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Tinkering with an old generator showed me how to spot bad diesel fast
I picked up a beat-up diesel generator from a yard sale to fix in my free time. It kept sputtering out after running for a bit, and I was sure the injectors were clogged. Instead of pulling them right away, I tried a simple trick my dad once mentioned. I drained a small sample of fuel into a clear jar and let it sit for a minute. If you see a layer of water or specks at the bottom, the diesel is contaminated. This quick check saved me hours of work because the fuel was just dirty, not the parts. Now I always test the fuel first on any diesel engine that acts up. What's your go-to method for checking fuel quality without a full kit?
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jason_wells7mo ago
Paper towel test works in a pinch. Dab a little fuel on a white paper towel and let it dry. Good diesel leaves a light stain, but bad fuel with water or crap in it will leave separate rings or dark gunk spots. It's not perfect science but it shows contamination fast.
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wren_butler747mo ago
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averyshah7mo ago
That paper towel test Jason mentioned is so handy! My buddy Mike had his truck acting up last winter, sputtering on cold starts. He dabbed some fuel on a napkin like you said, and when it dried there were these clear separate rings and a dark sticky patch in the center. He figured out his jerry can had a cracked seal and let in condensation. After he swapped out the bad fuel, his engine sounded totally normal again.
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xena8316mo ago
That paper towel trick is a lifesaver when you're stuck without a clear jar. Honestly, just keeping a few of those little glass sample jars from the auto parts store in the toolbox makes it easy. You can see water and sediment way clearer than on a napkin.
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