Engine surging

sqzdog

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I have a Craftsman zero turn mower that I bought new in 2012. It has a B&S 24HP V-twin (Model# 4456770954G5) The engine keeps surging and then cuts off. It will start back up after cranking for a few seconds, but then stalls again. Happened mainly when I've been mowing for awhile, but now even when the engine is cold. Here's a link to a brief video clip of the problem: Surging video

Here's what I've done so far:

  1. Replaced fuel
  2. Replaced fuel filter
  3. Replaced air filter
  4. Replaced gas cap
  5. Replaced spark plugs
  6. Rebuilt carb
  7. Replaced carb with new one in case the rebuild didn't fix the problem
  8. Replaced both ignition coils
The last thing I was going to replace is the fuel pump, which should arrive tomorrow. I don't know what else to do at this point. Any advice?
 
Last edited:

Scrubcadet10

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surging is a running LEAN condition, which means more air is entering the combustible mix than gasoline,
I'm willing to bet there is a gasket leaking at the intake on one or both of the heads, or at the carb, or a crack in the intake manifold.
I use WD40 in a trigger spray bottle and with the engine running, saturate around the carb and intake manifold and cylinder head area's. if the engine blows any smoke or changes speed, you have a air leak causing it to surge.
It also looks to be plastic so i would remove it and check it for splits or cracks, even a small hairline split can cause problems.

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bertsmobile1

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Take the blower housing off & start the engine
Hold the governor link or arm which ever you can get to in a fixed position then slowly move it to speed the engine up
If it runs fine then starts to miss & dies then turn it off and allow the engine to cool .
Get a trigger sprayer or pump up bottle with WD 40 or similar solution in it do not use a pressure can or propane gas.
Start the engine again and hold he throttle as fast as the engine will run without without misfiring
With your other hand start to saturate the manifold area and the top of the carb with the WD 40 .
If the engine suddenly blows smoke or changes speed then you have found a manifold leak.
The plastic manifolds fitted to the domestic models suffer warpage & leaking a lot more than the aluminium ones.
 

Hammermechanicman

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Pull the fuel pickup out of the fank and check for grass or crud in the fuel pickup. Remove the fuel line from outlet side of fuel pump and crank engine. Should get good pulsing flow from pump.
 

sqzdog

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Thanks to everyone. I will work on these suggestions and report back.
 
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