18 HP Briggs & Stratton Twin Fuel Problem

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  #1  
Old 08-07-09, 09:11 AM
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18 HP Briggs & Stratton Twin Fuel Problem

Hello,

I have searched thru the threads and come to a few solutions but wanted to get other possible ideas. Here’s the issue

Model 422707
Type 121401
Code 9310295A
18 HP

On a 1989 MTD GT 1846 Lawn Tractor.

The tractor has been sitting a while, I just got it yesterday.

I can get the motor to run if I pour gas down the throat of the carb. This prompted me to check the diaphragm mounted on the side of the carb. I have replaced the diaphragm, the hose connecting the bottom port to the engine, and a new fuel delivery hose siphoning out of a can for now.

Still cannot get the pump to pull.

I have also removed the top of the carb, clean out the bowl, check the float seemed ok, replaced the need on the float.

My question what does the bottom hose connection do, I have read I am suppose to use worm clamps here as opposed to the standard spring clamps I have not done this yet but will do so tonight. Does this hose provide additional vacuum to suck the fuel from the tank?

I have also read about the main jet being clogged on the side of the carb, its covered up with a 5/8” Plug, I will take a torch tip cleaner and try to clear it as well. I have a new main jet in the carb kit but didn;t repalce it yet may do that in liue of cleaning main jet dunno depends if I can get the old jet out.

Thanks in Advance for replies. Beer 4U2

Birge
 
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  #2  
Old 08-07-09, 11:36 AM
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If you have fuel in the bowl then the diaphragm is not the problem. Clean or replace the main jet.

If you are not getting fuel to the bowl, make sure the inlet is clear. Best to remove the carb, then float and needle and pump diaphragms, use carb spray and spray and clean through where the needle goes. Best to clean the rest of the carb as well to save doing it later.

The bottom hose supplies vacuum and pressure to the diaphragm in order to pump fuel. The hoses should be a snug fit but I have found no need for clamps of any kind. The diaphragm has such little surface area and travel, it does not take much for it to operate.

It sounds as though you do, but make sure you have the fuel line to the correct inlet and the crankcase hose to the correct fitting.
 
  #3  
Old 08-07-09, 12:00 PM
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I don't have fuel in the bowl, thats why I was in question about the diaphragm pump but it makes sense that theres crud built up there too. It got drak on me last night before I coauld push it into the garage.

If Cleaneing and rebuilding doesn't work and it turns out to be vacumn related, how does one fix this. Or I guess leading to the question what makes this vacumn at the connection to the engine?

I guess we'll rebuild first and see if that sovles it. Also yes I have the fuel inlet hose on the horizontal port , and the vacumn on the vertical port

Thanks for your reply.

Birge
 

Last edited by Birge; 08-07-09 at 12:05 PM. Reason: spelling and me being stupid
  #4  
Old 08-07-09, 12:22 PM
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You probably won't have to worry about a fix for the vacuum. A pulse pump is driven off the pressure variations in the crankcase. A negative pressure is generated with the travel of the piston upwards and the positive pressure is generated with the downward travel of the piston as well as the blow by gasses (somewhat) from combustion.

If the piston is going up and down and the rings aren't completely gone, you will have those variations in crankcase pressure. You can make some exceptions to this with certain mechanical failures, but for the most part this is the case.
 
  #5  
Old 08-07-09, 12:40 PM
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I kinda thougth that after I posted , it wokrs off the crank pressure, and your right if it runs, then this shuld be an issue, most durely its plugged up ports.

Thanks

Birge
 
  #6  
Old 08-10-09, 08:34 AM
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Thanks
Dissassembled Cleaned it out, runs like a top thanks Guys


Birge
 
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