Zama Carb Priming Air Instead Of Fuel.

Joined
Sep 10, 2005
Messages
1,829
Location
Erie, PA
This happens all the time especially on poulan / craftsman equipment with zama carbs.

Nothing is visually wrong and carb is absolutly pristine.

I connected brand new fuel lines, and brand new primer bulb, and ran the hoses into a coffee can with fresh gas. The gas leaving the carb is very bubbly and mostly air. None of the gaskets on the carb are leaking. What causes this?

Hose routing: New hose from can to inlet side of carb. New hose on outlet side of carb, connected to suction side of primer. Hose connected to outlet of primer into the can.

Yes I know an aftermarket carb is $15-18 bucks but the linkages do not work, and the low jet is mostly un-tunable. Trying to fix the OEM carb.

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Did you change the lines one at a time? What was the original problem prompting you to change the lines?
Every time I seen that, it was either incorrect line routing, a blockage in the carb or an air leak (poor fit for the lines) somewhere. I never seen a gas cap cause it but I guess in theory it could.
 
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Do the lines fit tight? If the line is the wrong size I.E. too big, it will suck air around the connections.

Do you have the primer bulb plumbed in the correct direction ?
 
One possible cause would be winter blend fuel being used in a warm shop. Butane content is higher and it might be boiling off.
 
Does it have a choke? If there's a choke that is what is supposed to get extra fuel into the engine. The primer circuit is to bring gas up from the tank through the pump to the metering chamber of the carb. When the bulb pulls fuel out of the metering chamber it also pulls in some air backward through the jets.
 
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