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B&S Quantum Engine May Have Governor Problem


jim45's Avatar
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01-14-18, 05:10 PM   #1  
B&S Quantum Engine May Have Governor Problem

I have a B&S Quantum engine on my DR self propelled string trimmer that I was unable to start after using it several times last summer. It appeared to not be getting fuel into the carb. I thoroughly cleaned the carb and it didn't help. If I squirt a little fuel into the carb it will start and then die in a couple of seconds. I found that if I stick the knuckle of my finger into the intake of the carb just below where the air filter sits (with the air filter removed) right after starting it I can keep it running indefinitely, even under load, by using my knuckle as the governor restricting airflow into the carb. I can feel the vacuum pulling on my knuckle which is in turn sucking fuel out of the carb and into the intake path keeping it running. The parts manual shows two governor springs but I can only see one on the engine, the "spring-governor", while the "spring-governed idle" is nowhere to be found and I can't see where it could connect to anything. Can anyone tell me if the second spring is needed, and if so, where does it go? Any other ideas on what can cause a governor to suddenly stop working?

 
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01-14-18, 06:39 PM   #2  
How did you so called "clean" the carb?
Unless you removed and disassembled the whole thing and cleaned with carb cleaner and cleaned out all the ports with a tool made for this it's not clean.
Using Non Ethanol gas?
Big mistake if your not on a tool that gets that little use.
You have a fuel supply issue not a governor issue.

 
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01-15-18, 06:08 AM   #3  
Thanks for your comments. I did completely disassemble the carb and cleaned out each part and all of its orifices and tubes with carb cleaner spray. I don't have any special tool though. I had been using the engine for an hour a day, four days per week for about three weeks when suddenly it just wouldn't start after blowing out all the chaff and refueling. Since it happened all at once, rather than degrading slowly, I thought something came loose or broke. I think the engine has an auto-choke feature since there is no choke lever and that is leaving the throttle wide open even when trying to start which causes there to be no vacuum to suck the fuel out of the carb. I use the only regular fuel available in California with up to 10% ethanol.

 
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01-15-18, 07:49 AM   #4  
The bolt holding the carb bowl on is the main jet it has a hole across the bottom and one down the center it needs to be cleaned I use the wire from a twist tie to clean them. Have a good one. Geo

 
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01-23-18, 08:09 AM   #5  
I made a new discovery that may be the root cause of my engine problem. I discovered that the primer was not injecting fuel into the carb intake. I took everything apart again and the primer seemed to be fine. I figured out that the primer is pumping air into the carb bowl area which should cause it to pressurize and squirt a little fuel through the fuel metering tube that sticks up into the intake area, but it wasn't. Upon disassembling the carb completely I noticed that there was an irregular shaped hole that shouldn't be there from the top of the bowl chamber into the area where the bottom of the throttle shaft rests. This creates an air path from the top of the bowl, where there is no liquid fuel, to the intake area. Thus pushing the primer simply pushes air into the bowl and out the top without injecting fuel into the intake area. This all makes sense since I had originally discovered that the throttle shaft (a plastic part that holds the throttle plate) was broken. I had replaced it but hadn't removed the float so I could see the broken hole into the bowl area. I've ordered a new carb and will install it this week. Hopefully that will fix my engine.

 
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01-26-18, 07:18 AM   #6  
The new carb fixed the problem. An actual mechanical failure internal to the carb was the problem.

 
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