There does not appear to be a primer bulb on the Stihl BR400 that I can see in the exploded parts.
You will probably have to go to the dealer. Stihl will not share Manuals or parts list with anyone but the dealer. You pay a lot for a Stihl and you continue paying as parts are not interchangeable with anything else.
A cracked primer bulb. You will need to replace it.
No gasoline is reaching the primer bulb.
primer bulb replacement on craftsman 32 cc week wacker
Don't know that a leaking primer bulb can be repaired. Most likely, you have to replace it. You don't want to forget the routing of the fuel lines!! You might want to make a drawing of the routing before you remove the primer bulb.
There is an orifice in the primer assy. in the carb. that is plugged. You will have to remove and clean the primer assy.
The start primer rubber bulb must be cracked/damaged. Replacement parts are available.
It sucks gas from the gas tank to the carborator using nothing but suction In general the primer bulb draws fuel from the tank through the carb and then returns it to the tank. Look for "carb" and "tank" on the primer bulb and make the respective connection. A line should come from the tank to the carb. Another from the carb to the primer. and another back to the tank.
look on youtube lol
cracked gas line, cracked bulb, or weedeater out of gas
Connection nearest bulb is return to tank.
Because it probably has a crack or a hole in it.