Me so useful

I’ve talked many times about how neighbors have come to my rescue, in ways large and small. Makes me feel good when I can be of a little use myself.

Neighbor D is getting ready to put the last coat of adobe on the outside of his house, in between rainstorms. He’s got a big mud mixer, which hasn’t run in two years. In putting it to bed, he broke Joel’s Rule #1 for Small Engines: Empty the Fuel Tank and Carb First.

So I got a call this afternoon: Engine won’t start. Can I help? I went over, confirmed that the on/off switch was set to ON, confirmed that the on/off switch was plugged in, checked spark. Engine had good spark. Pulled the spark plug: Nothing wrong there.

Opened the fuel cap and took a sniff: Whew! Bad, bad gas.

Filled a syringe with good gas, squirted a little into the carb inlet, pulled the starter. Engine started immediately and then died. We’ve got carb troubles. And I’ll bet I know why. Next question: How serious?

Okay: On small engines there are two kinds of carburetor. Neither likes bad gas, but for different reasons. On diaphragm-type carbs in chainsaws, bad gas is serious trouble. Serious as in this engine will never run again without a carb overhaul. I don’t know why, but bad gas attacks the material the diaphragms are made of, turning them stiff and brittle and unable to do their thing.

On needle-and-seat carbs, which describes the vast majority, bad gas can cause varnishing. Bad gas with water contamination can cause severe corrosion: You’ll pretty much need a new carb. A little varnishing will just gunk up the inlet needle, and is fairly easy to repair. The needle has to be able to move freely up and down in its seat. Since the engine started readily with fuel injected into the carb inlet, I knew there was nothing wrong with spark or compression. The only remaining question was how badly chingered up the carb was.

I dropped the float bowl. Some dirt but no water and no sign of corrosion. Float moved freely and didn’t seem flooded. Of course that didn’t mean the needle worked. On some carbs you can see the needle from the float bowl and confirm that it’s moving, but this wasn’t one of those carbs.

We pulled the fuel line, drained and flushed the tank. Reconnected and refilled. I had a bad feeling the needle was stuck. Several times squirted fuel into the inlet and cranked. Several times the engine started and died. The fuel bowl was surely full by now, but the engine did not want to start. The next step was a carb overhaul. I pretty much gave up but D, more motivated, kept pulling the starter. And then…bingo! We got lucky.

Of course clean gasoline makes a very good solvent. Minor varnishing will sometimes spontaneously dissolve when bathed in fresh gas. It’s not the way to bet, but sometimes you get lucky. Once the needle freed up, the carb started flowing fuel properly. The engine started right up and ran like a champ. D’s back in the adobe business.