Thanks in advance for any assistance! I'm running a 2006 Gravely 272Z, 26 hp Kawasaki liquid cooled engine with a little over 900 hours. It's been a great mower....until the past month. First problem was sudden backfiring and missing. I discovered one of the plugs was VERY loose, I replaced both plugs and all was well, until it wasn't. The next time I mowed for about thirty minutes and the mower shut completely down like it was out of fuel. I tested the fuel shut off solenoid and it was bad. I replaced that and it started right up. Since then it starts right up, seems to run fine for 30-45 minutes then starts losing power under load. Just seems like it can't maintain the rpm's. Doesn't die out completely but is turning so slowly I have to back out of grass. It usually will do this for a few minutes then seems to run fine for awhile, then the problem returns. Over the past few mowings problem seems to be more frequent than at first. Thus far I have cleaned air filters, replaced fuel filter, added fuel stabilizer, replaced fuel pump, cleaned then later replaced carburetor, all to no avail. I don't see any thing wrong with fuel lines but haven't replaced any. Since replacing carb, it does on occasion backfire when throttling down. The problem occurs while running on either of the two fuel tanks. Mower is not burning or losing any oil and the oil color looks fine. If it were rings wouldn't i see smoke or oil loss? Any chance it could be in any way related to drive or blade belt? I'm out running out of ideas. All help welcomed!
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Gravely losing power under load
- Thread starter hospcfo
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Export threadHey friend! I own a small engine shop but I wouldnt call myself a professional lol. Fuel solenoid usually either sticks all the way shut or all the way open. When in deep grass, stop and see if blades speed up. That would be a slipping deck belt. If it has loss in moving forward too, you could check both belts but I'd check cylinders. Compression test will tell you a little but a leakdown test will tell you exactly where compression loss is. Position piston on tdc (easier with valve covers off and spark plugs removed). Turn flywheel manually until intake valve closes then stick a clean screwdriver or rod into spark plug hole and slowly turn. When piston stops that's tdc. Rocker arms will have slight wiggle. While feeding air into spark plug hole, listen for hissing out of dipstick tube which would indicate worn or damaged rings. It's normal to have a little air but not too much. Also make sure engine is warmed up good as the metal will have expanded. Listen for hissing out of exhaust and carb which would be sticking, burnt, or damaged valves. Also listen near head gasket area. Hope this helps!
Oh and see if your carb has an adjustment knob. Some do some dont. Also make sure there isnt debris in gas tank limiting the amount of fuel being pulled through. Make sure there is no vacuum leak on engine side of carb.
Have you checked to see if it is running on both cylinders? Pull one plug wire off and see if it will start. If it starts check the other cylinder. If it only starts on one cylinder, the other cylinder is not getting spark or fuel.
I know you replaced it but have you checked the fuel solenoid again. Maybe a faulty solenoid. I'm no expert of course but also have you tried a compression test?
Thanks. i haven't rechecked the solenoid but I can. I would think if it was bad and stuck closed it wouldn't run at all though. I'm going to pick up a pressure gauge and check that next.
Hey friend! I own a small engine shop but I wouldnt call myself a professional lol. Fuel solenoid usually either sticks all the way shut or all the way open. When in deep grass, stop and see if blades speed up. That would be a slipping deck belt. If it has loss in moving forward too, you could check both belts but I'd check cylinders. Compression test will tell you a little but a leakdown test will tell you exactly where compression loss is. Position piston on tdc (easier with valve covers off and spark plugs removed). Turn flywheel manually until intake valve closes then stick a clean screwdriver or rod into spark plug hole and slowly turn. When piston stops that's tdc. Rocker arms will have slight wiggle. While feeding air into spark plug hole, listen for hissing out of dipstick tube which would indicate worn or damaged rings. It's normal to have a little air but not too much. Also make sure engine is warmed up good as the metal will have expanded. Listen for hissing out of exhaust and carb which would be sticking, burnt, or damaged valves. Also listen near head gasket area. Hope this helps!
Thanks alot for this info. I'll check this out. It usually runs 30-45 minutes okay and then will sporadically lose power, doesn't die out just can't get through the grass. After it does this awhile I can hear the rpm's return to normal and it will cut fine for awhile longer and lose power again. I wasn't sure if either of the belts were slipping if it would cause these symptoms? As for the rings/compression loss possibility I would have thought I would see smoke or be losing oil some and it's not doing either. Do you see some with compression loss without smoke/oil loss?? Lastly, if it were rings any idea what a ball park estimate of fix might be?? I know it can vary, just trying to decide how much to invest in 13 yr old mower. Thanks for you help!
Have you checked to see if it is running on both cylinders? Pull one plug wire off and see if it will start. If it starts check the other cylinder. If it only starts on one cylinder, the other cylinder is not getting spark or fuel.
Thanks for the reply. I'll check that as you described, I believe it will show it's running on both as the loss of power is sporadic, runs okay then loses awhile, runs okay again.
Ok that definitely rules out fuel solenoid and you're right. If stuck shut it will not even start. If open itll just occasionally backfire when you shut it off. With it going back and forth I'd also rule belts out. Yes I have saw some with little compression loss with no smoke. Now if your valves aren't adjusted right or they are occasionally sticking, it wouldnt smoke. Bad rings and or worn cylinder is when you start seeing white smoke. When it backfires, is it out muffler or carb? Usually backfiring indicates a valve is open when the spark plug ignites and that explosion either comes out of carb (stuck open intake) or out of muffler(stuck open exhaust valve). I had one recently that backfired every single stroke and it ended up that the rocker arm on exhaust came so loose that the exhaust valve never opened. If you have any more questions I'll help you all I can.