Question about Garden
525 jonsered chainsaw, wont run unless, fuel is dropped down the head, stays going for a few seconds, then shuts off. Just cleaned the carb top to bottom and it is the same as before, blew out all the jets and is spotless inside and out but still the same. Replaced all lines including gas line, carb is sucking gas, and the gas tank is clean and full so I dont know what else that it could be. If you have any help it would be great. Thanks
Was carburetor cleaner used to blow through the fuel circuits?
Small engine carburetors have tiny polymer or woven Teflon discs that move back and forth within the check valve(s). Carburetor cleaners or dip solutions are not intended for this type of component. The only approved cleaner that I have heard about is non-flammable brake cleaner, like Brakleen. Stihl's tech department recommends this approach to prevent damage to soft components of the fuel system.
It sounds like you are seeing fuel in the metering chamber, so the likely fault is a check valve, especially since this saw may be approaching 30 years of age. It is also important that the impulse passage/line is pulsing properly.
If there is a tiny hole in the intake that matches a hole in the gasket and carburetor, this is an impulse passage. Remove the carburetor, place a drop of oil on the hole in the intake, and turn over the engine. It should draw and expel the oil as this is attempted a few times. I'm not familiar with your saw, but some designs have an impulse hose that attaches to the carburetor's pump cover. I seriously doubt this is what you have, but it can also be checked using a few drops of oil.
The alternation of positive and negative impulses moves the metering diaphragm back and forth, allowing fuel to enter the metering chamber. If the impulse is weak, it may enter too slowly for the engine to fire. If the impulse can be seen repeatedly with the test above, it should be fine to operate the carburetor.
Next, the high speed nozzle needs to be checked with brake cleaner. It should allow a large stream to be blown into the throat of the carburetor from the metering chamber (if the high speed nozzle has a visible hole on top) or by removing the high speed mixture screw and spraying into the seat. It should not allow any cleaner to be blown the opposite direction. This can be tested any most Zama and Walbro carburetors by bending the red nozzle that comes with the cleaner. I usually feed it through the hole in the center of the fuel pump side until it touches the nozzle's outlet.
If the nozzle fails either test, it needs to be punched into the bore to remove it. A new one is simply oiled and punched into place at the same height, but finding this one may be tough. I was unable to find any information about this saw in a quick search.
The carburetor will probably have a model number stamped into it, and that will help to find if parts are still available.
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Posted on Jan 02, 2017
SOURCE: poulan 2000 starts but wont
Two common things are a clogged filter which is usually on the end of the "fuel finder" hose within the fuel tank snd the other common problem is failure of the fuel pump and or check valves. The latter is in the carb and consists of a small diaphram that is driven by vacuum pulses picked off a port in the carb. The check valves of the pump are jsut little flaps. The fuel pump problem is most likely if you have always used clean gas. The fuel pump diaphram seem to be good for about 2 years then it is carb rebuild time. It takes less than an hour to rebuild with new kit. Try not to disturb adjustments and idling screws.
Posted on Oct 22, 2010
Find the gas/air adjustment screws on the carb (next to the the throttle cam where the throttle cable attaches. Turn the screws in all the way... GENTLY... Those are needle valves, and too much torque on them will damage the needle valve seats. turn both of them out one and a quarter to one and a half turns. Start the saw, and adjust one or the other screw in or out until the saw runs properly. If there is a plastic stop installed on the screws, remove it first, and replace it after the saw is running properly. You have to be patient while tuning the carb as it may take a while. If you adjust too much and the saw refuses to start at all, start over with the 1-1/4 to 1-1/2 turns out on the screws.
Posted on Aug 19, 2012
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