Chain saw not sucking gas

[Hokiefyd]

I have a Poulan chain saw I'm repairing for a buddy at work. The fuel line cracked (was old and brittle) and he was going to take it in, but I said I'd fix it for him. The line runs up through the handle (PITA design) into the carb, but I got a whole new line put on. The trouble I'm having is it won't suck the gas out of the carburetor. There is a fuel filter canister on the end of the fuel line, but I believe that's good because the fuel line is full of fuel up to the level in the tank...meaning fuel is getting through the filter. I just can't find a vacuum enough to get the engine to suck it out of the tank.

The engine runs if I pour gas down the carb, but it won't suck it from the tank. The line is empty. The gas cap seems to leak through the air vent, but I believe that since the fuel pick up is completely submerged, the carburetor SHOULD suck that gas through, shouldn't it?

Thanks in advance,
Jason

 

[Curious Kid]

Jason,

I had a similar problem with my father's chainsaw that had been rarely used. The only way I could get it to fire up, albeit for a second or two, was to spray wd-40 down the barrel of the carb. It just wouldn't pull gas from the fuel tank.

Because the engine isn't stationary and is operated in just about any position like a gas line trimmer and hedger, the carb. has no float bowl. The reason being is that every time the engine would be tipped, fuel would flow out into the engine, stalling it, and out through the filter, with the float valving remaining open allowing continued fuel flow...a hazardous situation.

What's the design solution that was devised? - a diaphram that seems to funtion both as a vacuum actuated fuel pump and fuel valve actuator. It's been some time since I made the repair I can't clearly remember the specifics of operation. In any case, it sounds like you need to purchase a simple carburator repair kit for that specific model ( I ordered my through NAPA), which will consist of a new "fuel metering" diaphram and other gaskets that the card body may require. And to note, I also found varnish deposits in the card meterways, so after cleaning and assembly, I ran some techron fuel system cleaner for several tankfulls. I am happy to report that after a few pulls, the saw started right up, and after some tweaking of the metering jets, it runs great and idles without bogging out.

Good luck

 

[Hokiefyd]

Thanks very much! Yeah, it acts like the "fuel pump" isn't working...and I guess in this case, the "fuel pump" is a diaphram, since you're right -- it's not a gravity feed (like a lawnmower for example). I'll look into a carburetor rebuild kit.

Thanks!