How-To
Trimmer Line Won’t Feed? What the BLACK+DECKER, RYOBI, CRAFTSMAN and Toro Manuals Say to Check
Line not advancing, spool jammed, trimmer running slow? The fixes the trimmer makers themselves list in their manuals — auto-feed and bump-feed heads, brand by brand, with page references.
Published
When line stops feeding, the makers’ own troubleshooting sections are more reliable than any rule of thumb. Here is what four operator’s manuals say, grouped by head type. Every manual starts the same way: remove the battery first.
Auto-feed heads (BLACK+DECKER, CRAFTSMAN, RYOBI)
These heads feed line on their own. Don’t bump them on the ground — RYOBI warns this damages the trimmer and voids the warranty, and CRAFTSMAN says not to bump the unit to feed line.
BLACK+DECKER (LST400/LST420 manual) — “Automatic line feed does not work”
- Remove the battery and the spool cap.
- Pull the line until about 5-3/8” (136 mm) sticks out of the spool. If there isn’t enough line left, fit a new spool.
- Check that the line isn’t criss-crossed on the spool. If it is, unwind it and wind it back on neatly.
- Check that the start of the line is pulled tight against the spool.
- Refit the cap (tabs to the cut-outs, push until it snaps) and trim any line that reaches past the trimming blade.
If it still won’t feed or the spool is jammed: clean the spool and housing, check that the lever in the spool housing moves freely, and rewind the line neatly.
If the trimmer runs slowly: check that the spool housing turns freely, and that no more than about 5-3/8” (136 mm) of line sticks out — cut it back to the trimming blade if it does.
CRAFTSMAN (CMCST900 manual) — clearing jams and tangled line
CRAFTSMAN notes that thick or stalky weeds can clog the line-feeding hub with sap, which jams the line. To clear it: remove the battery, press the release tabs and take off the cap, pull out the spool and clear broken line and debris, then refit the spool with the line through the hole in the housing. Press the spool down gently and turn it until it drops into place — once seated it turns a few degrees left and right freely — and keep the line from getting trapped under the spool.
RYOBI (RY402013 manual) — “Line will not advance”
| Cause RYOBI lists | RYOBI’s fix |
|---|---|
| Line is welded to itself | Lubricate with silicone spray |
| Not enough line on the spool | Install more line (a new spool) |
| Line is worn too short | Pull the line while pressing the button |
| Line is tangled on the spool | Remove and replace the spool |
RYOBI also says grass wrapping around the housing and string head comes from cutting tall grass at ground level — cut tall grass from the top down.
Bump-feed heads (Toro 51831 / 51831T)
- To feed line, run the trimmer at full throttle and tap the bump button on the ground; don’t hold it on the ground.
- If the line is worn too short to feed by tapping, remove the battery, then push the bump button at the base of the spool retainer while pulling the line.
- Excessive vibration or noise can mean debris on the drum area (clean it) or a badly wound spool (advance the line, or rewind the spool).
Still not feeding?
A worn or wrong spool is the usual end of the road. Find the spool your model takes in the spool finder, and see the step-by-step guides for the BLACK+DECKER AF-100, RYOBI AC80RL3, CRAFTSMAN CMZST065 and Toro 88616.
Sources: BLACK+DECKER LST400/LST420 instruction manual, “Troubleshooting” (PDF); CRAFTSMAN CMCST900 instruction manual (NA473221), “Clearing Jams and Tangled Line”, p. 8 (PDF); RYOBI RY402013 operator’s manual, “Troubleshooting” and p. 9 (PDF); Toro 51831/51831T operator’s manual (Form 3440-153 Rev D), pp. 14 and 18 (PDF). Checked September 25, 2026.
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