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B&S 18.5 twin/Fuel flow/Fuel Solenoid/Gas Issue


Tomen8r's Avatar
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07-26-08, 05:16 PM   #1  
B&S 18.5 twin/Fuel flow/Fuel Solenoid/Gas Issue

Iíve got an MTD Yard Machine with an 18.5hp B&S twin. While cutting my lawn, the lawn tractor died. I went thru normal troubleshooting steps, such as checking filters, spark, etc. I did some research and realized that fuel wasnít reaching the carb. I can stand over the carb and manually pour in gas and it will run all day, but the gas isnít reaching the carb on itís own. I have removed and cleaned the gas tank, replaced all fuel lines, replace both plugs, rebuilt the carb with new jets and gaskets and rebuilt the 3 screw fuel pump with all new parts as well. The fuel pump is located on the front of the carb. I can still pour gas in the carb manually, but the gas will not flow on itís own. The last fuel line runs into the block, as the vacuum is provided by the engine. That is clear as well. According to my parts list, I do have a fuel solenoid. I kind of remember hearing it click when I turned the key, but it doesnít click now. My next step is to locate the fuel solenoid, but I can not find it anywhere. Some say to follow the red wire, but the only red wires run to the starter solenoid and the second runs up underneath the flywheel. I donít think B&S would put the fuel solenoid under the flywheel (would they?). Right now, the tractor is just a motor on a frame as I have removed just about all body panels, and I canít find the fuel solenoid. Any ideas out there? I believe the tractor is from either 1997 or 98. I bought it used for 300 clams 8 years ago and it has been running like a champ. Should I be looking for the fuel solenoid? Or do you think it the lack of fuel vacuum would be due to poor oil pressure? Oil looks good, but I am gonna change it anywhere to see if it makes a difference. I need to find the fuel solenoid, but I have looked for a week straight and canít find anything that looks like the pic I have seen. I just know it might have a red wire. Or it might not have a red wire. According to B&S, the solenoid is part number 397266 (part 947A, since itís a three screw fuel pump). Model number and other stuff listed below. Any help would really, really, really be appreciated. I am not a mechanic, but I normally can do this stuff with ease. Help me. Help me. Help me!
Many Thanks,
Tomen8r from Hooksett, NH
M 42A707, T 1238-01, C9608065A

 
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07-26-08, 05:47 PM   #2  
If your standing in front of your tractor facing the engine, and the carburetor is on the front of the engine. It will be located on the carburetor to the right hand side, near the bottom of the float bowl.

You can look at an illustration of your carburetor by downloading a parts list at the Briggs and Stratton website, just enter your model and type info and then look at the carburetor break down, I believe it's reference number 974.

http://www.briggsandstratton.com/mai...nav3&subMenu=3

 
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07-26-08, 05:48 PM   #3  
fuel solenoid should be on the bottom of the carb. on the left hand side of the engine.

 
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07-26-08, 05:54 PM   #4  
Thanks for the quick response! There are no wires that connect to the carb. And no wires that are unplugged that should be plugged into something else. I am guessing that the fuel solenoid would require some type of electrical, right? Maybe? I have already taken the carb off and rebuilt it and there were no wires connected to the carb. There are wires that run around it and up under the flywheel (and the headlight wires), but that is it ..
Tom

 
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07-26-08, 05:59 PM   #5  
If your carburetor is equipped with a fuel solenoid it would probably have a spade connector on the end. You would know it if you removed the carburetor as its a small barrel shaped unit about 1 1/2 inches long, and has a small needle protruding out of the end that screws into the carburetor. It mounts directly on top of the main jet, which is accessed from the side of the carburetor, and if you do not have this solenoid there will be a large bolt with an "O-Ring" seal that screws in to give access to the main jet.

 
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07-26-08, 06:02 PM   #6  
Thanks 30year!

I have been using that site for my parts, but unfortunately, while it shows the fuel solenoid, it doesn't actuall show where it goes, like the rest of the parts. That's why it has been a big mystery to me .. I really hope I am not missing the obvious after all this time! LOLOLololol ... doh .

Thank you!
Tom

 
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07-26-08, 06:07 PM   #7  
Thanks again 30year ..

I believe I do have the o-ring setup on my carb. I did replace that during the rebuild. I will double check in the am when it's light again!

Thanks!
Tom

 
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07-26-08, 06:12 PM   #8  
You are welcome, if you don't have a fuel solenoid then there is still some restriction in your carburetor or the fuel pump may not be delivering fuel to the carburetor.

 
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07-28-08, 12:57 PM   #9  
Thanks guys,

My parts list covers about 10 different model tractors, so I took it for granted that I actually had the fuel solenoid. I do not!! I am going to re-do the carb. If that doesn't work, it could be related to the piston/valve that controls the vacuum for the fuel line.

Thanks again!
Tom

 
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