My Stihl BG75 blower problem sounds similar. I very carefully rebuilt the carby last year, but didn't solve the problem.

When I press the bulb, air bubbles go into the tank. When I release the bulb, no fuel is being pulled into the carby.

I will be eagerly monitoring you post for good info.

 

Recently replaced the primer bulb on my Stihl trimmer (old one had cracked and was leaking). I replaced the fuel that was leftover from last season (unfortunately!), have pulled the fuel lines and blew them clean, also blew the feed lines on the carb / primer clean as well. The darn thing still will not prime (no fule in the primer bulb).

When you push on the primer, you are pulling fuel from the tank, threw the carb and then back into the tank. I would start simple,check the fuel line for any kinks, then on to replacing the fuel filter in the tank. If that does nothing form you, then it's on to the carb. You can try to clean it, with carb cleaner with the little straw, but you have to take it apart to do that, if that works for you great. If not, you can get a kit to rebuild it. Personally, I don't bother rebuilding carbs any more, less aggravation to put a new one on.

Good Luck

 

Are sure you didn't happen to reverse the two lines to the carb. If you did, the return line to the tank from the carb will not likely be in the fuel and will only pull air from the tank to the carb. If the lines are properly installed and the fuel filter has free flow, about the only thing that will prevent the primer bulb from operating is a faulty check valve in the portion of the carb immediately below the primer bulb. This check valve can be easily damaged if you blow high pressure air through this portion of the carb.

Dutch

 

The check valve in the carb is stuck, I normally put the hole carb in my high temp parts cleaner and it will free it up and work like new. Otherwise you will probalby have to replace the carb. Should only be about 60 bucks.

 

Thanks so much for the responses guys!!!!

I did pickup a carb rebuild kit ($12) and was going to go that route, but I'll try soaking the check valve first and see where that gets me. The potential for damage part makes me a bit nervous, as I did (gasp) attempt to blow it out using a drinking straw and some deep breaths. Hopefully I didn't screw it up.

I did check the fuel lines and they are routed okay, the filter appears to be clear / clean as well.

I'll keep everyone posted, thanks again!

 

can you get a carb rebuild kit at any hardware store??

 

can you get a carb rebuild kit at any hardware store??

Not sure, Went through my local Stihl dealer. It's a Zama carb, so they're probably more widely available.

 

I see that this chat is quite old buy hopefully this will help the next guy from spending hrs on trying to figure out why the primer bulb won't prime! I too spent hours trying to figure this out having eliminated that it was a cracked bulb, bad fuel line, bad diaghram, bad carb, etc. I was almost convinced to spend the $50 on a new OEM carburetor. However after after some careful thought I removed the primer bulb base and figured out out that the 2 holes in the primer base are actually valve inlets. These inlets become clogged much like a fuel filter. The answer to this problem is to take some thin gauge Christmas tree ornament wire but wire and rheem out the 2 bulb base inlet holes to remove the dirt and gunk that is clogged up within the plastic bulb primer base. Spray in some WD40 or carb cleaner into the holes and the primer brass inlet tube. Reassemble and she primes like a screaming banshee. I searched and searched all over the internet and could never find any info on this....sometimes you just need to think through things logically...in this case I figured there was nothing magical about the primer base....just another point for dirt and gunk to magically accumulate!