the automatic oiler doesn't seem to be working. manual oiler button works, but it doesn't oil on its own when running.

Diagnosis

The failure of the automatic oiling system on the Ryobi RY405110, while the manual primer button still functions, indicates a failure in the automatic pumping cycle rather than a total loss of oil pressure. In this specific brushless model, the automatic oiler is driven by a mechanical gear linked to the motor's drive sprocket. If the manual button works, it confirms the oil reservoir is not empty and the oil is capable of reaching the bar; however, the automatic mechanism is failing to displace oil during the rotation of the chain. This is most commonly caused by a "dry plug" or a buildup of solidified bar-and-chain oil and sawdust (sap-glued debris) specifically within the automatic delivery port. Because the manual primer uses a separate high-pressure burst to force oil through, it can often bypass a partial clog that the lower-pressure automatic pump cannot overcome. Additionally, if the saw was stored for a long period, the internal pump seal may have adhered to the cylinder wall, preventing the automatic gear from cycling the pump. You can confirm this by running the saw for 60 seconds and checking the bar; if the chain is dry but the manual button leaves a visible oil streak, the automatic delivery path is obstructed.

How to Fix It

To restore automatic lubrication, follow these precise steps to clear the delivery system and reset the pump mechanism:

1. Power down the unit and remove the 40V battery pack completely to ensure safety during maintenance.
2. Remove the bar and chain by loosening the side tensioning nut and sliding the bar off the drive sprocket.
3. Locate the oil discharge port on the saw body—this is the small circular hole where oil enters the bar groove. Use a thin 0.5mm steel wire or a sewing pin to gently probe the hole. Do not force the wire deep into the pump, but clear any hardened resin or sawdust "plugs" from the immediate opening.
4. With the bar removed, insert the battery and engage the trigger at full throttle for 10 seconds. Observe the oil port; you should see a rhythmic "pulsing" of oil droplets. If it is dry, press the manual oiler button 5-10 times rapidly to force air and oil through the lines, then try the throttle again.
5. Clean the oil inlet groove on the guide bar itself. Use a bottle brush or compressed air to ensure the channel that leads from the saw body to the chain is completely clear of debris.
6. Reinstall the bar and chain, ensuring the bar is seated flush against the chassis. Tighten the tensioning nut firmly to ensure a tight seal between the oil port and the bar groove.
7. Perform a "splatter test": Start the saw and point the tip of the bar at a piece of clean cardboard or a light-colored concrete surface. Run the saw at full speed for 30 seconds. A consistent line of oil droplets should be thrown onto the surface.

If That Didn't Work

• Check for Air Locks: If the oil reservoir was allowed to run completely dry, an air bubble may be trapped in the automatic pump. Fill the reservoir to the brim with high-quality bar oil and hold the saw at a 45-degree angle while repeatedly pressing the manual primer button to "burp" the system and force air out of the pump housing.
• Inspect the Oil Filter: Some RY405110 units accumulate fine sawdust inside the oil tank that clogs the internal pickup screen. Carefully pour out the remaining oil and use a flashlight to check for a layer of sludge at the bottom. If found, flush the tank with a small amount of mineral spirits or a penetrating lubricant to dissolve the blockage.
• Verify Drive Sprocket Engagement: Ensure the drive sprocket is spinning freely. If the sprocket is seized or the internal gear that drives the oil pump has sheared, the automatic pump will not rotate. If the chain doesn't spin when the trigger is pulled, the issue is mechanical drive failure, not an oiling clog.
• Replace the Guide Bar: If the bar is old, the oil grooves may be packed with oxidized oil and wood fibers that cannot be cleaned. Try a brand new 18-inch Ryobi compatible bar to see if the automatic flow resumes.

Heads Up

• Avoid using "tacky" or ultra-heavy winter oils in high-temperature environments, as these can thicken and cause the automatic pump to stall.
• Always clean the oil port and the bar groove every 5-10 tanks of oil to prevent the buildup of "sap-glue" that leads to this specific failure.
• Never run the saw without oil in the reservoir; running the automatic pump dry can cause permanent damage to the internal seals, rendering the automatic function useless.
• Ensure the bar is tightened correctly; a loose bar can create a gap at the oil port, allowing oil to leak onto the chassis rather than flowing into the bar groove.