C1Q S93 carb-Total clean,new welch plug(oblong) and new Kit--Won't pull gas into primer unless I let fuel level cover return line to tank.New carb on order $32 but is it the primer block is bad ?$21 for that so I wasn't going to try that.Just would like to learn.Thanks David
Zama Question
- Thread starter kuhndog
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Thanks..Next week when the new one arrives and I remove this one I will look in that block,I know it also had a welch plug and got to see what's in there.
A cycling diaphragm type pump normally needs two check valves to work properly. This applies to the fuel pump inside the carb as well as the purge bulb type pump on the outside. If these do not operate, the engine can suck air back through the purge line.
The purpose of the fuel bulb pump located on some chainsaws is to merely suck fuel all the way through the carburetor including the pump and metering chamber sections in order to eliminate or purge the air. The bulb pump does not squirt fuel into the engine or prime the engine.
The purpose of the fuel bulb pump located on some chainsaws is to merely suck fuel all the way through the carburetor including the pump and metering chamber sections in order to eliminate or purge the air. The bulb pump does not squirt fuel into the engine or prime the engine.
dswensen
ArboristSite Guru
Not trying to be a wise-ass, but I have to ask. Do you have the fuel lines coming from the tank connected backwards?
I feel I don't but I think owner played before he asked me.Lines are formed one short ,1 long.Short is the infeed (with filter)connected to pump side,Long hose on higher fitting which is primer block on metering side of carb.I did not switch them because this seems right .#2 Once bulb does have gas in and line is off it sprays gas out like that is return to tank #3 might be hard also to get line (Short) up to higher fitting.
bikesandcars
ArboristSite Operative
Like said above, Zama carburetors use the "punch bowl" to circulate fuel through the carburetor, not to inject it like an accelerator pump. The purpose of the primer assembly is to circulate new fuel through the carburetor and to eliminate air, aiding in quick starting.
The check-valve on the return spiggot coming out of the fuel bowl area allows air and fuel to return the tank (or on the ground in some models), but does not allow fuel (under pressure from the tank) to flow back through the fuel circuit. The other check valve in the primer assembly blocks reverse flow when pushing the diaphram allowing the pump to operate. I believe there is also a 3rd check valve inside the fuel circuit.
If your return check valve was broken you would flood the saw with excess fuel coming from the tank, but that wouldn't cause fuel to come out of the check valve all the time. Sounds to me like it could be one of the diaphrams, which you would need a carb gasket kit to fix.
A simple light "blow" on the return hose will tell if the check valve is shot, if you can push air past it the check valve is faulty, don't blow too hard or used compressed air. Better to do this off the carburetor.
Can you post a picture of the carb and hoses in current configuration?
The check-valve on the return spiggot coming out of the fuel bowl area allows air and fuel to return the tank (or on the ground in some models), but does not allow fuel (under pressure from the tank) to flow back through the fuel circuit. The other check valve in the primer assembly blocks reverse flow when pushing the diaphram allowing the pump to operate. I believe there is also a 3rd check valve inside the fuel circuit.
If your return check valve was broken you would flood the saw with excess fuel coming from the tank, but that wouldn't cause fuel to come out of the check valve all the time. Sounds to me like it could be one of the diaphrams, which you would need a carb gasket kit to fix.
A simple light "blow" on the return hose will tell if the check valve is shot, if you can push air past it the check valve is faulty, don't blow too hard or used compressed air. Better to do this off the carburetor.
Can you post a picture of the carb and hoses in current configuration?
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Sorry can't do pictures.Bad enough typing.But now I under stand problem,not even removing carb but pulling return line and hooking up a piece of hose I can easily blow into primer bulb.Then i removed hose pushed down primer (fuel came out)blocked off that fitting with finger and primer filled.I bet owner blew both fittings out blowing the check valves Thanks much
