I have an MTD lawnmower with a 5 hp “Quantum Power” Briggs & Stratton engine. I can’t get it to run - here’s the troubleshooting I’ve done so far:
Checked oil & gas - oil is full, gas is new.
Pulled spark plug & cleaned.
Replaced spark plug with new one.
Checked air filter - it’s clean.
Checked spark - it sparks.
Bought some starter fluid - when I spray some starter fluid into the air filter, it starts right up and runs great, for about 5 sec.
Looks like it’s not getting fuel, it seems to me. With the air filter off, I can press the primer bulb and intermittently see some gas squirt. Okay, now I squirt starter fluid, pull the rope, and then quickly start pressing the primer bulb. By madly pressing the primer bulb I can keep the mower running, but when I stop the mower dies.
Start at the tank and check every component between that and the carburetor. Check your fuel lines for cracks, check if there is a fuel filter which could be clogged, etc.
Finally, check to see if there is a small engine repair shop near you.
If the mower has been sitting for a while, it is likely that the jets are clogged with a varnish-like substance that is the result of gasoline deterioration. Modern fuel doesn’t store well and stagnates quickly.
Cleaning the carb is the best way. As said above, blow air through the jets to be sure they unclog.
A remotely possible course of remedy is running a very small amount of mineral spirits with the new fuel and the jets MAY clear up.
A product I have used for years is Stabil, a fuel preservative. ( no connection, not a salesman, yada yada yada.
Why the “modern” qualifier? In point of fact, today’s gasoline is a good deal more stable than that from, say, twenty years ago. It still eventually breaks down into a tough varnish, but it takes longer to do so.
I disagree. In my experience the fuel and its additives tend to “varnish” much more quickly than in the past. 40 years experience with small engines ( mostly motorcycles) speaking.
Thanks, Q.E.D. (and others). I couldn’t find the fuel filter, but when I pulled the fuel line off the carb the gas was free-flowing. I would think this means no clog up to the carb. I pulled the bowl off and find the float is a little sticky. I freed it up and put it back together. Now when I reattach the fuel line I have gas pouring out everywhere, including the primer bulb. I’m going to go take it all back apart and look for gasket problems, etc, but if the float valve is bad, the whole carb must be replaced?
Perhaps not. You may be able to get a carburetor rebuild kit which will include gaskets, springs, valves, o-rings and other wearable parts. Check with a local small-engine repair shop; they should either be able to supply such a kit or tell you where to get one for your particular carb.
ETA: Try bending up the tab on the float assembly where it actuates the valve, so that it will close with a slightly lower level. Some carbs have a screw adjustment for this purpose, but most small-engine carbs have a tab you bend to make the adjustment.
Okay, I took it all apart, checked gaskets, sprayed a bunch of WD40 around to try and clean it up some, and carefully put it all back together. It seemed that the float got pinched a bit when the bowl was put back on the first time and may be why the valve seemed to be stuck open. After all the above, things seem different though not yet well. No leak now. The mower will start easily without starter fluid, but will only remain running when the primer bulb is touched repeatedly. It seems as though the float valve is now stuck closed. Also, there is a strange thing with the primer bulb now. It feels like there’s some slight suction on it and if I press it, gas wants to come out the air hole in the center. Before it seemed to fully filled with air and I could hear an air whoosh with each press. Does any of that make sense?
Something that has not been looked at is the throttle. Look for a cable problem. The clamp holding the cable by the carburetor may be lose or the cable may have gotten pinched. No matter how you adjust it at the lever on the handle it may not move the lever on the carburetor.
Thanks, all. I checked the throttle cable, etc - it’s all in pretty good shape and functioning properly. While I thought it had stopped leaking, when I went back outside after a break, I find that all the gas has leaked out of the tank. I’m done with this for this weekend - almost time for Cowboys vs Bears.
I sure appreciate all the help.
