What Is the Stihl 031 AV Oil Pump (Oiler Repair)
The Stihl 031 AV oil pump moves bar-and-chain oil from the saw’s tank to the guide bar and chain. If oil stops reaching them, the pump may be at fault, but a blocked outlet, clogged filter, damaged pickup line, or failed drive can cause the same symptom. Identify your saw’s version before ordering parts or starting a repair.
The basic job of a chainsaw oiler has not changed over time: it must deliver oil while the chain moves. What can change is the pump, drive, and oil-line setup fitted to a particular 031 AV. That is why a symptom alone does not confirm a bad pump.
I teach owners to check the whole oil path before taking apart the clutch area. A dirty bar groove can look like a pump failure, while a broken pump drive can leave the chain running without oil. The safest approach is to identify the saw, inspect simple blockages first, and use the correct service information for any deeper work.
What the Stihl 031 AV oil pump does
The oil pump is the part that feeds bar-and-chain oil from the tank to the saw’s lubrication outlet. From there, oil reaches the guide-bar groove and chain. The pump needs a working oil supply and a working drive; a failure or blockage anywhere along that path can stop lubrication.
The chain oil tank is separate from the fuel tank. During operation, the pump moves oil through a line and outlet toward the bar. The bar groove then helps carry oil along the chain as it travels around the bar.
Some 031 AV setups may differ in pump, drive, or adjustment details. Do not assume that a part shown for one saw fits another just because both are labeled “031 AV.” Use the model and serial number, then compare the pump, drive worm, clutch parts, and oil lines with the matching parts diagram.
A drive worm is a small component that transfers motion from the engine or clutch area to the oil pump. If it is worn, broken, or no longer engaged, the chain can move even though the pump is not being driven. That makes the drive worth checking before you order a pump.
Key point: The oil pump is one part of a system. A blocked outlet or failed pickup can produce the same “no oil” sign.
Safety and checks before oil-pump repair
Safe diagnosis starts with a stopped, cool saw. Disconnect the spark-plug lead, drain the chain-oil tank before disassembly, and protect your hands and eyes. The chain has sharp cutters, and clutch parts can carry spring tension, so do not force components apart.
Before checking the pump, remove the bar and chain and clean the bar groove and oil outlet. Inspect the oil-tank filter and pickup line, too. A blockage or damaged line can limit oil flow and imitate a pump failure.
| Check | What to confirm | Why it matters |
|---|---|---|
| Saw identity | Model and serial number | Parts and procedures may vary by production version |
| Bar and chain | Pitch, gauge, and drive-link count match the bar and sprocket | Mismatched parts can cause poor fit and unsafe operation |
| Bar outlet and groove | Clear of packed dirt and sawdust | A blockage can stop oil reaching the chain |
| Tank filter and pickup line | Clean, connected, and not visibly cracked | The pump cannot deliver oil if its supply is restricted |
| Clutch-area drive | Correct part is present and shows no obvious damage | A failed drive can stop the pump even if the pump itself is intact |
Pitch is the chain’s size designation; gauge is the thickness of the drive links that fit into the bar groove. A 3/8-inch pitch is common on 031 AV setups, while .050- and .063-inch gauges may be found. Check the markings on your actual bar and sprocket rather than treating those examples as a fitment rule.
For any work near the clutch, use the service procedure and proper holding and removal tools. Do not guess at thread direction, torque, or engine speed. Next step: If you cannot identify the saw’s version or the correct procedure, pause before removing clutch parts.
How to diagnose an 031 AV oiler problem
A no-oil symptom does not by itself prove the pump has failed. Start with the bar, outlet, tank filter, and pickup line, then inspect the pump drive and pump if the simple checks do not explain the problem. This order helps avoid replacing a sound part while the real fault remains.
Use the saw’s operator’s manual for its oil-delivery test. The goal is to confirm a visible trace of oil from the bar tip while the chain is moving, using the manual’s method and a safe setup. There is no dependable single flow-rate figure for every pump version and adjustment, so avoid judging the system by an assumed volume per minute.
| Observation | Possible cause to investigate | Sensible next check |
|---|---|---|
| No visible oil trace | Empty tank, blocked outlet, clogged filter, failed pickup, drive fault, or pump fault | Recheck the entire oil path, starting at the tank |
| Oil reaches the outlet but not the chain | Dirty bar groove or blocked bar passage | Clean the groove and outlet; inspect the bar |
| Oil delivery changes after cleaning | Dirt or blockage may have restricted flow | Clean the bar and outlet again as part of routine care |
| Chain runs but lubrication remains absent | Pump drive may be disengaged or damaged; pump or lines may also have failed | Stop the saw and inspect using version-specific service information |
Do not run the chain dry to “see what happens.” A moving chain without oil can overheat, wear rapidly, damage the bar, seize, or fail. Stop if you cannot confirm lubrication, then check the supply, drive engagement, pump, and assembly.
Illustrative repair scenarios: If cleaning the bar groove restores a visible oil trace, a pump replacement may not be needed. If the tank filter and line are clear but the drive worm is damaged, replacing only the pump may leave the saw without lubrication. These examples show why diagnosis should cover the full path; they are not proof of a specific fault on your saw.
Stihl 031 AV oil-pump repair sequence
Pump repair involves the clutch-side components on versions where the pump drive is located there. The exact removal order and parts can vary, so use a parts diagram and service procedure that match the saw. This is not a job for improvised tools or guessed fastener values.
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Prepare the saw. Disconnect the spark-plug lead, drain the chain-oil tank, and remove the bar and chain. Clean debris from the outlet and clutch area before opening the saw.
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Confirm the correct procedure. Identify the model and serial number, then check the matching service information. Confirm the required clutch holding and removal tools and the specified thread direction. Do not force the clutch if it will not turn as expected.
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Remove clutch components as specified. Follow the service sequence to remove the clutch and sprocket components. Keep parts in order and note their orientation. Do not guess at torque values during reassembly; use the correct service data.
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Inspect the drive and oil path. Check the pump drive worm and pump drive for wear, damage, or loss of engagement. Inspect the pump, oil lines, tank filter, seals, and outlet for cracks, blockage, or wear. A pump that looks intact may still be unable to deliver oil if the supply line or drive has failed.
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Replace defective parts only with matched parts. Use the parts diagram to confirm the pump, worm, lines, and related components. Do not enlarge oil passages or push wire through a pump. Either action can damage parts or change the oil path.
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Reassemble and test. Follow the matching service procedure, refill with bar-and-chain oil, then refit the bar and chain. Set chain tension as instructed in the operator’s manual. Verify oil delivery by that manual’s test before cutting.
If you lack the correct holding tool or service instructions, have a qualified chainsaw technician handle clutch removal and pump installation. Key point: A careful repair preserves both the oil path and the saw’s correct assembly.
Oil delivery, routine care, and safe operation
A repaired oiler still needs regular checks. Before cutting, inspect the chain, bar, and controls, and confirm that oil reaches the chain using the operator’s manual procedure. After use, let the saw cool, clean the bar groove and outlet, and recheck chain tension as directed by the manual.
Use fresh fuel mixed to the ratio specified in the applicable Stihl 031 AV operator’s manual. Do not assume a 50:1 mix; instructions for older saws may specify a different ratio. Keep fuel and chain oil in their correct tanks.
Clean the sprocket area and air-intake surfaces after use. Store the saw securely with the chain covered and out of children’s reach. Follow the manual’s directions for fuel storage and seasonal lay-up, since stale fuel can impair starting and harm fuel-system parts.
For tree work, follow ANSI Z133 work-practice requirements and applicable OSHA rules. Do not fell trees or make overhead cuts without the training, planning, and protective equipment those tasks require.
Conclusion and frequently asked questions
The 031 AV oil pump supplies bar-and-chain oil, but the pump is only one part of the lubrication system. Check the bar outlet, groove, tank filter, pickup line, and pump drive before deciding the pump needs replacement. Match all parts and repair steps to the saw’s model and serial number, then verify oil delivery before cutting.
What does the Stihl 031 AV oil pump do?
It moves oil from the chain-oil tank to the guide-bar outlet so the bar and moving chain can be lubricated.
Why is my 031 AV chain not getting oil?
Possible causes include a blocked outlet or bar groove, clogged tank filter, damaged pickup line, failed pump drive, or faulty pump. Check the full oil path.
Does no oil at the bar always mean the pump is bad?
No. Dirt or a failed filter, pickup line, or drive can stop oil delivery even when the pump is not the cause.
How do I test the oiler?
Follow the operator’s manual procedure and look for a visible oil trace from the bar tip with the chain moving. Do not run the chain dry as a test.
Which oil-pump parts fit my 031 AV?
Use the model and serial number to find the matching parts diagram. Pump, worm, clutch, and line details can vary by production version.
Is 3/8-inch chain pitch correct for every 031 AV?
No. It is a common setup, but verify your sprocket and bar markings. The chain pitch, gauge, and drive-link count must match the fitted bar and sprocket.
Can I use a 50:1 fuel mix?
Do not assume so. Use the fuel ratio stated in the applicable Stihl 031 AV operator’s manual.
Can I remove the clutch without special tools?
Use the correct holding and removal tools and the version-specific procedure. Do not force the clutch or guess at thread direction.
What should I do if oil delivery is still absent after cleaning?
Stop using the saw. Recheck the tank filter, pickup line, pump-drive engagement, pump condition, and assembly, or have a qualified technician inspect it.
Should I adjust the pump to increase oil flow?
Only if your version has an adjustment and its service information explains how to set it. Do not use a generic setting or guessed flow target.
(This article was written by one of our staff writers, Evan Bradley. Visit our Meet the Team page.)
