.writeToNBT(p_145841_1_);
        p_145841_1_.setShort("BurnTime", (short)this.frierBurnTime);
        p_145841_1_.setShort("CookTime", (short)this.frierCookTime);
        NBTTagList nbttaglist = new NBTTagList();

        for (int i = 0; i < this.frierItemStacks.length; ++i)
        {
            if (this.frierItemStacks[i] != null)
            {
                NBTTagCompound nbttagcompound1 = new NBTTagCompound();
                nbttagcompound1.setByte("Slot", (byte)i);
                this.frierItemStacks[i].writeToNBT(nbttagcompound1);
                nbttaglist.appendTag(nbttagcompound1);
            }
        }

        p_145841_1_.setTag("Items", nbttaglist);

        if (this.hasCustomInventoryName())
        {
            p_145841_1_.setString("CustomName", this.field_145958_o);
        }
    }