Mower won't start

imamoronJuly 9, 2014

I have a Scotts mower with a 16hp Kohler engine. It sat for a year when the starter gear broke. I have replaced the starter, as well as the spark plug, fuel lines and fuel filter. Removed and cleaned gas tank, and have fresh gas. Oil is clean an uncorrupted. It turns over but will not fire, not so much as a cough or a sputter. I have verified spark, and compression seems to be fine. I have pored gas down the carb but no change, have sprayed starter fluid(either) in the carb, no change. If I remove plug and turn over, I do not get any gas thrown out the spark plug hole. It seems the gas is not getting from the carb to the cylinder, and infact I just removed the intake manifold and gas pored out. Am I right that something is preventing fuel from entering the cylinder? And what might the cause be?

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If you can remove the valve cover you can manually turn the flywheel and see if the valves are opening, mainly the intake valve. You may have broken a push rod or something.

You should also list the motor's model number so we know what we are dealing with.

    Bookmark   July 9, 2014 at 7:26AM
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OP - also noticed you did not mention cleaning out/rebuilding carb? Best to remove Take plenty of before after pixs, soak in carb cleaner liquid overnite, probe all orifices with stiff brass small dia wire and magnifier to spot all small passageways - blow all out with compressed air - rebuild carb with new carb kit using fresh gaskets/seats.

old carb may have had dried up fuel inside,which turns to jel blocking new fuel to combustion chamber...

    Bookmark   July 9, 2014 at 11:29AM
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optsyeagle and rcbe, thank you for your interest and responses. I have given some poor information in that I confused the motors on two of my mowers. The problem engine is in fact a Briggs and Stratton model #28N707 type 0162 01, I think it is17 hp. The rest of the post is accurate. I will pull the valve cover off this weekend, although not sure what that will tell me or what further service/repair that will facilitate. Thank you again for trying to help.

    Bookmark   July 10, 2014 at 11:14AM
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Well the only way the gas will accumulate in the intake and not make it to the combustion chamber is if the intake valve is not opening. With the valve cover off, turn the flywheel by hand clockwise and observe the lower valve. Does it get pushed in after two full turns or not. If not investigate why. That is my thought.

If gas is accumulating in the intake manifold the other thought is that it is gas that is leaking past your inlet needle on the carb and flooding the motor, preventing it from starting. I would think that you would see that gas blow out the spark plug hole but perhaps not. To test the flooding, if you can clamp off the fuel line from the gas tank, remove the spark plug and crank it 10 to 15 times to blow out as much liquid fuel as possible. Then put the spark plug back in, open up the fuel line and try to start it as quickly as possible. If you get it to papump, then it was probably flooding. If you get it to start and it runs fine, then just install a manual fuel shut off valve between the fuel tank and fuel filter and use it for storage. If it starts and eventually floods out again, you would need to remove the carb and figure out why the inlet needle is not closing properly. Either a bad float or crud in and around the inlet needle.

Also, give the oil dip stick a sniff to see if you can detect the smell of gas. Usually a leaking inlet needle will allow gas into the crankcase. If you do confirm flooding you should definitely change the oil.

    Bookmark   July 10, 2014 at 12:42PM
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Alrighty then ... Removed the valve cover and the diagnosis was easy, rocker arm broken in half. How difficult will this be to replace?

    Bookmark   July 13, 2014 at 6:22PM
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I finally got around to replacing the rocker arm and unfortunately it appears my problems don't end there. The push rod is not moving when I turn the engine over, it appears to be stuck in an outer most position. Exhaust push rod, rocker arm, and valve are functioning properly. Is it new or rebuild engine time? Or perhaps a whole new/used mower?

    Bookmark   August 2, 2014 at 2:11PM
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I would confirm that in fact that the end of the push rod is seated in the tappet down in the block. and that the tappet itself moves when cranking or not. If it does, do the ends of each of the valves seem even when the piston is 1/4" past TDC after the intake valve closes?

    Bookmark   August 2, 2014 at 7:52PM
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Ok good advice, it appears push rod was not seated properly, after removing and reinserting, I now have rocker arm and valve function. I adjusted the valves as close to specs as I was capable, but of course, my problems are not over. It appears I am still not getting fuel. However at least now, unlike before, the engine will fire when gas or starter fluid is put in through the top of the carb after removing the air cleaner. As soon as the gas is consumed, 2 or 3 seconds, the engine dies and will not start with normal cranking. Will only fire if gas is poured directly in. I have cleaned out fuel tank, replaced all fuel hoses and the filter. I assume my issue is now the carburetor. Not looking forward to removing it and taking it apart but I would think that's my next step. Any thoughts or further advice?

    Bookmark   August 15, 2014 at 1:24PM
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Does this engine have a fuel pump?

    Bookmark   August 15, 2014 at 3:28PM
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No fuel pump

    Bookmark   August 15, 2014 at 3:51PM
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I didn't see notes on the valves- if they appeared to be equally protruding from the cylinder head.Plus verify that the guides that are inside the spring also protrude the same from the head- taking into account the valve seal on the intake. There is a reason that the rocker had broken...

    Bookmark   August 15, 2014 at 3:58PM
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The valves seem to be as they should be, when turning the fly wheel the appear to be cycling and functioning as they should and motor runs fine for a few moments when gas is poured into the air intake

    Bookmark   August 15, 2014 at 5:48PM
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Many auto parts stores have loaner tools. Maybe grab a compression tester to see what you have there. I suppose that it is possible that you lost a throttle plate screw which is holding the valve slightly open or keeping the plate wedged shut. How likely that the plate is shut isn't very much, but at least be sure that the throttle shaft moves.

    Bookmark   August 15, 2014 at 6:49PM
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Thanks tomplum but pretty sure it's a fuel delivery issue

    Bookmark   August 15, 2014 at 7:15PM
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I'm pretty sure that a stuck throttle shaft from sitting for a year would cause a fuel delivery issue. I see several a year that the carb shaft no longer moves after being stored. The natural position of the shaft is typically open. Just make sure it moves freely for now. If you are still nervous about pulling the carb, start off by removing the bowl and seeing what you have inside. Put a catch pan below the carb and see if you have a steady stream of fuel once you unclamp the line. Or maybe you just need to flush the old stale fuel out of the carb. Remember inside the carb is where it is exposed to air and the fuel deteriorates- right where it is needed to be fresh.

    Bookmark   August 16, 2014 at 12:20PM
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