Gas Pressure Washer Maintenance: Oil, Spark Plugs, and Winter Storage

The Mistake That Cost Me $300

I still remember the smell. It was February, fifteen degrees out, and I walked into my shed to grab a shovel. Instead, I found my pressure washer sitting in a puddle of its own fluids. The oil had turned to milky sludge. The pump was seized solid. That brand new Troy-Bilt 3000 PSI unit I bought for $450 was now a $300 paperweight because I was too lazy to drain it before winter.

I learned the hard way so you don't have to. Let me walk you through the three things that keep a gas pressure washer alive: oil changes, spark plugs, and winter storage. Do this stuff right, and that machine will outlast your neighbor's marriage.

Oil Change: The Blood of Your Machine

Most gas pressure washers run a small 4-stroke engine. They burn oil fast, especially under load. I change mine every 50 hours of run time, or once a year if I've barely used it.

Tools you'll need:

• SAE 30 or 10W-30 non-detergent oil (I use Briggs & Stratton 10W-30, $8 at Home Depot)
• Funnel with a flexible spout ($4)
• Oil drain pan (old baking dish works fine)
• 15mm or 17mm socket wrench (check your manual—most use 17mm)
• Rags and nitrile gloves

The exact steps:

Run the engine for 2-3 minutes to warm the oil. Warm oil flows like water. Cold oil is thicker than my dad's oatmeal.

Shut it off and pull the spark plug wire. This is critical. I forgot once and bumped the pull cord. The engine fired and threw my drain pan across the driveway. You don't want to be the guy chasing hot oil.

Locate the drain plug on the engine block. It's a bolt near the bottom. Place your pan under it, then loosen with the socket. Don't strip the threads. I use a slow, steady pull on the wrench.

Let it drain for 10 full minutes. While it drains, clean the area around the fill cap with a rag. You don't want dirt falling into the engine.

Replace the drain plug and tighten it snug. Not gorilla tight. Just snug plus a quarter turn.

Fill with oil. Most engines take about 20 ounces. Pour slowly. Check the dipstick every 5 ounces. Overfilling is worse than underfilling. It causes foaming and loss of power.

I aim for the full mark on the dipstick, never above. Replace the cap. Clean up any drips. Done.

Spark Plug: The $2 Fix for Most No-Starts

Your pressure washer won't start? Nine times out of ten, it's the spark plug. Not the carburetor, not the gas. The spark plug. I've replaced plugs that looked perfectly fine and the engine fired right up.

Tools:

• New spark plug (Champion RJ19LM is standard, $2.50 at AutoZone)
• 10mm socket or spark plug socket
• Feeler gauge (the little metal fan tool, $5 for a set)

Step by step:

Find the plug. It's on the side of the engine, under a thick rubber boot. Pull the boot firmly. Feel that snap? That's normal.

Use the socket to unscrew the plug. Turn counter-clockwise. Go slow. If it's stiff, use a breaker bar. I cracked a ceramic insulator once rushing with a ratchet.

Before you toss the old plug, look at it. A black, sooty tip means the engine runs rich (too much fuel). A white, ashy tip means it's lean (too little fuel). A wet plug with gas smell means the engine is flooded. That's helpful info.

Now the gap. Every plug has a specific gap. The champion RJ19LM needs .030 inches. Use your feeler gauge. Slide the thickest blade that fits between the electrode and the center tip. It should be a snug drag, not loose. Bend the electrode gently with the gauge tool if needed. Don't pry on the center tip or you'll break it.

Put the new plug in by hand first. Turn it until you feel resistance. Then tighten with the socket about half a turn more. Over-tightening cracks the insulator. Under-tightening makes it pop out and damage the piston threads.

Reattach the boot. Press until you hear it seat. Done.

Winter Storage: The Thing That Matters Most

If you skip everything else in this article, don't skip this. Winterizing is what separates a machine that starts in April from a machine that gets thrown in a dumpster.

The full process, in order:

Step 1: Stabilize the gas. Fill the tank to the top with fresh gas and add STA-BIL marine formula (the blue stuff, $10). That's important. Regular STA-BIL works okay, but the marine formula handles ethanol gas better. Ethanol attracts water. Water destroys carburetors.

Run the engine for 5 minutes with stabilized gas. Let it work through the carb. Then shut it off.

Step 2: Drain the carburetor. Most pressure washers have a small brass screw on the bottom of the carb bowl. Put a cup under it and unscrew it a turn or two. Gas will flow out. Let it all drain. This prevents varnish from plugging the jets.

Step 3: Fog the engine. Buy a can of fogging oil ($12 at any parts store). Pull the spark plug, spray a 2-second blast directly into the cylinder, then spin the engine over with the pull cord 3-4 times. This coats the cylinder walls and rings. Prevents rust.

Step 4: Change the oil. I already covered this. But do it now, after the engine has been run. Warm oil comes out easier and carries contaminants with it.

Step 5: Deal with the pump. The pump is the weak link. Inside it, there are tiny ceramic plungers and brass valves. If water freezes in there, the whole pump cracks. Use RV antifreeze (propylene glycol, $4 a gallon—the pink stuff). Not engine antifreeze. The green stuff kills aluminum seals.

Disconnect the water inlet hose from the house. Attach a short 3/8" garden hose to the pump's inlet. Stick the other end into a jug of RV antifreeze. Pull the starter cord slowly until pink fluid comes out the outlet hose. Do this 4-5 times. The pump is now winterized.

Step 6: Store it right. Tilt the pressure washer so the water drains out of the spray gun. I lean mine with the handle against a wall so the gun points down. I also disconnect the high-pressure hose and coil it loosely. Tight coils kink the rubber.

Store it in a dry place. A shed is fine. A garage is better. Never, ever store it outside under a tarp. Tarps trap moisture. I lost a throttle cable to rust using a tarp one winter.

Step 7: Bring the battery inside (if electric start). Those little batteries freeze and die. I take mine out, charge it full, and store it on a wood shelf in my basement. A concrete floor drains the charge.

What About the Spring Start-up?

Come spring, I do the reverse of winterizing. Drain the RV antifreeze from the pump by running clear water through it for 30 seconds. Install a fresh spark plug. Fill with new gas (old gas gets mixed in my lawn mower, not stored for next year). Prime the carb by pulling the cord 3 times with the choke off. Then choke on, pull once. It fires every time.

If it doesn't fire, check the spark plug gap again. That's still the most common problem.

How often should I change the oil?

Every 50 hours of run time. If you only use it twice a year, change it once annually.

Can I use car oil in my pressure washer?

I wouldn't. Most pressure washer engines run SAE 30 non-detergent. Car oil has detergents that hold dirt in suspension. You want that dirt to settle in the oil pan, not circulate.

My pump is leaking oil. Is it dead?

Probably the shaft seal. A $15 seal kit can fix it if you're handy. But if it's a cheap pump, just buy a new one. It's not worth rebuilding a $80 pump that takes 2 hours to fix.

Do I need to run the pressure washer dry before storing?

No. Running it dry damages the pump seals. Use the RV antifreeze method instead.

What if I already froze my pump?

Check for cracks in the pump casing. If you see one, the pump is junk. If no cracks, try running it on a warm day. Sometimes the ice thaws and it works fine. But it's a ticking time bomb. Buy a replacement pump and have it ready.

That's it. Do this stuff one afternoon before the first freeze. You'll save yourself a headache and a good chunk of cash. I promise.