I cannot get inserters to grab off of belts

[superstewie]

I'm trying to automate power. This is my first time playing the game. I have tried and tried and tried. Watched video after video of 0.16 and I cannot figure out what I am doing wrong. I cannot get these basic electric inserters to insert coal off of the belts into the boilers no matter how low the boilers are on coal, or no matter how backed up the belts are or on which side they are backed up on. Is there anything I'm missing?

[Koub]

Your save would be helpful, can you attach it to your post ?
btw : we're not at 0.16 yet Current version is 0.15.34

[Nexela]

Inserters will only insert as much items as it needs to keep the target running for a short time. This is to prevent one machine from taking all of your items.
From your picture it looks like you boilers already have some fuel in them. Additionally If they have something besides coal in them they will not insert coal until the previous fuel runs out.

[ItsDarthChaos]

As said above, Inserters only take what is necessary. They will take the materials necessary for two additional processings after the one in progress. Meaning when your boilers are on their last coal, it will have two in stock. If you have an assembler making gears, it will keep 4 iron plates in storage, which is what is necessary to make two more gears.

[5thHorseman]

Also, yellow inserters only work when there is power. Which you're using them to generate. This could lead to a catch-22 where you need power to make power, but don't have any power.

I suggest using the black burner inserters on steam power plants. They (almost) always work so long as there's coal available.