Craftsman GS6500 loses power when mowing

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  #1  
Old 08-15-15, 12:12 PM
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Craftsman GS6500 loses power when mowing

My tractor has a 26HP Kohler Command Pro (cv730s) and is around 9 years old. Mowing the other day and tractor began "lurching" and cutting out when the deck was engaged. I took the deck off, cleaned it and made sure the spindles were spinning freely. Before attaching the deck, restarted the tractor and took it for a spin. Everything seemed ok except the engine still had a faint sputter to it occasionally. Re-attached deck, fired up tractor and and same power loss when deck engaged. Cleaned carb inside and out. Checked fuel solenoid and heard audible click when switch turned to run. Still no power under load but will start fine. Vacuum fuel pump does spit out gas as the tractor is turned over. Two weeks ago I'd installed new fuel/air filters and spark plugs along with changing the oil. Tractor mowed fine afterwards. A week ago, I'd been out mowing and came in to refuel. Shut down the tractor, refueled and went to start it back up but it would not fire. Let it set for a couple of hours and it started right up and I finished mowing. Then a couple days ago is when the power loss occurred and has been that way since. Would anyone have ideas as to what the problem is? Thank you for the help.
 
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Old 08-15-15, 06:01 PM
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Does applying partial choke help?
 
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Old 08-15-15, 09:04 PM
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Hi Cheese and thanks for the reply. If I apply partial choke it just bogs down as if it were going to die.
 
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Old 08-15-15, 09:23 PM
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Might check that it is firing on both cylinders. have a good one. geo
 
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Old 08-16-15, 12:42 AM
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I agree.
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Old 08-17-15, 10:50 AM
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lines

Could be the fuel lines failing inside.
 
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Old 08-18-15, 06:54 PM
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Thanks guys, I'll do some more checking. So what would be acceptable output of the vacuum fuel pump? When I disconnect the fuel inlet line at the carb and turn the engine over I get fuel flow but the flow doesn't stop (after the engine stops turning) unless the line is held above the gas tank. Is there a check valve or something in the pump that would stop the fuel flow when the engine stops or is it free flow with assist from the vacuum pump when the engine is running?
 
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Old 08-19-15, 12:28 AM
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There is nothing in the pump to stop the flow of fuel through it.
 
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Old 08-19-15, 11:15 AM
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You can't tell if they are failing by letting fuel flow out. It happens only under running conditions.
 
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Old 08-20-15, 07:48 AM
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Geo said to check fire. I agree, but with the engine running pull one plug wire off and see what happens. Put wire back on then pull the other one and see what happens.
 
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Old 08-20-15, 06:30 PM
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Thanks guys. I've pulled the individual plug wires one at a time while running and there is noticeable difference in the sound between 2 vs 1 for either side. I will say though that it wasn't as different as I thought it would be. Would it be a weak spark to both cylinders?
Thanks again for the input!
 
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Old 08-21-15, 12:53 PM
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I doubt weak spark. Wanted to make sure you were running on 2. Fuel lines are cheap. Change all of them and see. BikerBill had the same problem and it was a cure.
 
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Old 08-21-15, 07:33 PM
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It could be the fuel lines collapsing, hard to know. The safest thing would be to replace the lines. You could use a fuel pressure gauge to see what is happening during the times it cuts out.
 
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Old 08-24-15, 06:56 PM
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Checked the spark again and found one of the original spark plugs was showing a yellow spark while the other was blue. I got the same yellow spark from the same plug on hooking it to both coils. Swapped the plug for a new one which show a blue spark. Installed new plugs in the tractor and it came back to life with power to mow. Was this the problem? Seems like it. Don't know why cause I figured a spark was a spark. Any ideas on what happened? Thanks to all for the input.
 
  #15  
Old 08-25-15, 11:01 AM
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Yes plugs can go bad. I change mine once a year.

I said earlier I doubted weak spark but I meant the coils. coils can break down also running at higher speed but they quit throwing spark to the plug.

For some reason I thought you said you had new plugs.

Glad you got it going.
 
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Old 08-25-15, 06:30 PM
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Yeah, I'd changed the plugs out a month or so earlier. Forgot the name of them but they were what sears had carried. I replaced these with champion.
 
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