Oil Pump Does Not Work On Chainsaw

Oil Pump Does Not Work On Chainsaw

This article will discuss the repair of the oil pump of a chainsaw. Many owners have encountered such a phenomenon as the lack of oil supply to lubricate the chain or its leakage in the wrong place. Let us analyze the causes of these phenomena and methods of elimination.

How is the oil pump arranged?

The oil feed pump is located on the crankcase, on the same side as the drive. right behind the drive sprocket. To understand how it works, you need to look at the images and see what parts it consists of and what moves where.

So, this is what the oil pump looks like (it may look different for different models, but there is one principle).

And here is his working scheme.

It all works like that.

From the drive through the worm gear rotation is transmitted to the plunger, which, rotating, makes a longitudinal reciprocating motion. This back and forth movement is ensured by the shape of the plunger, an adjusting screw with an eccentric and a thrust spring. When the plunger moves back, the oil is sucked into the oil chamber through the inlet due to the created vacuum (similar to a syringe). When moving forward, oil is pushed through the outlet of the oil chamber. To ensure tightness, a rubber cuff is used (it is not shown in the diagram).

To prevent both holes from being opened at the same time, there is a segment cutout at the end of the plunger. When moving back, it is turned to the inlet, while the outlet is closed. When moving forward, the inlet closes and the outlet opens, since the segment cut-out rotates toward the outlet. Thus, in one revolution, the plunger makes one reciprocating motion.

To reduce or increase the stroke of the plunger, an adjusting screw with an eccentric is used. The eccentric in this case is a cylinder built into the body of the adjusting screw. In this case, the central axis of this cylinder does not coincide with the axis of rotation of the screw, therefore, if the screw is rotated, then the cylinder either approaches the end of the plunger, then moves away from it. Actually this is the essence of the eccentric. Because of this displacement relative to the center, it is often called a cam.

At maximum approximation, the plunger will not have a stroke, and the oil will not swing. At maximum distance, on the contrary, the plunger will have a maximum stroke, which means that it will pump oil to the maximum.

But how does the plunger go back and forth? Everything is simple. Its end face is processed in such a way that in the middle it has a central protrusion, which abuts against the eccentric, and the end edge is made in the form of a ring around this central protrusion. At the same time, the ring is not perpendicular to the longitudinal axis of the plunger, but is at a certain angle, forming a bevel. one part turns out to stick out a little. The adjusting screw and the end face of the plunger are aligned so that the edge of the end face during rotation is in contact with the screw, either the protruding part or the non-unlocking part. When touching protruding. the plunger moves forward. When non-engaging. back. In this case, the plunger moves back due to the thrust spring.

Faults, causes and remedies

What are the malfunctions, we already noted at the beginning. either the oil is not supplied, or leaks where it is not necessary. How to fix it?

No oil

The lack of oil supply, if at the same time it does not leak anywhere, is due to the lack of stroke on the plunger. This may be due to improper installation of the adjusting screw, or due to wear of the plunger itself.

The adjusting screw may not stand properly if you or someone else previously disassembled the oil pump and assembled it incorrectly. In this case, the / marks are correct, but the screw is set to the opposite position. In this case, disassemble the pump and set the screw correctly. Or simply turn the screw closer to “-“. The screw itself, as a rule, does not spontaneously stand in a position blocking the plunger stroke.

The wear of the plunger consists in the fact that the edge of its end has been sharpened so that it does not have a protruding part, but instead the entire edge is in the same plane. In this case, if you do not want to buy spare parts, you can grind the edge of the end face of the plunger, giving it its original shape. in this case, you must not forget and undermine the central protrusion. After such turning, the volume of the oil chamber will increase slightly, as the plunger will move back a little. But it will be pumping nonetheless.

If the pump does not pump, but at the same time oil flows from the chainsaw body, then most likely one of the hoses has been disconnected. either inlet or outlet. If the input, then the oil will flow and not wound saw. If the day off, then it will pour only on an established chainsaw. It’s clear that to fix this problem you just need to put the hoses back on.

Oil is leaking

We examined one of the causes of smudges a little higher, although it is not connected with a malfunction of the oil pump itself. But it happens that a chainsaw works, and even oil is supplied, but at the same time, oil also flows from the case.

This happens if the oil flows through the rubber seal. It may wear out, or was previously incorrectly installed by someone.

Also, along with cuff wear, wear on the walls of the oil pump cylinder itself can occur. In this case, it will be necessary to change the entire pump as a whole, since it is unlikely that it will be possible to find just the pump body without all the other parts.

Video: Oil Pump Does Not Work On Chainsaw


These are the malfunctions of the chainsaw oil pump and how to eliminate them. I hope the article helped you sort this out.

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Cylinder in the lower part it has two holes (only one of them is visible in photo 1 item 4): it is sucked in through one oil, and pushed out into the second.

Plunger (photo 2). this is a steel rod, on the one hand it has a milling groove. flats, and on the second. a plastic or steel gear. When the plunger rotates, the flats alternately open and close the inlet and outlet openings of the cylinder. When translating upward, the flat first opens the inlet (while closing the outlet) and creates a slight decrease in pressure. Due to this, a portion of the oil is sucked into the cylinder. Then, turning, the plunger moves down, opening the outlet hole with the flat (while closing the inlet) and pushing the oil out of the cylinder. So it is fed to the bus in small portions. Due to the high frequency of cycles, a constant and continuous flow of lubricant is created.

Are used two types of oil pumps (photo 3): with an adjustable oil flow rate and an unregulated flow rate. In the first case, the gears of the plunger have an oblique tooth, and the translational upward movement is provided by an additionally installed spring. Oil flow control is carried out by changing the stroke length of the plunger in the cylinder. An example is an oil pump for Chinese saws with an engine displacement of 45-52 cc

In the case of an unregulated oil pump, the plunger has an oblique closed groove in which the fixed stop of the body abuts. The rotation causes the groove to slide along the stop, and since it is oblique, this movement causes the plunger to go forward backward. With such a scheme, it is impossible to limit the stroke of the plunger and oil is supplied in constant quantities. Example. Husqvarna 137, 142 chainsaw oil pump

The torque from the engine to the plunger is transmitted through a special drive unit, which also has a gear. the counterpart of the gear on the plunger. In fact, this is a worm pair. The oil pump drive is driven either by the drive chain sprocket (photo 4 pos. 1), or by the crankshaft itself (photo 4 pos. 2).

In the first case, the plunger is mechanically connected to the drive sprocket and rotates only with it. The photo 4 pos. 1 shows the Stihl MS-180 chainsaw drive. The steel antennae clings to a special recess on the cup of the drive sprocket. When the sprocket rotates, the drive rotates with it. In this case, there is no oil supply at idle.

In the second case, the drive is rigidly fixed on the shaft and constantly rotates with it. Photo 4 pos. 2 shows the drive of the Husqvarna chainsaw oil pump 137, 142. It is pressed onto the shank of the crankshaft and rotates with it constantly. Therefore, oil is constantly supplied, even if the saw is in idle mode.

Usually, one of the gears (either on the plunger or on the drive) is made plastic in order to secure the part with a more complex structure or complicated installation. The first part will break and wear out the plastic part.

On some saws, the oil pump with the drive may be additionally closed with a special cover (photo 5, the cover of the oil pump of the Chinese chainsaw 45-52 cc), which protects the worm joint and the pump itself from dirt and wood dust. On some saws, such as Husqvarna 137, 142, the oil pump housing itself closes the connection between the drive and the plunger, thereby acting as a protective cover.

For normal operation of the tire and chain, a certain amount of lubricant is required. In order for the design of the lubrication system existing on a chainsaw to give out, the oil must have a suitable viscosity. Judging by the mechanics, the oil pump does not care what kind of oil you use: automobile, transmission or special. The main thing is that the viscosity lies in the established acceptable range. However, this does not mean that any oil can be poured. The task of chain oil is not to save you money on its purchase, but to lubricate the parts of the tire and chain. Different oils do this differently. But more about that in another article “Chain oil. What to pour? ".

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Elimination of defects oil pump: chainsaw repair

With prolonged use of the chainsaw, its individual components will fail. In most cases, repair is needed. chainsaw oil pump. This is justified by the fact that during sawing there is a huge selection of chips that can fall into the working mechanism.

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Oil leak elimination

Many saw models during their operation appear malfunctioning oil pump. The nature of these defects is possibly different, but ultimately this leads to an oil leak. In addition, such leaks certainly appear even when the saw is in a supine position. This is justified by the uneven distribution of water in the storage tank.

Leaks also occur due to the fact that the oil pumps for the chainsaw have a hose fitting on their own body. Violation of the density of the connection of the water tank and pump leads to the appearance of oily drops.

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To solve such difficulties, of course, by disassembling the saw and repairing the oil pump. The disassembly process should be approached very carefully so as not to destroy the moving parts of the pump. The following tools are also useful for this purpose:

In most cases, our client is left with oil pumps for chainsaws consisting of 5 main halves. In one half is the working mechanism, and in the next. the storage camera.

If pump leaks, you need to change the gasket between the 2 parts of the mechanism.

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During repair, the unit should be disassembled in half, without touching the working part. There should be a gasket at their junction. In this case, if it has huge transferred sections, then the gasket needs to be replaced.

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If the gasket is not bad, then it should be wiped and installed at the destination. Later the hose is checked. He will not have cracks and diaper rash that will violate his density. If similar defects are found, the hose must be replaced. On the contrary, the hose is not bad, then it needs to be washed, degreased and put on a sealant.

Then they check what remains to make our client output channels where there are no third-party inclusions (garbage, slag, etc.). This debris will lead to congestion, which will create vacuum plugs. For which the design of their detection is intended, the channels should be cleaned. To do this, there is the option of compressed air.

Preventative measures

In order to reduce the possibility of the appearance of various oil leaks in the process of using the saw, it should be periodically serviced. In due time of this process it is necessary to monitor the density of all hoses and gaskets. If they are detected, broach the connecting parts.

It is imperative to inspect the quality of the oil being poured. It will be of high quality and applied in strict accordance with the features that are indicated in the product passport. Under all this, under no circumstances should mining be used, since it has a heterogeneous structure. It is also necessary to do a repeated purge of the oil pump. This will help prevent coking of debris in its working channels.

The low quality of lubricating water will aggravate the quality of the tool and reduce its life.

Today, with poorly produced grease, a chain can fail, a change in which will be required will be a fairly expensive procedure.

After completing the sawing work, it is necessary to permanently clean the saw from sawdust that has fallen on its surface. For long interruptions in work, the chainsaw should be hung upright. This will allow oily water to spill moderately across all channels of the instrument. Such its uniform distribution allows avoiding vacuum plugs that cause malfunction of the oil pump.