String Trimmer Line Won’t Feed? Bump Feed Head Fixes
A string trimmer bump feed head advances fresh line when you tap it on the ground, and when it will not feed, the usual causes are line welded together from heat, an empty or wrongly wound spool, a jammed or worn head, or the wrong line size. Rewinding correctly fixes most cases. Line fused together by heat is the most common jam, so rewinding with the right line, not overpacked, prevents it.
The bump feed head on a string trimmer is meant to let out fresh line with a tap on the ground, so when a string trimmer bump feed will not feed, it is a common and fixable frustration. The head holds a spool of line that a spring loaded mechanism advances each time you bump it. When it will not feed, the line has usually welded together from heat, the spool is empty or wound wrong, or the head is jammed or worn. This guide explains how bump feed works and how to fix it.
How Bump Feed Works
Tapping the head lets out fresh line.
A bump feed head holds a spool of trimmer line. When you tap the head on the ground while it spins, a spring loaded mechanism briefly releases the spool so centrifugal force pulls out a bit more line, then it locks again. So each bump advances fresh line to replace what wears down. When the mechanism, the spool, or the line is not right, that feeding stops working.
Line Welded or Wound Wrong
The most common cause is line fused or wound badly.
Empty Spool or Wrong Line
An empty spool or the wrong line size stops feeding.
| Cause | Fix |
|---|---|
| Empty spool | No line left to feed; refill with fresh line |
| Wrong line diameter | Too thick or thin for the head jams or slips; use the specified size |
| Old, brittle line | Line that sat gets brittle and snaps; use fresh line |
| Line too short in head | Pull some out by hand to start the feed |
Head Mechanism Problems
A jammed or worn head stops the bump feed working.
The Takeaway
To recap: a bump feed head that will not advance line usually has line welded from heat, an empty or wrongly wound spool, the wrong or old line, or a jammed or worn head. Rewind fresh line neatly in the right direction, use the specified size, and clean the head and check the spring.
Because welded or badly wound line causes most bump feed jams, rewinding correctly with fresh line fixes the majority.
If a gas trimmer will not start or run right beyond the head, we can sort it at your Tampa home. Our diagnosis guide tackles trimmer running faults, and the maintenance guide our broader handheld and mower upkeep.
Frequently Asked Questions
Why won't my string trimmer feed line?
Usually the line has welded together from heat, the spool is empty or wound the wrong way, the line is the wrong size or old and brittle, or the head is jammed with debris or has a weak bump spring. Rewinding fresh line neatly in the arrow direction fixes most cases.
How does a bump feed trimmer head work?
It holds a spool of line, and when you tap the head on the ground while it spins, a spring loaded mechanism briefly releases the spool so centrifugal force pulls out more line, then it locks again. Each bump advances fresh line to replace what has worn down.
Why does my trimmer line keep welding together?
Heat from hard use fuses the line coils together so they will not pay out, the most common bump feed jam. Rewind with fresh line, wound neatly and not overpacked, and avoid running the line too short, which heats it. Some users lightly separate coils when winding.
How do I fix a bump feed head that won't advance?
Open the head and check for welded, empty, or wrongly wound line and rewind fresh line neatly in the arrow direction, using the specified line size. Clean grass and debris from the head, and check the bump spring and knob, replacing a weak spring or worn knob.
What size line does my string trimmer take?
Use the line diameter your trimmer specifies, since too thick or thin a line jams the head or feeds poorly. Check your manual or the head for the size. Using the correct diameter fresh line, wound correctly, is key to the bump feed advancing line reliably.
