Troubleshooting Guide: Suttner ST-164 Dual Foam Injector

The Suttner ST-164 is a dual-line downstream injector designed to switch between two chemicals (like Chem-X Stars and Stripes) using a simple red/blue lever. When set up correctly, it delivers consistent, high-quality foam with minimal downtime. However, if you're experiencing issues—such as no foam, a weak draw, or soap not switching—this guide will help you get back on track quickly.

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Common Symptoms & Solutions

1. Soap Isn’t Drawing at All

Possible Causes:

• Injector not activated (too much backpressure)
• Clogged or missing metering nozzle
• Collapsed or cracked pickup tube
• Worn or incorrect nozzle on spray wand
• Selector lever stuck between red and blue

Solutions:

• Use a low-pressure soap tip or foaming nozzle to activate the draw (≥4.0 orifice recommended)
• Check for clogs or damage in the pickup lines and metering nozzles
• Make sure you're not using a high-pressure rinse tip when expecting soap draw
• Ensure the lever is fully clicked to either the red (Stripes) or blue (Stars) side—not in between

2. Weak Foam or Inconsistent Draw

Possible Causes:

• Metering nozzle too restrictive (draw rate too low)
• Soap is under-diluted or too viscous
• Air leak in pickup line
• Hot water reducing chemical viscosity too much

Solutions:

• Swap in a larger metering nozzle (e.g., from green 100:1 to blue 70:1 or beige 30:1)
• Pre-dilute the soap slightly in the jug if it's too thick
• Check all hose barb and pickup tube connections for tightness
• Avoid water temps above 130–140°F to keep draw rate stable

3. ST-164 Lever Not Switching Properly

Possible Causes:

• Internal valve mechanism is clogged or corroded
• Lever is partially stuck between red and blue
• Worn internal O-ring or seat

Solutions:

• Flush the valve with clean water and gently work the lever back and forth
• Disassemble and inspect the valve if sticking persists
• Replace internal seals if needed (available in rebuild kits)

4. Soap Keeps Drawing Even When Lever Is Centered

Possible Causes:

• Internal valve not seating properly
• Residual vacuum still pulling chemical
• Cracked internal seal or seat

Solutions:

• Disassemble and inspect the selector valve
• Clean all internal ports and reseat the valve ball
• If damaged, replace the internal valve kit or injector assembly

5. Water Leaking from the Body of the ST-164

Possible Causes:

• Loose fittings or cracked housing
• Worn internal O-rings or gasket
• Freeze damage

Solutions:

• Inspect and tighten all threaded fittings (QC plugs, barbs)
• If leaking from the body, consider a rebuild kit or full replacement
• Always drain the ST-164 in winter to prevent cracking

Quick Maintenance Tips

• Flush with clean water after every use (especially when using high-alkaline or acidic soaps)
• Remove and clean metering nozzles regularly
• Keep pickup tubes off the bottom of the soap jug to avoid sucking debris
• Store indoors when not in use to avoid corrosion or freeze damage
• Replace pickup tube strainers if clogged or missing

Chem-X Recommended Metering Nozzles

These are starting points—adjust based on foam thickness, water flow, and system PSI.

Still Not Working?

If none of the above steps fix the issue:

• Double-check that your pressure washer is operating within the injector’s range (1,000–4,000 PSI and 1.8–18 GPM)
• Confirm your soap tip or foamer is actually allowing downstream draw
• Consider testing the ST-164 independently by bypassing your lance or gun