Willie
I have a customer who is disabled an has a 16kw generac NG and during a power outage he call me saying that his generator was making a funny noise. I went right over and heard that the generator was missing on 1 cylinder. I couldn't shut it down right away as he was getting out of the shower and needed his wheel chair shower lift. After about 10 min. When I could shut it down I could hear that from time to time it would run like normal. I shut the unit down and checked the spark plugs. On the back cylinder I found that the spark plug had very little gap and what gap was there had some debri in the gap causing the plug to be fouled. I could also see that there was oil in the front cylinder. I took out both plugs and turned over the engine a few times to rid the cylinders of any oil. I regaped both plugs and reinstalled them. I thought that the oil had come from the crank case breather hose as the one cylinder was not firing. I tried to restart the engine and all I could get was a backfire. My next problem was the OEM starter failed. It had very slow rpm and would crawl to a stop. I ordered a new starter and installed it. It works fine now as it has bigger windings compaired to the OEM starter. Now back to the engine. It won't start, it just back fires. I decided to do a compression check and I have 0 compression. I tried a leak down test. I got the front cylinder to top dead center and hooked it up to my air compressor. The air goes in and a small amout comes out the dip stick tube. Bad rings? Now for the questions. How can a engine be running and when I shut it off now has 0 compression. Could this be from the back firing after the shutdown? Would a fouled plug cause the rings to go bad or do you think the oil in the cylinder screwed them up. Is it worth a rebuild. Should I tear down the heads to inspect them further. Has anyone seen anything like this. Thanks Willie
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bronco
I think that there will be some leakage past the rings all the time, if the rings were bad you would have a lot of air comming out of the dipstick tube. Did you check the valve adjustment? If the valves are ok then my thought is the head gasket is blown causing no compression. Model and serial number could be usefull.
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Scotty306134
Willie something doesnt make sense.. If during the leakdown test it only leaked a little from the breather and I assume nothing from intake or exaust, there has to be some compression when it's turning over. I'm very suspicious of Your compression gage. Did You do a leakdown test on the rear cyl? Since all You're getting now is backfiring is it possible You got the sparkplug wires reversed when You removed the plugs? Hope this helps, Scotty
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Scotty306134
Another thing.. if it's got low hours is it still under warranty?
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ohmslaw
Valve issues will render no compression even if there is no leak. No air in nothing to compress. Vacuum created on the intake stroke. Why a leak down on the front cylinder and not the rear? How did you stop the crank from turning when you applied air pressure? Crank case leakage is normal to a degree. Did you use an actual leak down gauge? Did you observe the rocker arms ? Are they moving properly? Did you check the valve adjustment?
You cam may be suspect here.
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Dave Carney
Was the "break-in" oil ever changed out? Things would wear pretty quickly if it wasn't.
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