Stihl bg85

[dig-dug-dan]

Mate is having problems with his blower

 It was running rough so had cleaned out the carb with an airline. Now the primer bulb won't prime but appears to be pushing air into the tank!  Any ideas?

[adw]

If it’s pushing just air into the tank then there Is no fuel in the carb to fill the bulb, so basically fuel starvation..

[dig-dug-dan]

11 hours ago, adw said:

If it’s pushing just air into the tank then there Is no fuel in the carb to fill the bulb, so basically fuel starvation..

Yes, but primer should pump fuel into carb, but it appears to just push air into tank instead.

[openspaceman]

6 minutes ago, dig-dug-dan said:

Yes, but primer should pump fuel into carb, but it appears to just push air into tank instead.

No the purge bulb sucks fuel through the carb and returns it to tank

[pleasant]

If the return is emitting air back into the tank it must be 'sucking' air in through the fuel pick up...otherwise if it wasn't then you would create a vacuum and the primer bulb would depress and not return once any air in the system has been expelled. If you are sure it is expelling air back into the tank then it must also be sucking it in from the pick up. If not then it doesnt make sense as the air in the primer bulb has to be coming from somewhere.

 

Have you hooked out the pick up pipe in the tank, removed the fuel filter from the end and whilst pressing the primer put you tongue over the end of the pick up pipe....logically you should feel your tongue being drawn into the pipe under light pressure.

 

If not and you are adamant it is still expelling air back into the tank and the primer appears to be operating as it should, then it may have a small pin prick hole in it, which is small enough to be sealed with your finger when primed hence why it still appears to work

Edited June 24, 2023 by pleasant