Engine Surging

Old 11-29-02, 07:01 AM
J A Boggan
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Question Engine hunting

What are the common causes for an engine to "hunt" or "surge"...it is a problem I run into often.
Old 11-29-02, 09:13 AM
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I would say carburetor issues...dirt, junk in the carburetor necessitating a rebuild.

I think 50% of the small engine problems seen today are carburetor related...trash in the carburetor, stale fuel sitting there and attacking the gaskets, clogged fuel lines, etc. The AYP/Craftsman mower I found recently was thrown out due to a stuffed fuel line (at least mechanically). I do have to rebuild it to get it working 100%, but by simply cleaning it, I got it to idle and run.

I find that most times it's fuel related more than coil/spark. Solid state/electronic ignition is pretty reliable on most makes.
Old 11-29-02, 12:18 PM
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Arrow Engine Surging Possibilities

Hello: J A Boggan

Typical and most common engine surging can be related most often to lean carburetor settings or carb problems.

Improper governor adjustments, dirty, rusted, corroded or damaged linkage can cause this problem as well. Governor springs can also be the problem as well.

Imcorrectly or improperly reinstalled and located governor linkages and or springs can cause the problem. Recheck the parts to insure they are installed correctly and not possibly crossed in the governor lever holes or on the carb body throttle plate.

Anything fuel related can cause engine surging, idling & running problems like or similar to your problem description.

I would first suggest trying an adjustment to the carb screws to richen the fuel to air mixture. A richer mixture can resolve the problem but not if the carb fuel passages are restricted.

If a carb adjustment fails, check all fuel flow related items next.

Fuel flow out of the tank.
Tanks vent hole in the cap.
Fuel line and filter.
Carb float may be sticking or stuck.
Check the carbs bowl fuel level.
Plugged and or restricted carb internal fuel passages.

Valves and governor parts can also cause this type of problem but are far less likely to be the cause.

If no problem with any fuel flow is determined and no carb adjustments correct the problem, the carb will have to be cleaned out. New rebuild carb parts installed and adjustments made.

The other resident small engine service and repair professionals may offer additional suggestions, advice & help.

Regards & Good Luck, Tom_B.
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Old 11-29-02, 01:28 PM
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The most common source of surging in most any engine is vacuum leaks. Air getting into the engine through other area other than the carb. Broken or corroded hoses mostly.
Old 11-29-02, 01:29 PM
J A Boggan
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Thanks Joe & Tom for your expert opinions. This problem seems to come in spurts...and what that will work for one desen't neccessarly work for another one.
Old 11-29-02, 06:28 PM
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I totally agree with you Tom, very good answer.

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