Do Lawnmower Engines Have Fuel Filters?

Factual Questions
1
      • I have a Sears walk-behind mower that will only run for a while if you put carb/fuel injector cleaner into the tank. It will no longer run on regular “uncut” gasoline. Do these types of engines have any sort of fuel filter? Or is there just something clogging the fuel system inside the carb? I can see that there is a little screen strainer inside the gas tank, there is no debris in the gas tank–I know, because I have to siphon all the fuel out, pour in carb cleaner and then pour in gasoline after that. It’s maybe 4 years old, it was bought new and did not have this problem until this year. I get the oil changed every year, and I think the shop usually changes the spark plug as well… ?
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  • I am finding all these articles online about tearing a small engine all the way down to pistons and valves, but I can’t find anything that says where the fuel filter would be. The main possibility is that there is a large can with a bolt-head in the middle, hanging off the underside of the carb. If that’s not it, then the whole damn engine would need to be taken apart to get at it, nothing else is accessible. <:/
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2

Yes. The fuel filter is often integrated into the fuel tank, IME, and may or may not be a separately replaceable unit. Usually, it’s simply a mesh that’s designed to trap large dirt and debris particles. Backflushing is the usual method of cleaning.

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      • I tried taking off the can and it was just a float bowl. I cannot imagine it being anything other than crap in the fuel delivery stopping things up. Ah well.
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4

Lawnmower questions in November? This is when we expect snow thrower problems. Your timing’s a bit off, but what the heck, either one uses a roughly 4-5 HP engine…

In the four years you’ve had it, have you been putting something like Sta-Bil in the gas tank and running it for a while to ensure it’s mixed in with the gas and gotten through the carb? If not, “varnish” may be your culprit - the “jets” and internal passages of the carb get clogged.

The large “can” under the carb is part of the carb and is called the float bowl. It provides a steady supply of gas to the carb - there’s a float in there controlling a valve. Remove that nut, and the bowl comes off, and the contents of the gas tank will soon be on the floor as the float will no longer be floating, and the valve will open.

If you’ve been having a shop tend to the air filter, oil and spark plug changes, why not just tell them about how you need to feed the mower carb cleaner all the time and have them fix it? At best, you’ll just need to have the gas tank and carb flushed out and cleaned, maybe a carb “rebuild” where the seals and tiny bits (and carbs have a fair number of tiny bits!) are replaced, on up to worst-case, where you need a new carb.

5

The gas is four year old!?

All kidding aside, I suspect that either the gas is too old or has water in it. Drain all of the gas from the tank and float bowl, then try running the lawnmower on fresh gas. If that doesn’t work, then my guess would be that the carburetor is clogged and needs a rebuild.

…And yes, the screen at the fuel petcock in the tank is about all most lawnmowers have for a fuel filter.

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      • Because the local shops around here get about $65 for doing a general tune-up–oil change, spark plug, blade sharpening and air filter. I don’t know what it would cost to get them to do actual work (that takes longer than 20 minutes). So if it is just a simple clog in the fuel supply, I’d be more interested in taking a half-hour of my own time and doing it myself.
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7

Since we don’t have any idea of your mechanical skill level, go to a bookstore, and look for something along the lines of small engine service/repair. Select one that isn’t below your knowledge, and points you in the direction of the goals sought. Another source is the Audel line of texts, which you can purchase online, IIRC.

8

Maybe he’s using the lawnmower to “vaccuum up” the falling leaves?

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Have you tried removing the carburator and replacing the gasket? On some engines the gasket doubles as a diaphram . It controls the suction filling the float bowl.Its a simple repair and its cheap. I would worry using carb cleaner on a plastic carburator.
Also if the carb is plastic it could be warped. I had one warp this spring.
lotsa luck

10

When I got out of High School I worked in a lawnmower repair shop. When I serviced a mower, I would always clean the carb if it needed it also, as part of the tune-up. The only thing extra I would charge was for the rebuild kit if it needed one. The carbs on these things are so simple that you shouldn’t have any problem with them. Remove the fuel line from the carb, cap it off with anything handy. (This is also a good time to remove and flush the fuel tank.) Carefully remove the linkages from the carb., paying special attention to how they are placed. Remove the carb. from the mower, usually 2 bolts. Check behind the carb. for carbon deposits in the intake area, if they are there, just scrape them off. Now remove the float bowl from the carb. Check the needle and seat to assure they are moving freely. If not replace them. Now go crazy with a can of gum-out, being sure to clean every little nook and cranny and every little oriface that looks like fuel needs to go through. Reaasemble the same way you took it apart, just in reverse order…Then, fire it up…

11
      • Re: lawnmower engines in November… it was up around 70 degrees F yesterday. A bit warm for this time of year but not much.
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  • I may try taking the tank off today (even though it’s raining). The gas tank is plastic but the rest of the engine is metal. When I took off the float bowl, it was full of fuel/cleaner.
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