Jonsered 670 carb

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mountainlake

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It's not pumping enough fuel, cleaned the carb a couple of times, new fuel line, new impulse line, diaphrams seem good. It has a tilitalson carb with 3 lines coming to it, fuel line, impulse line and another running to the tank. What is the purpose of the 3rd line, can that cause it to not pump gas to the carb. It will start and idle a long time but if held wide open gradually leans itself out, also the high adjuster wont make it run rich at all. Steve
 
It's not pumping enough fuel, cleaned the carb a couple of times, new fuel line, new impulse line, diaphrams seem good. It has a tilitalson carb with 3 lines coming to it, fuel line, impulse line and another running to the tank. What is the purpose of the 3rd line, can that cause it to not pump gas to the carb. It will start and idle a long time but if held wide open gradually leans itself out, also the high adjuster wont make it run rich at all. Steve

First thing I'd check is the final fuel filer screen in the carb itself...it's located under the top cover. Don't even have to remove the carb, it's located in a 5/16" hole right where the fuel enters the carb... If this get clogged it will make the saw run exactly as you describe.

The third line is a return line to the fuel tank. The idea is when the engine is not using a lot of fuel like when winding down but is still pumping due to the rpm the unused fuel can return to the tank and not pressurize the carb and dump extra fuel into the engine. Part of an emissions/fuel economy theory.....
 
It's not pumping enough fuel, cleaned the carb a couple of times, new fuel line, new impulse line, diaphrams seem good. It has a tilitalson carb with 3 lines coming to it, fuel line, impulse line and another running to the tank. What is the purpose of the 3rd line, can that cause it to not pump gas to the carb. It will start and idle a long time but if held wide open gradually leans itself out, also the high adjuster wont make it run rich at all. Steve
Also don't forget to check the fuel filter, if you haven't already. Also, if the fuel tank is full while these symptoms show themselves, try dumping most of the fuel out, then restart the saw and see if symptoms change. If the saw will run WOT longer, you likely have a plugged fuel tank vent.
 
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