Downstream injectors only pull soap when the low-pressure soap nozzle is open. Twist the lance to the soap side (or put on the soap tip) and wait up to 10 seconds for soap to reach the tip. On a Hi-Lo lance, soap and rinse are switched at the injector lever instead.

Center is rinse only on our lever injectors. Push the lever all the way to one side until it stops. On the 4-soap system, left is Soap Box 1 and right is Soap Box 2.

Pull the soap hose off the injector. Turn the injector to check valve 1, put the lance on soap and pull the trigger. Put your finger over the barb and feel for suction. Repeat on check valve 2. Suction on both: the injector is working, so the problem is in the soap line, soap box or container (keep going down this list). No suction on one side: that check valve is stuck. No suction on either side: check the foam head and nozzle sizes next.

A sealed jug or drum pulls a vacuum and stops the draw, so loosen the cap or open the vent. To prime a soap line, hold the trigger down on soap and pump the draw tube up and down in the container until soap fills the line.

A clogged foam head is the most common cause of no soap or bad foam. Foam nozzle: remove the quick connect and clean out the nozzle (blow it out with an air hose if you have one). Strainer: push out the pin on the foam head, rinse the mesh screen, then put it back together.

The nozzle inside the injector and the tips on your lance have to be sized to your machine's PSI and GPM. Too small and it chokes your pressure. Too large and it will not create suction. Your soap tip should be 3 to 4 sizes larger than your rinse tip (rinse 4004, high-pressure soap 4007), and low-pressure soaping uses a 1540 tip. The last digits of a tip are its size: a 4004 is a 40° spray with an 04 orifice. Look up the right sizes on the Parts tab of the Soap System Calculator.

Water must flow in the direction of the arrow on the injector body: arrow pointing toward the gun, away from the pump.

Push the clear hose fully onto the barb. Check for cracks, kinks or a loose fitting. Any air leak breaks the suction.

Pull the pickup hose out of the container and clear the strainer and the colored metering tip. Rinse them in warm water.

Dried soap can glue the small ball and spring shut. Soak the injector in warm water (or a vinegar and water mix) and flush it. If it still sticks, replace the check valve barb.

Keep the soap container close to the injector, within about 3 to 4 feet of lift. Long pressure hose runs after the injector also reduce draw.

If nothing above fixes it, the injector nozzle or diffuser may be blocked inside. The internal injector nozzle and diffuser are sized to your pressure washer, and every system ships with one internal kit. Keeping a spare kit on hand saves downtime, so call us with your PSI and GPM to order one. Suttner shows how to take the ST-164 apart and replace the nozzles in these videos: Nozzle replacement, ST-164 and Changing the injector and diffuser nozzle, ST-164. Not comfortable doing it? Call us first.

Check your pre-mix or metering tip against the Soap System Calculator. Use a pre-mix or a metering tip, never both. A tip on a pre-mixed drum makes the soap far too weak.

Step up one tip size, or follow the tip the calculator recommends for your GPM.

Remove the quick connect and clean the foam nozzle. Push out the pin on the foam head and rinse the mesh screen. Replace the screen if it is torn or packed with soap.

Test the check valves (see No soap is coming out). Weak suction gives wet, runny foam with no pattern.

Tighten every barb and fitting on the soap side. A small air leak shows up as sputtering, uneven foam.

Do not apply soaps hotter than 120°F. Hot water thins the chemical and makes draw inconsistent.

Some unloaders cycle on and off as the flow changes and make foam weak or sputtering. If your foam pulses, call us with your machine model.

Very thick concentrates draw poorly. Pre-dilute in the drum per the calculator.

Nine times out of ten this is how the wash was done, not the system or the soap. Apply soap from the bottom up so you can see where you have been and nothing gets missed.

Keep the tip 6 to 12 inches from the surface and rinse every inch in a tight, overlapping pattern. On a touchless wash, always rinse from the bottom up so the area you are rinsing still has soap working on it. (Brush washing is rinsed top down, since the brush already did the work.) A loose pattern shows up as dirty stripes.

On a 2-step wash, Step 2 has to cover every spot Step 1 touched to neutralize it. Missed spots can streak or whiten polished aluminum.

Cool hot aluminum with a cold rinse first. In the sun, do one half of the truck at a time (Step 1, Step 2, rinse) so soap never dries.

A 2-step touchless wash is a maintenance wash. Past about 5 days, brush the grilles, glass, mirrors, chrome and stacks.

Your system was set up so the soap dilutes correctly. Changing tips, metering tips or other parts can make the mix too strong and streak polished aluminum. Call us before changing anything.

Twist to the rinse nozzle. It takes about 10 seconds for the soap left in the line to clear.

If soap keeps drawing with the lever centered, the valve inside is not seating. Flush it with clean water while working the lever back and forth. If it continues, the internal seals need a rebuild or the injector needs replacing. Call us.

Turn the knob on the soap box toward the soap you want. Make sure the injector lever is pointed at that box.

The new soap takes 5 to 10 seconds to push through the lines. Keep spraying until it arrives. On a 2-step wash, always finish with Step 2 so it neutralizes Step 1.

Trace the line for that soap from the drum to the box. Clear the strainer and metering tip and push the hose fully onto its barb.

This happens when two soaps are drawn from the same side of the injector and a check valve is not sealing. Test and clean the check valves (see No soap is coming out), and replace the check valve if it keeps happening.

Make sure the pickup tube reaches the bottom of the drum, just off the floor, so it does not pull in sediment.

Flush the injector with clean water and work the lever back and forth. Do this after every use with acid or high pH soaps.

If the lever still sticks or leaks, the internal O-rings and seat need replacing. Call us for a rebuild kit or replacement.

The foam head is clogged most of the time. Clean the foam nozzle and the mesh screen (see No soap is coming out), then test the check valves for suction.

The Foaminator makes foam with a venturi vacuum, so any pressure leak kills it. Lifting the lance puts strain on a worn quick connect or threaded fitting and it starts leaking pressure. Replace the quick connect O-rings or the fitting.

The foam head nozzle is likely too small for your machine. The extra back pressure escapes out the rinse nozzle. Call us with your PSI and GPM to get the right size.

Replace the O-ring in the coupler. Make sure the collar snaps fully forward over the plug.

Wrap threads with thread sealant tape and tighten snug. Do not over-tighten brass. It cracks.

Water from the body itself usually means worn seals, a cracked housing or freeze damage. Rebuild or replace.

Running water hotter than 140°F can destroy the O-rings and seals in the system. Keep it at 135°F or less, and remember soap should go on at 120°F or less.

The valve seat and seals are worn. Our ST-2315 is acid resistant. Replace the gun or rebuild it with the matching repair kit.

Replace the O-rings in the changeover. If the collar is hard to turn, flush it and work it back and forth.

An undersized injector nozzle restricts flow and drops your rinse pressure. Match it to your PSI and GPM on the calculator Parts tab.

Rinse nozzles wear out and open up over time. Replace it with the size the calculator lists for your machine.

With the machine running and the trigger pulled, turn the unloader adjusting nut clockwise until the pressure stops climbing. Never go past your machine's maximum pressure. Then run the lock nut down against the adjusting nut to hold it.

Test the machine with the gun connected directly, no injector. If pressure is still low, the issue is the pump, unloader or water supply.