Primer buttonwont let fuel in

If hadn't changed the fuel lines prior to this problem it is probably the internal filter screen in the carburetor plugged or the tank's fuel filter.
If you had replaced the fuel lines then it is probably the plumbing of the fuel lines. The primer is suppose to suck through the carburetor and return the excess fuel back to the fuel tank. It fuel system plumbed backwards, which can be done several ways, the carburetor internal check valve will prevent proper operation of both itself and the primer.

Not sure if your primer bulb is on the carb or separate but here are some basics... The smaller line is the main fuel line. It has the fuel filter on it and the filter should be laying on the bottom of the tank. That line goes to the fuel pump side of the carb ( usually the inlet near the center of the carb body ). The fuel goes through the filter up the main line and fills the carb then to the primer bulb whether its on the carb or separate. If on the carb the spigot closest to the primer bulb takes the larger line and returns to the tank. That line should go into the tank about half an inch and terminate. If the primer is separate the larger line leave the carb from the spigot on the metering side ( usually close to the edge of the carb body) to the inlet of the primer bulb then from the primer bulb out ( usually center of the bulb) to the tank and terminates about half an inch inside the tank. Remember... fuel filter into carb, carb to primer bulb, primer bulb to tank. If the fuel does not go that direction when the bulb is primed then you have lines hooked up backwards.

This particular JD engine has an individual fuel pump for each cylinder. The injectors, fuel lines, and pumps are not accessible from outside of the engine. There is a hand primer pump built into the top of the fuel filter. Start by removing the rubber outlet line from the filter base and pump the primer pump until fuel come out of the filter base outlet. Ounce fuel comes out of filter reconnect the line and continue pumping by hand until the pump button feels solid, then crank engine until it starts. This works better if a helper is available to operate the starter while continuing to pump the hand primer. This is normally all that is needed after running out of fuel.

If fuel does not come out of fuel filter base there may foreign material inside of primer pump. Primer pump can be disassembled and cleaned. If fuel comes out of filter, primer pump become feels solid but engine does not start the fuel control rack inside of engine may be sticking in the off position. This may sometimes be overcome by clicking the key switch from off to on rapidly. If not you may have to have your dealer remove the governor cover to free the rack.

You either need a new primer bulb (leaking air) or you have the fuel lines routed wrong. Here is the correct fuel line routing just in case:
Small diameter line out of fuel tank (has filter in-tank on end) connects to the side of the carburetor that has the fuel pump....that is the cover without the hole in it. Other larger diameter fuel line out of tank connects to the longer nipple on the external purge/primer bulb. The bulb "pulls" fresh fuel from the fuel tank to the carb and then out of the carb to itself, where it then pushes any air/old fuel back into the fuel tank. The remaining larger diameter fuel line in this setup goes from the metering chamber (has cover with writing on it and a vent-hole) side of the carburetor to the smaller nipple on the purge/primer bulb. Again, on the primer bulb, the longer nipple has a line going directly from it to the tank. The shorter nipple on the bub has a line from it going to the metering chamber side of the carb.If the purge/primer bulb is on top of the carb...small line from carb body to small hole in tank with filter. Larger diameter line goes from the bulb on the fuel pump side of the carb to the larger hole in the fuel tank where the line is held in place with a nylon nipple connector that keeps the line from pulling out of the tank

The small diameter fuel line that has the fuel filter in the tank on it goes directly to the carburetor (with the built-in primer or externally mounted primer). IF the carb has the external primer, the small line goes to the nipple on the carburetor opposite the end with the hole in the cover. If it has the built-in primer on it, it goes to the carb body on the nipple furthest from the bulb. The large diameter line is the fuel return line and if the carb has the bulb on it, this line connects on the nipple closest to primer bulb.. With the externally mounted primer, this line connects on the longest nipple coming out of the primer and goes to the fuel tank (not the filter though). There is a nylon connector inside the tank that holds this larger line in place. The shorter nipple on primer bulb has a smaller diameter fuel line connected to it and connects to the nipple on the carb closest to the end with the hole in the cover. Built in primer has 2 fuel lines...externally mounted has 3.

It should be as illustrated on the link.
Typical Fuel System (Primer Bulb and fuel lines may not apply)
http://www.fixya.com/support/r3706813-2_cycle_fuel_system_repair
The line with the filter needs to be long enough to reach all parts of the tank as the saw is moved. The return line is not a critical length probably mid tank. Do you have the filtered hose feeding the primer and not the carburetor? That will cause what you describe. HTH
Lou

I'm assuming a 2-stroke engine. Does the fuel system have a primer button? Assuming that the answer is yes, the carburetor is not pumping fuel, but starting on the primer charge. Is the carburetor a Walbro brand? If so, got to: http://www.drystacked.com for a 12 page PDF on theory and repair of these carburetors. If the primer works, the main fuel line should be ok.

defective check valve pull the tank and remove the fuel line replace the small inline filter on hose.

There is two sizes of line. I see the large one goes to the large port on the primer button and then to the fuel tank. The small one goes from the primer button to the carb. The problem is there are two hose connections on the carb. I believe one is a vent, but I am not sure what one it is. I have a 36cc 2-cycle model 358.352161

You prime it at the lifter pump on the drivers side the primer is a black rubber push button type. you shouldn't have to crack any injector lines if you do you can risk damaging the lines or their ability to seal. good luck