Have no way of refilling the fuel tank. Maybe I'm just dumb, but when I put an full one in the Chemical Laboratory it just empties it and trying to fill an empty one doesn't work. I'm using this with the Mekanism mod if that means anything. Just wondering if this is backwards. Haven't seen anyone else who had this problem.

I also can't find a way to fill fuel tanks or compressed air tanks either, would be really glad if someone explained how to.

@Sibith Fuel tanks need 250 mb of biofuel to be filled - I know for sure Industrial foregoing's works without issues.
@gustavoms00 You need to pump water in the chemical laboratory and give it RF, then put the empty compressed air tank and a piece of coal.

Just tried that that and it didn't work but it works for the bio tank so I think u may be confused

The bio tank needs water to fill up, not biofuel. If you don't have biofuel there's no way to fill the tanks. Does JEI show anything in the recipe for the filled tank in the chemical lab tab?

Oh there's my problem I need industrial foregoings to get liquid biofuel. I'll just trade it out with the mekanism mod. I have JEI and a recipe would never pop up but I guess this is why. I still think @pWn3d1337 should have mentioned that u need a mod that adds liquid biofuel or just make fuel tanks fillable without the requirement of another mod. Thanks so much!

No problem. I just noticed that you can also use Refined Fuel from Thermal Expansion in place of IF's biofuel.
You could easily use a CraftTweaker script to fill a tank, since they are simply two different items and not fluid containers, no need to avoid the mod just for that issue - something like this would work (shapeless recipe using bio mass):
recipes.addShapeless(techguns:itemshared:27, [techguns:itemshared:28,techguns:itemshared:61]);
Edit: I don't know how to make it so github keeps the brackets, so I reposted the script on pastebin

Oh thanks! That's seriously helps so much. I've heard of crafttweaker before and thought about trying it but I didn't know have. This helps a lot. I'll have to mess around with the script and get it work good. Thanks again!

Fuel tanks use fuel from other mods if it's present. If no fuel is present the recipe needs lava.

There's something wrong with the recipe script, apparently - You can place filled fuel tanks in the input slot and the chemical laboratory will proceed to give you back an empty fuel tank and 500 mb of lava

By the way, I just noticed that I posted this issue on the wrong issue tracker. Should I remake it in this one?

@pWn3d1337 Oh now I remember, I was messing with the config and did something with the lava fuel recipes thing not knowing what it did 😅 that helps alot. Thank you!

@pWn3d1337 actually tried fixing the config, but something is still very wrong. I want it to work with lava by default but messing with the config does nothing. Its the only part of the config that doesn't seem to work

I am experiencing the same problem. I have tested with only a few mods and there is no recipe listed for making a filled fuel tank. The Chemical Laboratory will not accept the empty tank either.

Forge: 12.2-14.23.2.2624
Chisel-MC1.12-0.1.1.26
CTM-MC1.12-0.2.3.12
Just-Enough-Items-Mod-1.12.2
techguns-1.12.2-2.0.1.1