I have a craftsman string trimmer, 358 798 271. Do you have a diagram, or can you explain how to hook up the fuel lines, primer bulb, and carb? Thanks.

Hi and welcome to FixYa, I am Kelly.
The fuel line WITHOUT a strainer will go from the tank to the OUTSIDE primber bulb connection then from the primer bulb center connection to the carb. Item 7 this link comes with the diagrams:
http://www.searspartsdirect.com/partsdirect/part-model/Craftsman-Parts/Grass-trimmer-weed-wacker-Parts/Model-358791072/0247/1503820/P0808034/00002?blt=06&prst=0&shdMod=358791072

There are several you tube videos here on replacing fuel lines:
(do not delete)
Something to note... inside the tank there is a fuel filter/strainer. Make sure to replace that fuel line also. The connection from the strainer will connect straight to the carb fuel mainfold connection. The center connection of the primer bulb will go straight to the carb fuel manifold.

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Thanks for choosing FixYa,
Kelly

Chances are the primer bulb is hooked up backwards, I did that once, made me feel pretty foolish.

Hi There, Check the primer bulb for tare or pin holes. Replace it. Check and clean carb jet it maybe plugged with debree. Also check for spark which you didn't say. Replace with correct plug.
Note; Do not use strong cleaners on rubber seals (O rings and gaskets) They dry up and crack.
If needed use a dabble of grease on seals

This is an ongoing issue for users, and rightfully so. 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. Years ago on 2-stroke trimmers, primers were not even used,...you choked the carb with a slide lever and gravity let fuel enter the carb from above...a few pulls, a "pop"...slide it off of choke and away you went.
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.

Usually the line with the filter on it that comes from the tank goes to carb. inlet first which is most likely close to the bottom side of the carb.nearest to the engine,then the outlet or return line on the carb.goes to the inlet side of the primer and the outlet side of the primer goes back to the tank. The primer draws fuel through the carb to the primer to the tank if its not? then correct the line connections until it does

The Walbro has two connections on it for the fuel line. My Walbro has one connection on the side of the idle screw and main fuel adjusting screw. This connection hooks up to the suction side of the primer bulb. Usually the shorter stem. (You actually **** fuel through the carb instead of pushing it through.) On the other side of the carb is the other hook up. It draws fuel from the tank. This line will connect to the side of the tank that has the filter. The other side of the tank is your return and it hooks to the other connection on the primer bulb. Usually the longer stem.

ok If you have a Walbro WT series carb "without" a built on primer bulb here it is. First off if the fuel lines disintegrated you MUST disassemble it and clean it out. The MOST infintesimle speck of gas line trapped, can allow good prime and bad operation. OK? Don't be lazy on this. Just be delicate removing the flaps gasket and diaphram. ZAMA GND-12 Is the replacement Gasket and diaphram kit fot that carb. Use a cleaner, compressed air or blow good thru it. OK Now...Primer bulb, Carb, and Fuel tank, re connects: Smaller Diameter line comes from Gas tank (Connect filter screen to this in tank) to the short Straight brass carb connector. Primer bulb suction goes to the bent carb brass connector. If small line brings fuel "in" this other line sucks it back "Thru the primer bulb" and the blow side of the primer bulb sends it back to the fuel tank! So...Small Line brings fuel "TO/IN" carb thru short brass connect on carb. Other carb connect goes to bulb suction "IN", Then primer bulb "Pressure OUT" goes thru the larger tube "back to fuel tank". Trust me I know how frustrating a simple diagram is to find online fo this set up. And if you have a carb problem on top of the hook up uncertainty you got frustration. Not only was online help hard to find (Mfg...etc NFG at all!) My local repairshop in BBrook NJ could not tell me how!!! and thats no lie! Walbro has a "generic" carb diagram but no "hook up info" specifically. Poulan don't list it either. And these things routinly fall to pcs. all 3 of mine crumpled together on yr. 3 of use.

no should be fairly straight forward! you can find the tubing at ace lowes home depot! good luck & happy trimming!!

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