The Tool Desk
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What “clogged” can mean
A grease gun that will not pump is not necessarily clogged in one place. Air trapped in the tube after a refill can interrupt flow; a blocked grease fitting (often called a zerk) or hose path can stop grease reaching the lubrication point; and an obstruction in the gun’s check valve or filter can prevent delivery. These problems can produce similar symptoms, so start with what you can observe rather than taking the gun apart.
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The DEWALT DCGG571 instruction manual lists an empty tube, air pockets, a clogged check valve, a clogged filter, and battery or rod-related issues among possible causes of poor or absent delivery. It also connects grease escaping through the relief valve with a potentially blocked zerk. Those are model-specific troubleshooting clues, not proof that every grease gun is built or serviced the same way.
It helps to think of “pressure” as the gun’s ability to move grease through the hose and coupler to the intended fitting—not as a reason to make the gun work harder. A gun can seem to have lost pressure because air interrupts the grease column, because grease cannot pass a blocked fitting, or because an internal obstruction prevents delivery. The right next step depends on where the flow stops and what the gun is doing. Restoring prime may solve air in the tube, but it will not clear a blocked zerk or automatically clean a filter.
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Make the gun safe before troubleshooting
Stop pumping before inspecting or disconnecting the hose or coupler. If the gun is battery-powered, remove the battery as directed by its manufacturer before handling components that could move or discharge grease. Before disconnecting a coupler or opening any part of the grease path, follow the model’s manual for relieving pressure; do not assume that loosening a fitting is a safe way to release it.
- Never aim the hose or coupler at yourself or another person. High-pressure grease can penetrate skin and cause a serious injury.
- If grease is injected through the skin, seek emergency medical care immediately and tell clinicians it may be a high-pressure injection injury, even if the wound looks small.
- Do not force a stuck trigger, pry at a fitting while the system is pressurized, or remove a purge or relief valve unless the manual instructs you to do so.
- Keep cleaning and internal service steps specific to the gun’s manual. Solvents, tools, and disassembly methods are not established as suitable for every grease-gun design.
Identify the model before following a procedure. A manufacturer’s instructions for one gun may call for a purge valve, while another model may use trigger cycling and a manual priming method. The examples below show why it is important not to combine procedures from different manuals or assume that a valve, timing interval, or rod position is universal.
Use the symptom to choose the next check
| What you observe | Possible cause to investigate | Next action |
|---|---|---|
| No grease after changing or refilling the cartridge | Air pockets or loss of prime; also check that the tube is not empty and that the rod and plunger are engaged as specified. | Use the model’s air-purging or priming instructions. |
| No grease, with no clear connection to a recent refill | Empty tube, battery issue on a powered gun, rod or pressure issue, or an obstruction in the check valve or filter. | Check the basic supply and power conditions, then follow the manual’s troubleshooting sequence. |
| Grease comes out at the relief valve instead of the intended point | On the DEWALT DCGG571, a blocked zerk is one listed possibility. | After following the manual’s pressure-release directions, disconnect the coupler and clean the zerk and grease path as directed. |
| Priming does not restore delivery | The cause may not be trapped air; a blocked fitting or an internal check-valve or filter obstruction may remain. | Move to the relevant model-specific cleaning or service instructions rather than repeating an unrelated priming step indefinitely. |
This is a way to choose a first check, not a substitute for the troubleshooting chart in the manual. A recent refill is evidence that air may be involved, but it does not establish that air is the only problem. Likewise, grease at the relief valve is a clue to inspect the fitting path on the cited DEWALT model; it does not establish that every relief-valve discharge has the same cause.
Check the simple causes first
- Confirm there is grease in the tube. A nearly empty or empty cartridge cannot supply grease. If you have just installed a cartridge, verify it is seated and prepared as the manual specifies; cartridge-loading details vary by gun.
- Check the power source if the gun is powered. Confirm the battery is charged and correctly installed according to the manual. A battery-powered gun that does not run and a gun that runs but does not deliver grease are different symptoms.
- Inspect the rod and plunger position. The rod may need to be engaged or set in a particular way for the cartridge-loading or priming method. Use the manufacturer’s directions for your model rather than guessing at a universal position.
- Look for visible leakage or an unexpected exit point. Note whether grease appears at the hose, coupler, relief valve, or lubrication point. That observation helps locate the interruption, but it does not by itself prove which internal part has failed.
- Record whether the problem began after a refill. A new loss of flow immediately after loading makes trapped air a sensible first check. If the gun had been working and the problem appeared during use, also inspect the fitting path and consult the manual’s other causes.
These checks separate basic supply and setup problems from a possible blockage. If the battery-powered gun does not run, start with the power and model instructions rather than treating the issue as a clogged zerk. If it runs but grease does not emerge where expected, check the tube, prime, and flow path in the order set out by its manual. A rod or plunger that is not engaged as the instructions require can also affect delivery, so avoid changing its position by trial and error.
Purge trapped air using the procedure for your model
Air pockets can interrupt grease delivery after a refill. The DEWALT DCGG571 instruction manual says, “Air pockets in the grease can cause the grease gun to lose prime.” Its purge sequence is an example for that model, not a universal grease-gun procedure.
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DEWALT DCGG571 sequence
- Find the purge-valve procedure in the DCGG571 manual. Unscrew the purge valve only until air escapes; the manual says not to remove it.
- Tighten the purge valve once the air has escaped.
- Uncap the hose as directed and run the gun with the trigger for 10–20 seconds.
- If grease still does not flow, repeat the manual’s sequence.
The details matter: the cited instructions say to loosen the valve until air escapes, not to remove it, and to tighten it before running the gun. The 10–20-second run and repeat instruction belong to the DCGG571 procedure. Do not transfer that timing or valve sequence to a gun whose manual gives different directions. If air does not escape or the sequence does not restore flow, do not keep loosening parts or pumping indefinitely; use the manual’s next troubleshooting step.
If you have a different DEWALT model, do not assume these steps or timing apply. Check that model’s manual, including any instructions for battery removal, hose position, or pressure release.
Milwaukee M12 example: a different approach
The cited Milwaukee M12 Cordless Grease Gun Operator’s Manual uses a different sequence. It directs the user to hold the hose at its spring strain relief and point it away from the body, then cycle the trigger in three-second intervals until grease appears. If repeated attempts do not work, the manual describes manual priming using the rod and bleeder instructions. Follow the exact manual for the specific M12 gun rather than substituting the DEWALT steps or inventing a combined procedure.
The comparison is useful because “prime the gun” does not name one universal repair. The DEWALT DCGG571 procedure uses its purge valve and a 10–20-second run; the cited Milwaukee instructions describe trigger cycling in three-second intervals, followed, if needed, by manual priming with the rod and bleeder. Both are model-specific instructions. Use the exact model and its manual as your guide, rather than choosing whichever sequence seems easier or borrowing one part of each.
If grease exits through the relief valve, inspect the fitting path
Grease appearing at a relief valve is a useful clue, not a verdict that the gun must be replaced. In its DCGG571 troubleshooting table, DEWALT lists a blocked zerk as a possible reason for this symptom and directs users to disconnect the coupler and clean the zerk and grease path.
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- Stop the gun and follow its manual’s pressure-release procedure before disconnecting anything.
- Disconnect the coupler from the fitting as directed by the manual.
- Inspect the zerk and the accessible grease path for blockage. Clean them using only the method the manual specifies.
- Reconnect the coupler correctly and retry according to the gun’s instructions. If grease still exits at the relief valve or does not reach the lubrication point, stop and consult the model’s troubleshooting or service guidance.
Do not treat grease at the relief valve as permission to keep pumping harder. If cleaning the fitting and path does not resolve the symptom, the remaining cause may be elsewhere in the gun or fitting assembly.
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For this symptom, the first question is not “Which new gun should I buy?” but “Is the fitting path blocked, and what does this model’s troubleshooting chart say?” The DCGG571 manual’s direction is to disconnect the coupler and clean the zerk and grease path. That offers a specific check before assuming the gun has failed. If the symptom persists after the documented cleaning and retry, use the manual’s further guidance instead of repeating the same attempt or increasing force.
When to investigate the check valve or filter
Once the tube, power source, rod position, priming procedure, and accessible fitting path have been checked, continued no-flow may point to an internal restriction. The DCGG571 manual separately identifies a clogged check valve and clogged filter as possible causes and provides cleaning instructions for that model.
Use those instructions only if they match your exact gun. Manuals can specify different access points and service methods; the cited instructions do not establish a universal solvent, tool, or disassembly procedure. If the relevant steps are unclear, the parts are damaged, or cleaning does not restore delivery, contact the manufacturer or an authorized service provider rather than improvising internal repairs.
Do not collapse these possible causes into one generic “clog.” The check valve and filter are separate items in the DCGG571 troubleshooting information, and the manual gives separate cleaning guidance for them. A successful air purge does not show that either part is clear. Conversely, evidence of a blocked zerk does not establish that the check valve or filter also needs service. Follow the applicable troubleshooting branch and stop where the manual’s instructions end.
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Verify the repair without forcing the gun
After the manual’s priming or cleaning steps, check whether the gun delivers grease normally through the hose and coupler using the operating method specified for that model. Keep the hose pointed away from people, and stop if grease appears at an unexpected outlet, the coupler will not seat correctly, or the gun continues to resist pumping. A successful prime can restore flow when air was the only issue; it does not establish that a blocked fitting or internal obstruction has been cleared.
If a coupler is visibly damaged or will not connect properly, replacement may be appropriate, but verify compatibility with the gun’s model, thread, and pressure rating. Cleaning is the first response to an ordinary blockage; the available DCGG571 instructions do not establish replacement as a general cure for a clogged grease path.
After troubleshooting, match the result to the original symptom. If the gun had lost prime after a refill, confirm that grease now flows using the operating method in the manual. If grease had been exiting at the relief valve, confirm that the fitting-path cleaning and retry addressed that symptom. If the outcome is unchanged or grease appears somewhere unexpected, stop rather than interpreting partial movement as a complete repair. Do not use a damaged coupler or one whose fit or rating has not been verified for the gun.
Decide whether to keep troubleshooting or seek service
- Continue with the manual if the symptom matches a clearly documented priming or cleaning procedure and the relevant parts are accessible as described.
- Stop and seek model-specific service if the gun remains blocked after the documented steps, the relief valve continues discharging grease, or the manual calls for a service procedure you cannot safely perform.
- Replace a part only after identifying the problem and confirming the correct fit and pressure rating. A no-flow symptom alone does not show that the whole grease gun—or even the coupler—needs replacement.
When you contact service, describe the model, whether the gun is powered, whether the problem began after a refill, what you observed at the hose, coupler, zerk, and relief valve, and which manual steps you tried. Those details help distinguish loss of prime from a fitting-path or internal issue without guessing at a repair. If a step is not covered clearly in your manual, ask the manufacturer or authorized service provider before opening an internal component.
Source manuals for the model examples
The model-specific procedures above come from the DEWALT DCGG571 Instruction Manual, Type 1 N434292 and the Milwaukee Tool M12 Cordless Grease Gun Operator’s Manual. Because a publication date is not established for either cited manual, use the current instructions supplied for your own gun when they differ. The DEWALT DCGG571B product information describes features of that model, including its hose and coupler, air-bleeder valve, and pump filter screen; those details should not be generalized to other grease guns.
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Frequently Asked Questions
Why won’t my grease gun pump grease?
There are several possible causes, including an empty tube, trapped air after a refill, a battery or rod issue on a powered model, a blocked zerk or grease path, or an obstruction in the check valve or filter. Start with the simple supply and power checks, then follow the troubleshooting sequence for your exact model.
How do I get pressure back in a grease gun after refilling it?
If the gun has lost prime, use the air-purging or priming procedure in its own manual. The DEWALT DCGG571 instructions, for example, call for loosening—not removing—the purge valve until air escapes, tightening it, and running the gun for 10–20 seconds; repeat if needed. Other models use different procedures.
Why is grease coming out of the relief valve?
For the DEWALT DCGG571, a blocked zerk is one possible cause listed in the manual. Follow the gun’s pressure-release directions, disconnect the coupler as instructed, and clean the zerk and grease path using the model-specific method. Persistent discharge calls for further troubleshooting or service.
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No. Priming addresses loss of prime from trapped air; it does not necessarily clear a blocked zerk, hose path, check valve, or filter. If the model’s priming steps do not restore flow, move to the relevant troubleshooting and cleaning instructions rather than repeating an unrelated step indefinitely.
Can I use the DEWALT steps on a Milwaukee grease gun, or vice versa?
Do not assume so. The cited DEWALT DCGG571 procedure uses a purge valve and a 10–20-second run. The cited Milwaukee M12 instructions use trigger cycles in three-second intervals and, if needed, manual priming with the rod and bleeder. Consult the manual for the exact model you own.
Do I need to replace the grease gun or coupler if it is clogged?
Not necessarily. A no-flow symptom alone does not show that the whole gun or coupler needs replacement. Clean the fitting and grease path as directed by the manual first. Consider a coupler replacement only if inspection shows it is damaged or will not connect properly, and verify the model, thread, and pressure rating.
What if the gun still will not deliver grease after priming and cleaning?
The remaining cause could be an internal obstruction or another issue specific to the model. Check the manual’s separate guidance for the check valve and filter where applicable. If the instructions are unclear, a part is damaged, or documented steps do not restore flow, stop and contact the manufacturer or authorized service provider.
The Bottom Line
When a grease gun stops delivering grease, use the symptom to choose the next check: confirm the tube, battery, and rod setup; purge air only by the procedure for your model; and inspect a blocked zerk or grease path if grease exits at the relief valve. If flow remains blocked, follow the gun’s own check-valve or filter service instructions—or seek model-specific service. Do not force the gun or assume one model’s repair procedure fits another.
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