Cross section of ryobi 18v trimmer

SOURCE: Gas Trimmer will not stay started

My straight shaft trimmer will idle but dies when the I pull the trigger.

SOURCE: Ryobi Electric string trimmer

TJ, I've had the same problem since yesterday and I found the solution (lots of googling - that's how I found your post BTW).
It turned out that the switch malfunction is a common problem.

The part number for the FA3-4 switch is:

ut41002a-36 ("switch assembly")

Available here (thru Amazon):
http://factorylawnandgarden.com/product/553902/B000PLVCX8/SWITCH_ASSEMBLY_UT41002A_36/

It's a Homelite part, which is identical to Ryobi.

Here is the manual showing it (part 6):
http://www.m-and-d.com/pdfs/ryobi_tool/RY41002.pdf

Here is the thread with the solution:
http://www.ryobitools.com/dc/dcboard.php?az=show_topic&forum=112&topic_id=597&mesg_id=597&page=3

HTH,
Adi

Paul Evans

• 50 Answers
• Posted on Jan 03, 2009

SOURCE: I believe my Ryobi 12 VoltBattery Line trimmer need a new battery

First, check to see if the charger is working properly. To do this, recharge the battery for about 15 minutes. Then check to see if it now runs the trimmer. If so, then you have a bad battery. You can go on the WEB and find a replacement. These batteries or sensitive to heat and cold. When storing, try to place it in a comfortable environment. Sorry for your loss. If it still under warranty, check with the Co.

SOURCE: Ryobi Trimmer

To install string in the Ryobi you do not have to disassemble anything: Line up the two arrows on the inner and outer reel, remove any excess string, cut two pieces of string about 10 feet, feed line in the side holes, secure line in hole where it comes out the bottom (it only takes about 1/4in. to do so), pull strings tight, then turn the inner reel counter clockwise to wind it. If it sticks a little just pull line a little.
To remove the inner spool in order to remove line that has broken inside, to clean the mechanism, or to perform other maintenance, grasp the outer reel and unscrew the bump knob counter-clockwise. Mine is often very tight and requires pliers to get enough leverage. While you are in there, clean the inner reel and the inside of the outer reel to improve feed performance. The shaft rarely needs cleaning. Do not lubricate. After re-installing the reel, add string (0.080") as described above.

SOURCE: Ryobi SS30 Carburetor Problems

Replace thecarb screen, make sure you can see through the screen