How to Troubleshoot Bolens BL110 String Trimmer

Having problems with your Bolens BL 110 trimmer? Not sure how to fix it? Well, here we have discussed all the common problems that arise with trimmers and their solutions.

There can be multiple reasons why your String Trimmer won’t start or doesn’t stay running, this can include a faulty primer bulb, a carburetor that hasn’t been cleaned in a while, a bad clutch, etc.

We will cover all the possible reasons for your problems and some solutions that you may apply.

Another one of the common reasons why your trimmer might be having trouble starting or running properly can be a defective spark plug.

So before you do anything else, first check your spark plug using a spark plug tester. If the testers don’t spark when you turn on the engine, then there is a problem with your spark plug. In such a case, you may have to replace the spark plug or fix the ignition coil.

Bolens BL110 Trimmer WON’T START?

There can be multiple reasons as to why your trimmer isn’t starting!

It can be due to a faulty primer bulb that is pumping that isn’t pumping the correct amount of fuel for the trimmer to start. Another common problem is a clogged carburetor. If the fuel is not able to pass through the carburetor, the trimmer will not be able to start.

We have discussed how you can check the primer bulb, as well as clean the carburetor in the following section.

In case you don’t know how to start a trimmer, here’s a quick guide!

Refer back to this image if you get confused about any terminology!

  1. Move the lever to the “1” position.
  2. Press the primer bulb 10 times.
  3. Squeeze the throttle trigger and keep it that way for the next couple of steps.
  4. Pull the rope 5 times.
  5. Move the throttle to 2.
  6. Make sure your throttle is still squeezed.
  7. Pull the rope again about 5 times to start the engine.
  8. Once the engine starts, release the throttle. Next, wait for about 30-60 seconds and move the lever to “3”.

Once you’ve tried to start the trimmer in the correct way and it still won’t start, then it’s time to diagnose the problem!

1. Check for Compression

Before you put fuel in your trimmer, try to power it by pulling its rope, in order to check the compression, If the engine fights back fine, then there is compression in the trimmer.

You can use a compression tester to check the compression. Any level above 100 psi means your engine can run fine. However, if the compression is less than 100 psi, that means the engine has worn out. In this situation, you should consider replacing the piston ring.

If the compression is fine, then it’s time to move on to the next step of diagnosis.

2. Put fuel in the throat of the carburetor

  • There are 4 screws holding the cover at the back of the trimmer, in place. Unscrew them.
  • Remove the cover. 
  • Use a cloth to clean any oil or dirt.
  • Put a small amount of fuel inside.

Once done, try starting the trimmer again, if it still doesn’t work, keep reading.

3. Check the Fuel Line

Check the tank and make sure that the fuel line is placed properly. The point where the fuel line comes to the tank is where the filter should be sticking up.

4. Check the Primer Bulb

A broken primer bulb is a very common issue for a string trimmer that is not starting.


  1. Remove the tubes coming from the fuel tank to the primer bulb i.e., the fuel lines.
  2. Give the primer bulb a little push from the back and it will come out.


  1. Make sure that the pressing bulb is completely fine, and not broken.
  2. Check that on pressing the bulb, it pushes out fuel from one tube, and on release, it sucks in fuel from the other tube.

If there is a problem with the primer bulb, then replace it. You can easily find primer bulbs in your local hardware store or on amazon.


Place the new primer bulb in position. The two ports on the back of the bulb are of different lengths. The longer port is connected to the tube coming from the fuel tank. The other port is for the tube going to the top of the carburetor.

After replacing the primer bulb, fill the fuel tank and try again, if it still doesn’t works, then it is very likely a carburetor issue.

5. Remove the Carburetor from the Engine

Before you proceed forward, remove the carburetor. Unscrew the two bolts holding the carburetor to the engine. Disconnect any tubes or knobs of the engine connected to the carburetor and take it out.

6. Remove the Pumping side

Remove the tube connected to the primer bulb, from the carburetor. There’s a screw in the center of the pumping side. Unscrew it and remove the side.

7. Check Valve Flaps

Make sure to check the valve flaps on the internal side of the pumping side (that you just removed), they should be flat and parallel with the rest of the diaphragm.

You can check this by looking at it from a side. If any flap is not parallel, then you will have to find a new carburetor to replace this one.

8. Clean the Internal Screen

Make sure that there is no dirt on the internal screen, as it will disturb the smooth flow of fuel to the carburetor. If the internal screen is filled with dirt, that might indicate that there is no filter in the fuel tank.

9. Remove the Metering side

Remove the plate on the metering side and inspect the diaphragm. If the metering diaphragm is very hard and stuck badly, then you will have to replace it with a new one.

10.  Cleaning the Carburetor

Now, unscrew and remove the needle and the rocking arm assembly very carefully.

Next, spray the carburetor cleaner on both the metering side and the pumping side. Make sure that the cleaner passes through the screens on both sides. After that, check that the fuel can pass through the screens.

Connect the Carburetor back to the Engine

Reassemble the carburetor back together. Connect the new metering diaphragm. Connect the pumping side back as well. Once that is done, connect the carburetor back to the engine.

11. Testing the Flow of Fuel

Once everything is in place, add fuel to the tank. Now start pressing the primer bulb. The fuel should flow to the bottom port of the carburetor. Then it should come out of the top port of the carburetor, and go into the shorter port in the back of the primer bulb.

The fuel should then leave the bulb from the longer port, through the tube, and back to the tank.

That’s about it! Now test your trimmer and it should run perfectly fine.


Adjust the carburetor!

If your trimmer starts but dies soon, then the problem is with the tuning of your carburetor. Proper running of the trimmer requires a proper fuel mixture.

To ensure a proper fuel mixture, there are different screws that adjust the flow of fuel in different conditions. These screws perform the task properly if they are tuned perfectly. We have a complete guide on carb adjustment for Bolens BL110 that you can check out.

Another reason why your trimmer might be dying after starting can be old fuel.

Try putting on some new, clean fuel in the tank especially if you have not been using the trimmer for a long time. Make sure you empty the tank first so the new fuel doesn’t get mixed with the old one.


If the engine of your trimmer is working fine, but its head is not spinning or is spinning very slow, then follow the following steps –

1. Check the Throttle Cable

Make sure that the throttle cable is not broken and is connected correctly. Test this by observing the throttle cable and make sure it moves when you squeeze the trigger.

2. Check the Cable in the Shaft

There is a long cable in the shaft, connecting the head to the engine. If your trimmer’s head spins even a little bit when you squeeze the trigger, that means that the cable is completely fine.

In case the head doesn’t rotate at all, disconnect the shaft from both sides, the engine and the head. You will be able to see the ends of the cable from both sides.

Take out the cable and inspect it. If it is broken, buy a new one and replace it. If not, put it back together and connect the ends back to the engine and the hard. Then connect the shaft back as well.

If your cable was fine or if the problem is still there, then move on to the next step.

3. Check the Clutch

There are 3 screws holding the housing of the shaft to the engine. Unscrew them, and remove the shaft. Next, remove the shaft cable from the clutch. Turn on the engine, and observe the clutch.

When the engine is on but you are not giving any throttle, the clutch should remain idle. However, on giving the throttle, the clutch should rotate.

If your clutch does something else, replace it with a new one. This should solve the issue and the head should spin fine after the replacement.

If your old clutch works properly, connect the cable and then the shaft back to the engine and move on to the next step.

4. Check the Gears in the Head

Move to the head of the trimmer. You will see 4 screws on each corner and 1 in the center of the gearbox.

  1. Loosen the 4 screws and remove the center one. This will allow you to disconnect the head and the gearbox from the shaft.
  2. Remove the cable from the gearbox. Look inside the gearbox and you will see the slot made for the cable.
  3. Spin the head and observe that slot. It should spin along with the head.
  4. If it doesn’t spin accordingly, replace it with a new one.
  5. While placing the new one, make sure you align the cable and the cable slot inside the gearbox.

Once everything is back in place, turn on your trimmer. It should now be working perfectly fine!

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