Posted: 8/19/2016 10:10:04 PM EDT
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Okay fellas.
I have a 20+ year old Craftsman chainsaw that doesn't work. I about yanked myself into cardiac arrest trying to start it and it it wasn't my wife's father's saw I'd have slammed it on the driveway about 50 times. Instead, I realized that I have only used it 2 times in 20 years that I've owned it and that the carb was probably in need of reconditioning. So I ordered a parts kit for the carb. When I took the carb off I realized why it wouldn't work. The gas line rotted,cracked and wasn't even hooked up to the carburetor. Anyway, I got the carb off, cleaned and reconditioned and now I am ready to do the repair on the gas lines into the tank. However, I'm a bit confused. There are two holes in the top of the tank: 1) The fuel line which had a filter on the end of it in the tank (this was the line attached to the carb). 2) There was a two sided connector laying in the bottom of the tank. One side clearly connects to a tube that goes through the second hole in the tank. But on the other side of the connector is a green rubber cover that has a duck bill like cover. The duck bill piece opens up, so I'm not sure if it is an air mixture thing or an unused gas return (but where does it return from?). The carb has only one connection to which a tube could be connected. Here's the manual (thanks Craftsman) that only shows ONE line going into the tank and omits the part I found in the tank all together. Craftsman sucks It does NOT have a primer bulb to explain the second line. Anyone know? I can hook the odd man out connector to a line and shove it through the extra hole but what do I connect the tube to? |
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Quoted:
Okay fellas. I have a 20+ year old Craftsman chainsaw that doesn't work. I about yanked myself into cardiac arrest trying to start it and it it wasn't my wife's father's saw I'd have slammed it on the driveway about 50 times. Instead, I realized that I have only used it 2 times in 20 years that I've owned it and that the carb was probably in need of reconditioning. So I ordered a parts kit for the carb. When I took the carb off I realized why it wouldn't work. The gas line rotted,cracked and wasn't even hooked up to the carburetor. Anyway, I got the carb off, cleaned and reconditioned and now I am ready to do the repair on the gas lines into the tank. However, I'm a bit confused. There are two holes in the top of the tank: 1) The fuel line which had a filter on the end of it in the tank (this was the line attached to the carb). 2) There was a two sided connector laying in the bottom of the tank. One side clearly connects to a tube that goes through the second hole in the tank. But on the other side of the connector is a green rubber cover that has a duck bill like cover. The duck bill piece opens up, so I'm not sure if it is an air mixture thing or an unused gas return (but where does it return from?). The carb has only one connection to which a tube could be connected. Here's the manual (thanks Craftsman) that only shows ONE line going into the tank and omits the part I found in the tank all together. Craftsman sucks It does NOT have a primer bulb to explain the second line. Anyone know? I can hook the odd man out connector to a line and shove it through the extra hole but what do I connect the tube to? Sounds more than likely to be the tank vent. Picture would help quite a bit, but based on your description that's what it sounds like. ETA: Does it look like the piece that's on the right side of this hose? 
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Probably a pressurization valve. The other end of the hose connects to somewhere on the exhaust such that each pulse of the muffler adds a tiny bit of air pressure to the fuel tank. This aides the carb in drawing fuel in. |
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Yep, looks exactly like a tank vent. Does exactly what others have said, pressurizes the tank allowing fuel to be pushed thru your other hose into the carb. |
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Quoted:
Yep, looks exactly like a tank vent. Does exactly what others have said, pressurizes the tank allowing fuel to be pushed thru your other hose into the carb. Quoted:
Yep, looks exactly like a tank vent. Does exactly what others have said, pressurizes the tank allowing fuel to be pushed thru your other hose into the carb. Where would that line attach? Other said the exhaust but I can't see any lines on the machine itself or in any of the diagrams. |
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Quoted:
Thanks fellas. I'll add this to the list of GD lessons learned! One last question does it likewise sit in the bottom of the tank or should I orient it right at the very top of the tank? Technically shouldn't matter; that's the point of the valve. It only allows air under pressure into the tank. When there is no pressure, the valve closes immediately (if still flexible and soft) and prevents fuel from going back up the line. FWIW, I would personally try to keep it some what higher in the tank based on when the saw is in it's normal operating position(s). keeping it from being submerged may help avoid any ethanol damage, which will cause it to dissolve/rot away faster. (I have no love for ethanol in gasoline, if you can't tell) |
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Quoted:
Where would that line attach? Other said the exhaust but I can't see any lines on the machine itself or in any of the diagrams. Quoted:
Quoted:
Yep, looks exactly like a tank vent. Does exactly what others have said, pressurizes the tank allowing fuel to be pushed thru your other hose into the carb. Where would that line attach? Other said the exhaust but I can't see any lines on the machine itself or in any of the diagrams. If there's truly not a single nipple or feed anywhere else on the saw, then it could have just been plumbed to the atmosphere. (outside the tank) This would allow the fuel tank to stabilize to neutral pressure, as the carb continually sucked fuel out using combustion vacuum. Without it, the vacuum that would build up in a water-tight fuel cell would eventuall cause a stall, since it would match the vacuum generated by the carburetor. If this is the case, unless you want sawdust in your tank, attach a tiny filter element to the other end that is outside the tank. (Simple fuel filter will work to filter the air going back into the tank via this tube) |