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  #1  
Old 04-22-2014, 01:32 PM
MichaelK Male MichaelK is online now
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Default Diagnosing a generator problem

I use my 6kw AC Delco generator to supply power to our 240V well pump. The last time the generator was used in November, it performed nominally, and was shut off normally, and left sitting over the winter in the unheated well shed.

Come April, and the generator is locked up. After the first pull of the starter rope, the engine seizes up and stops turning. I've removed the starter rope assembly so I can get at the main engine shaft. Here's what I've observed.

I removed the spark plug so I could see the piston head. The head looks OK, with little carbon buildup. I ran a wire probe inside the cylinder to feel for broken chips, but I can not find any. The spark plug looks intact with nothing broken off it.

Grabbing the main engine shaft, I can rotate the engine freely either clockwise or counterclockwise until the piston reached TDC, where it locks up. It turns just slightly less than 360 degrees either way, but stops at TDC.

My guess would be that a valve might have rusted open and is preventing the piston from reaching the top of it's travel. My next plan is to remove the valve cover and try to observe whether or not the valves are moving as the engine is turned by hand. Would a tap with a hammer on the top of a valve stem break it free? That would be my next course of action unless anyone else has suggestions otherwise.
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Old 04-22-2014, 03:38 PM
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If the piston wasn't moving at all I would suggest a good soak with WD-40 to loosen it up. It would sound like a ring rusted up without use.

I think your plan is a good one to pull the head to see if the valves are moving. I never think a hammer is a good tool for things like this, but maybe a couple light love taps might be OK.
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Old 04-22-2014, 06:43 PM
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Quote:
Originally Posted by coaltrain View Post
If the piston wasn't moving at all I would suggest a good soak with WD-40 to loosen it up. It would sound like a ring rusted up without use.
Does that suggestion still apply if I bring your attention to this statement specificly.

Grabbing the main engine shaft, I can rotate the engine freely either clockwise or counterclockwise until the piston reached TDC, where it locks up. It turns just slightly less than 360 degrees either way, but stops at TDC.
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Old 04-22-2014, 07:36 PM
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Quote:
Originally Posted by MichaelK View Post
Does that suggestion still apply if I bring your attention to this statement specificly.

Grabbing the main engine shaft, I can rotate the engine freely either clockwise or counterclockwise until the piston reached TDC, where it locks up. It turns just slightly less than 360 degrees either way, but stops at TDC.
Who knows - maybe there is some corrosion on the cylinder wall at the top of the piston travel?

Pulling the head would be the best way to see what is actually going on. But, it wouldn't hurt a thing to soak some WD-40 in the cylinder for 24 hours or so. I would bring the piston up as far as it will go, then spray a good dose of WD40 so it floods the top of the piston. Then try again with turning it over by hand after a good soak.

If that would free it up, and you do manage to get it started after that, I wouldn't run it for more than a few seconds then change the oil right away. The WD-40 is a solvent and you don't want any of that in the oil in the crankcase.
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Old 04-22-2014, 10:03 PM
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You should be able to pull a cover to see if the valves and/or camshaft are moving when you turn the crank.

Also what sort of muffler? Mice have been known to take up residence in motors given access.
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Old 04-22-2014, 11:16 PM
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Could be just a chunk of carbon. I'd pull the head and take a look..

Or maybe a mouse made a nest in the generator part and there's an acorn or something in there..
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Old 04-23-2014, 09:20 PM
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If it is an over the head valve engine. It could very likely be a stuck valve. I would take the valve cover off the head positions the piston at BDC or close to it. Take a rubber hammer and tap on the rocker arm. You should be able to see a deflection if the valves are free. They'll open and snap back to the original position. Sometimes just tapping on the valve will break it free and you will be good to go. Just pull the engine threw a few cycles to assure proper operation of the valve train.

Now if you do have a valve that is stuck you can try and work it loose by taking a short length of rope inserting it into the spark plug hole and then turning the engine bringing the piston up to smash the rope and pushing the valve shut. And using some penetrating oil on the valve stem you should be able to free up the valve doing this.

If its not the valve then most likely there is something in the cylinder stopping the piston from going over TDC. Which means the head will need to be removed and the object removed.

But before going through all of this I would disconnect the engine from the generator and make sure the generator is free and not causing the problem.

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Old 04-27-2014, 02:36 AM
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Quote:
Originally Posted by coaltrain View Post
If the piston wasn't moving at all I would suggest a good soak with WD-40 to loosen it up. It would sound like a ring rusted up without use.
Kaplah! That worked! I started with the easiest procedure, which was spraying some WD-40 into the cylinder. After spinning the piston back and forth a few times, the ring must have slid over the rusted portion and was turning again.

I then get the plug back in, attached the starter rope again and started pulling. It didn't try to start till about the 8th pull, then it caught on, and starting chugging out blue smoke. After about 15 seconds, the spray oil got burnt out, and the RPM stabilized and the engine was running normally.

I flipped the AC on and hooked up a power tool to put a load on the generator. I left the load on for about 5 minutes, then I shut it down and started draining the used motor oil.

Thanks for all the suggestions!
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Old 04-27-2014, 03:07 AM
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Glad you got it runnin.

i had very simular issues with my generators, i learned that this crap ethanol gas causes the valves to stick, i had to pull the heads to knock the valves loose. i use a fuel additive now.
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Old 04-27-2014, 10:21 AM
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Awesome! Glad it turned out to be something simple.
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Old 04-27-2014, 11:55 AM
MichaelK Male MichaelK is online now
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I know the drill about long-term motor storage. Run the engine till the carburetor is empty. Unscrew the spark-plug, add a squirt of oil, and crank to distribute.

My generator however is positioned in the back corner, with the plug directly against the back wall, so that got neglected. Don't worry, it will be fine. This is what happens when you do it the easy way instead of the right way.
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Old 04-27-2014, 04:32 PM
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Glad to hear you got it running.
You might want to try adding a little Marvel Mystery Oil to the fuel to add more lube to the cylinders for those long periods when it's not used.
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Old 07-16-2014, 11:11 AM
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One more thing with the ethenol "crap". I did just as you guys did with ethenol and I even ran the ethenol out till it quit.

I found out the hard way on my Honda EZ3500 that the float bowl retains the ethenol and that in a few months leaves a white residue. My small engine guy who is A1 recommended:

1. DON'T EVER USE ETHENOL IN SMALL ENGINES.

2. Use non ethenol only and a additive. He had some Briggs and Stratton which allows fuel to be stored three years.



3. With engine running shut it down and then cut off the gas supply. He said they now recommend leaving good fuel in so the fuel pump/carb gaskets stay "wet".

4. Pull plug and squirt in motor oil and rotate engine over so it will coat wall and get under valve seats.

5. Best results was crank engine and let it run at least ten minutes every 30 days. That is my game plan now and so far so good.

Just last weekend fell into some good info. Met a guy who is a engineer at nuke facility and they have lots of batteries and he says the battery manufacturers recommend a trickle charge on all batteries. He says on his generator at home he can get about 8 years on a 12 volt battery using a small trickle charger. He just replaced one he had been using for 10 years before it died.
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