Won't start with air filter in

[JonnyTeaches]

Looking for some help. I've got a Craftsman self-propelled mower that won't start with the air filter attached. I've got to blow some air into it with my compressor to get it to fire up and then it will get up to full throttle. The spark plug and oil are new, I changed them about two months ago and I know there is fuel getting to the spark plug because I removed it and it's got some moisture on it. Any help would be appreciated, trying not to buy a new mower.

 

[upupandaway]

So you blow compressor air into the carb and it starts?
I think what that does is create a greater than normal vacuum in the carb venturi thus it starts.
That would mean in the carb some crud is making it harder for the fuel to flow up as it should.
Post a model # or a pic of the mower as different makes have different ways\parts to clean out the carb.

 

[JonnyTeaches]

So you blow compressor air into the carb and it starts?
I think what that does is create a greater than normal vacuum in the carb venturi thus it starts.
That would mean in the carb some crud is making it harder for the fuel to flow up as it should.
Post a model # or a pic of the mower as different makes have different ways\parts to clean out the carb.

No I'm blowing air from the compressor into the port where the air filter is. I unscrewed the carb a bit at the base and gas started coming out right away so I thought maybe the carb was okay? THe model # is 917.374150

 

[upupandaway]

so you blow air here that i circled or else where?
If yes, then as i said before. The screw at the bottom of the carb bowl also acts metering fuel. Pinch the fuel line, take out the screw and with a needle and or carb cleaner clean out the small hole on the side and the 2nd hole on top.

Just because there is gas in the bowl does not mean it will be pulled up into the venturi if the passages are dirty.

 

[JonnyTeaches]

so you blow air here that i circled or else where?View attachment 53533
If yes, then as i said before. The screw at the bottom of the carb bowl also acts metering fuel. Pinch the fuel line, take out the screw and with a needle and or carb cleaner clean out the small hole on the side and the 2nd hole on top.

Just because there is gas in the bowl does not mean it will be pulled up into the venturi if the passages are dirty.

Yes that's where air is being blown into. I unscrewed the bolt at the bottom of the carb bowl and cleaned that out and even sprayed in some carb cleaner. I was able to get it running again but had to again use the air compressor, once it got going it was fine but again wouldn't start without that assistance. I also replaced the spark plug as well.

 

[Mower King]

I'd say your primer is not working, that is how you get a small shot of fuel in the venturi, thus easy starting. That kind of set-up is real finicky to get to prime right. The gasket just behind that plastic housing has a super small slot in it to pump a shot of air through a small passage in the carb, priming the carb with raw fuel and, it has to be aligned just right for the primer to work. I'd check into that.