When your pressure washer stops as you pull the trigger, the reason depends significantly on whether it's an electric or a gas-powered model. For electric pressure washers, this can be a normal function of their auto-start/stop system, designed to save energy. However, for gas pressure washers, it's typically a clear indicator of a mechanical problem, specifically related to the pump's bypass system.
Understanding Pressure Washer Auto-Stop Mechanisms
Both electric and gas pressure washers are designed to manage water pressure efficiently, but they do so differently when the trigger is released or engaged.
Electric Pressure Washers: Normal Operation
Many electric pressure washers are equipped with an auto-start/stop feature. This system detects when you release the spray gun trigger and temporarily shuts off the motor to prevent wear and save electricity. When you pull the trigger again, the motor should instantly restart, and water flow should resume.
- Key points for electric models:
- This intermittent stopping and starting is normal behavior.
- If your electric pressure washer stops when you pull the trigger and doesn't restart, then there might be an electrical issue (e.g., faulty switch, power supply problem, motor overload from an internal fault) that requires troubleshooting beyond the normal auto-stop function.
Gas Pressure Washers: A Sign of Trouble
If your gas pressure washer stops or stalls the moment you pull the trigger, this is generally not normal and points to a problem within the unit's pressure regulation system.
The Core Issue: Bypass System Failure
For a gas-powered pressure washer, the most common reason for it to stop when the trigger is pulled is that the pump is not going into bypass mode, and the resulting pressure build-up overloads the engine, causing it to shut down.
Here's a breakdown:
- Bypass Mode (Unloader Valve): When you release the trigger on a gas pressure washer, a component called the unloader valve kicks in, directing the water flow in a "bypass loop" back to the pump's inlet. This keeps the water circulating at low pressure within the pump without putting a strain on the engine or continuously discharging water.
- What Happens When Bypass Fails: If the unloader valve fails to engage bypass mode correctly when the trigger is pulled (or if it's stuck in the "high-pressure" position), the pump immediately tries to send all the water out through the nozzle at maximum pressure. With no place for the water to go instantly or with a sudden, uncontrolled spike in pressure, the engine experiences an immense and sudden load. This sudden, excessive pressure build-up is too much for the engine to handle, causing it to stall or shut down abruptly.
Common Causes for Bypass Failure in Gas Models
Several components can contribute to the pump failing to enter or manage bypass mode effectively:
- Unloader Valve Malfunction: This is the most frequent culprit. The unloader valve can get stuck due to debris, mineral deposits, or wear. If it's stuck in the high-pressure position, the pump cannot relieve pressure when the trigger is pulled, leading to engine overload.
- Solution: Inspect the unloader valve for signs of damage or blockage. It may need cleaning, adjustment, or replacement. Refer to your pressure washer's manual for specific instructions.
- Clogged Nozzle or Lance: A severely clogged spray nozzle or a blockage in the wand/lance can create extreme backpressure instantly when the trigger is pulled. This mimics the effect of a failed bypass, as the pump struggles to push water through the obstruction, leading to engine strain and shutdown.
- Solution: Always check and clear your nozzle for any debris. Many pressure washers come with a small nozzle cleaning tool. Ensure your spray wand and hose are clear of kinks or obstructions.
- Pump Problems: Internal pump issues, such as worn seals, pistons, or check valves, can impact the pump's ability to regulate pressure correctly or efficiently enter bypass mode. This can lead to erratic pressure behavior and potential engine stalling.
- Solution: A pump inspection by a qualified technician may be necessary. Depending on the severity, the pump might need a rebuild or replacement.
- Insufficient Water Supply: While less likely to cause an immediate stall when pulling the trigger (it usually causes loss of pressure or pump damage), an inadequate water supply can make the pump work harder, potentially contributing to an already struggling engine stalling under the sudden load.
- Solution: Ensure your garden hose is fully open, kink-free, and supplying sufficient water pressure and flow to the pressure washer.
Troubleshooting Steps for Gas Pressure Washers
If your gas pressure washer stops when you pull the trigger, follow these steps:
- Check the Nozzle: Disconnect the nozzle from the spray wand and try running the pressure washer briefly without it (just with the wand). If it runs without stopping, the nozzle is likely clogged. Clean or replace it.
- Inspect the Unloader Valve: Consult your owner's manual for the location of the unloader valve. Check for any visible signs of damage, leaks, or if it appears to be stuck. Sometimes, gently tapping it or trying to adjust its spring tension (if adjustable) can free it.
- Ensure Adequate Water Flow: Verify that your water source is fully open and providing an unrestricted flow to the pressure washer's inlet.
- Examine Hoses and Connections: Look for any kinks, damage, or loose connections in your high-pressure hose or garden hose that could restrict water flow or cause air leaks.
- Professional Inspection: If the above steps don't resolve the issue, it's advisable to have a qualified small engine mechanic or pressure washer repair specialist inspect the unloader valve and the pump for internal damage.
Quick Troubleshooting Guide
| Pressure Washer Type | Symptom: Stops When Trigger Pulled | Common Cause(s) | Solution(s) |
|---|---|---|---|
| Electric | Stops, then restarts | Normal auto-start/stop feature | No action needed; this is expected behavior |
| Electric | Stops and doesn't restart | Faulty motor switch, power supply issue, internal motor/pump fault | Check power source/breaker, test motor/switch, consult technician |
| Gas | Stops and stays stopped | Pump not entering bypass mode, excessive pressure build-up overloading the engine | Inspect/clean/adjust unloader valve, clear clogged nozzle, check pump for damage |
By identifying your pressure washer type and understanding these mechanisms, you can effectively diagnose why your unit stops when you pull the trigger and implement the appropriate solution.
