auto store fuel line is what you have in a car, not correct (or even possible to use) for a trimmer. Replacement hoses are on the order of 1/8th inch and very flexible. Any hardware store should be able to help, Depot and Lowes will have Ryobi branded line kits with both lines, fuel filter/pick up, and wire tool to fish the line through.
1st make sure you have fuel in the tank and that there is a fuel pickup/filter on the line in the tank so the pickup is below the level of the fuel.
Next prime to get fuel into the primer bulb and past into the carb. No fuel in the bulb means broken line right there. Make sure the primer bulb is not cracked also.
Assuming fuel in primer and a couple primes beyond that apply full choke and pull until it "pops" or tries to start then put it to half choke and pull until it starts.
If still no start yes you can use either, but carb cleaner works just as well and is not a one purpose chemical. either/carb cleaner will tell you if you have spark.
I'm a power equipment tech - I recite the above to customers daily.
Lines do crack with age as do primer bulbs. Make sure the run switch is on. you don't want to know how many no start complaints are from that... or leaving the machine outside and the run switch corroding.
After you have spark it must be fuel. lines are the first place to look, but you don't have to replace them to look.. pull the air filter and housing off and look at the lines - touch and move them - cracks, tears, breaks will be very obvious. If the lines are good it's the carb.
Ethenol in the gas today plays hell with carbs - lots of water in the gas leads to lots of corrosion. Good news it plenty of new carbs available ob eBay and it will let you save the machine, bad news is it's not really cost effective to put $60-90 into a $100-$150 trimmer.
We refuse to service Ryobi because of that.
