Why won't my McColluch weed eater create a vacuum

Try cleaning the gas cap. It has a vent and if clogged will slowly create a vacuum. Check the air cleaner too.
If not it may be time to clean the carb, YouTube has videos on most carbs.
I have the same problem with my lawn mower and weed eater.
Hope that helps,
David

This is a tell tale sign of a lean fuel mixture. By choking the unit you are manually creating a richer fuel mixture. I would purchase a compression tester from a local parts store and check compression. If that's ok, I'm willing to bet the problem is still carb related. Two stroke carbs are tricky to clean because of high/low ports that are one way and sometimes impossible to clean. Did you remove high and low needles when cleaning carb? Another trick is to mix seafoam with your gas, then mix two cycle oil to proper ratio. Use 2 ounces seafoam to one gallon of gas, then mix two cycle oil to proper mix. Hope this helps! Good luck and happy wrenching!

I’m happy to assist further over the phone at https://www.6ya.com/expert/layne_0fccff498c319c32

A bad duckbill vent (the little green thing) inside the fuel cap will cause a vacuum to be created if it is NOT venting to the atmosphere. Odd that all new ones you have used are bad. Maybe try using your old, original fuel cap and the carburetor needs adjusting or at the least; a gaket and diaphragm kit installed. Carb screws are NOT user friendly, thanks to EPA and CARB emissions regulations. You can get onto the heads of them to turn them by tapping a 22 gauge automotive-type plastic wire connector onto the head, and that will give you enough grip to turn them. I would TRY adjusting the carb before getting a kit, but after 2 years or so, a G & D kit is usually needed due to the internals of the carb drying out. If you adjust the carb, this is how the manufacturer says to:

http://www.zamacarb.com/tipspage.html

sounds like a carb problem for sure the diaphragm in the carb has hole in it or the jets are clogged forcing it pull fuel at half choke and not fully open also make sure your gas lines are clear and free of trash but i would put a kit in the carb for sure.hope this helps.

You will need to clean the carb or if this unit has a walbro carb buy a rebuild kit and it will work just fine.. Good Luck...

hey harry the float inside the carb is stuck i would suggest rebuilding the carb

If it runs with the choke closed then it's not getting enough gas. Check the gas filter on the end of the gas line in the gas tank. Remove the gas cap and using a piece of wire with a hook on the end, reach in the tank and pull the gas line out through the opening. Check the filter on the end of it. You could also have a burst-ed diaphragm in the carburetor. This sucks the gas from the tank to the carb. If that's the case a new weed eater may be in order unless you can find someone with the parts to repair it. Also check the gas lines for leaks or breaks, 2 of them.

remove the sediment bowl on the bottom of the carb,but dont lose the gasket and watch out when the float drops so the needle and spring in the bore dont fall and you lose them,then clean out any dirt in the bowl and in the needle seat andget some carb cleaner and throughly clean out all openings in the carb,its a california carb thats why there are no adjustments

The short one goes to the primer bulb and the long one, with the filter, goes to the carb.

Jim

It sounds like the carburetor needs cleaned. Take the carb. apart and clean it with carb. cleaner. Use a Den Tech Brush, (used for cleaning teeth), they are perfect for cleaning the small ports in carb. If that still doesn't work, you may need to buy a carb. kit for your weed eater. If so, replace the gaskets and valve needle, and also make sure to replace the small screen. this should all come in the new carb. kit.