Snowblower Oil Smells Like Gas? Solved

You have likely just saved yourself a ton of money and heartache. Nice work you! A smell of gas from the engine oil is a cause of concern and needs immediate attention. Engine oil contamination is serious and often ends with a seized engine and that means replacing the motor, Ouch!!.

A leaking snowblower carburetor float valve is the most common cause of a snowblower’s oil smelling like gas. Engine oil contamination is serious and can cause an engine to seize. The repair is simple, replace the float valve and change the engine oil.

In this post you’ll learn how to diagnose why your snowblower’s engine smells of gas. You’ll learn what oil contamination is and why it’s so serious. You’ll also learn how to fix this problem and importantly how to prevent it happening again.

Mower gas cap

Vented Gas Cap

Diagnosing Contaminated Snowblower Oil

A smell of raw gas from the engine oil is a sure sign the carburetor needle valve is leaking gas. However, there are a ton of other symptoms associated with a leaking carburetor float valve, your snow blower may exhibit many or some of these symptoms in addition to the smell of raw gas from the oil.

Common symptoms include:

  • Smell of raw gas in the garage
  • Excessive oil level
  • Leaking gas from carburetor
  • Engine flooded with gas
  • Engine sputters when running
  • Engine hydro-locked
  • Air filter gas soaked
  • Gas tank drains overnight

If you have one or more of these symptoms, then it’s pretty conclusive, the carb float valve has failed.

Mower gas tank

Winged & Threaded caps

What is a carburetor float valve?

The carburetor float and valve work as a team inside the carburetor bowl. Their job is to control gas flow to the bowl. The bowl is a reservoir of gas that stands ready to feed the engine on demand.

The float is made from plastic and floats on the gas level, inside the bowl. The needle valve is attached to the float and as the float rises, the valve seals the fuel feed port.

As the snowblower’s engine consumes gas, the gas bowl level drops and so does the needle, gas once again begins to fill the bowl. This is a continuous process.

The needle valve employs a rubber tip to seal the carburetor fuel feed port, however some carbs use a rubber seat in the port itself. In both cases, the rubber perishes over time and this allows gas to leak into the gas bowl.

(Ethanol gas blends are harder on rubber components than straight gas, as a result it’s advisable to use a gas stabilizer in all types of small engine kit, more on this later)

The leaking valve eventually overflows, which spills into the cylinder through the open inlet valve (usually). This causes the engine to lock, it’s a condition known as Hydro-locking.

When an engine is hydro locked, it won’t crank over and often convinces the operator they have a flat battery or a problem with the pull start assembly.

Given time the gas filled cylinder will leak past the piston and rings and settle in the crankcase with the engine oil.

This is why the engine oil stinks of gas, and the oil level will show very high on the dipstick.

Vented mower gas caps

Vented gas caps

Checking engine oil level

Go ahead and check the oil level, for those that are a little foggy on the process follow these steps:

  • Park snowblower on level ground and the engine is off for at least 5 minutes
  • Locate the dipstick, often marked with an oil symbol or the word “OIL”, in addition the dipstick cap may be a contrasting color
  • Remove dipstick and clean it with a rag
  • Reseat the dipstick (do not screw home threaded type dipsticks to test)Remove the dipstick and read the level
  • Dipsticks employ an upper mark to signify full and a lower mark to signify low, the area between may be hatched, this indicates an acceptable oil level

To sum up, if you have a high oil level and it stinks of gas, go ahead and change out the needle valve.

Replacing Carburetor Float valve

The needle valve is easy to swap out and only costs a few bucks. As said there are two types, a rubber tipped valve or a full metal valve with accompanying rubber seat.

The rubber tipped valve is easier to fit as the rubber seat type can be tedious to remove and fit. In any event we’ll cover both types here in this section.

Tool you'll need:

  • Wrench set
  • Clamp or needle nose grips

First off we’ll need to access the needle valve, to do that we’ll need to remove the gas bowl. When replacing the needle valve, it’s advisable to replace the gas bowl gasket and the bowl fastener too. Older carburetor gaskets often leak after benign disturbed.

To replace the needle valve, follow these simple steps:

  • Turn gas tap off or pinch the fuel line using a clamp – removing the gas bowl will cause fuel to flow continuously unless stopped
  • Remove the gas bowl fastener (usually one)Remove the float pin – slides out
  • Remove the float together with the needle valve (needle valve tips often turn pink when worn)

If your valve has a rubber tip, great! You got it easy. Simply replace the valve in reverse order. If however, your valve doesn’t have a rubber tip, it means you have a little more work, but not much.

Follow these steps to remove and replace the rubber seat type:

  • With the valve and float removed use a small wood screw to extract the seal from the gas feed port. Thread the screw gently into the port and pull firmly
  • To fit the new seal, use a small dab of silicone grease to help it seat. Use a suitable tool such as the chuck end of a correctly sized drill bit to press home the new seal
  • Fit the new valve and needle
  • Have some rags handy, turn the gas on and lift the float, gas flow should stop with the float lifted
  • Clean and refit the gas bowl, be sure not to pinch the bowl gasket or overtighten the bowl fastener. A weep from the bowl after the repair means the fastener gasket or bowl seal are damaged and need to be replaced

In addition to replacing the valve, consider using the gas tap when the snowblower is not in use, this takes the load off the valve.

I advise using a gas stabilizer, this helps protect the rubber and plastic components of the fuel system from the corrosive effects of Ethanol. In addition, gas stabilizer keeps the Ethanol fresh for longer which also protects the carburetor from gumming up over the summer months.

Gas stabilizer should be used in all small engines, 2 and 4 stroke. Check out this post where I explain how and when to use it. Here’s a link to the gas stabilizer I use “ Snowblower maintenance tools”.

We’re not finished just yet, it is really important to change the oil after making this repair. Diluted engine oil will damage the engine. If your snowblower has an oil filter, change it also.

We’ll cover oil changes in the next section.

How To Replace snowblower Engine Oil

Engine oil should be changed on all machines at least once a season and preferably at the start of the season. Although your snowblower may not have done a ton of work since the last oil change, moisture and fuel acids collect naturally inside the engine, this contaminates the engine oil.

Tools you'll need:

Most oil changes are made pretty easy by most snowblower manufacturers. Most engines will employ a drain plug at the base of the engine. Some offer tool-less draining, which is nice.

For the most part you won’t need many tools

  • Adjustable wrench
  • Rags
  • Oil catch container
  • Funnell
  • Oil filter tool (if oil filter fitted)

Follow these steps to nail the oil change procedure like a pro:

  • Park snowblower on level ground – more accurate dip readings
  • Warm engine (if applicable) – warm oil flows faster and more completely
  • Locate and remove dipstick – improves oil drain
  • Use a suitable drain container and have some rags handy
  • Locate and remove oil bung
  • Tilt engine toward the drain bung and allow drain completely

Your engine may have an oil filter fitted. An oil filter is easy to identify, they’re cylindrical and are fitted in an accessible area.

  • Oil filters are threaded to the engine, to remove, use an oil filter tool to turn filter counter clockwise
  • Use rags to clean oil spill
  • Before fitting the new filter, oil the seal using fresh engine oil
  • When tightening the new filter (clockwise) tighten by hand – Do not use tool
  • Go ahead now and refit the oil drain bung
  • Set the snowblower level again
  • Using the funnel add oil

Most engines will run very happily on 5W30 or 10W30, but it’s always best to check with your engine maker.

As snowblower engine sizes vary, oil quantities will also.

It’s important to fill the engine until the dipstick reads full. An extra procedure is required for snowblower engines that employ an oil filter.

Oil filtered engines need to be started and run at idle for a minute until the oil fills the filter. The oil level will require further topping up.

After completing the oil change, run the engine and check for leaks.

That’s it, you nailed it!

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Auto Technician and Writer at Lawnmowerfixed | Website

John Cunningham is an Automotive Technician and writer on Lawnmowerfixed.com. I've been a mechanic for over twenty years, I use my knowledge and experience to write "How to" articles that help fellow gear-heads with all aspects of mechanical repairs, from lawn mowers to classic cars.