no fuel in carb bowl

shep · #1 Jun 24, 2006, 03:07 PM

I recently obtained a briggs and stratton 20hp riding mower that wont run. Free of course. The original owner said it quit running one day while cutting the yard. I took the carb apart and cleaned it. It was reinstalled and an attempt was made to crank it. When it did not crank, I squirted gas in the carb and it started but went dead. It will run as long as gas is squirted in the carb. The fuel line is clear to the fuel pump at the front of the carb. The fuel pump is square with 4 screws holding it to the carb. After running the engine a few minutes by the squirt method, I pulled the top of the carb off and found no fuel in the bowl. I put a different carb from another mower on it and got the same results, it will only run if gas is introduced in the carb. I believe I have narrowed the problem down to what ever makes the fuel pump work. Is the fuel pump operated by vacuum? What creates the vacuum? That may be my problem. There is 5/16 hose that runs from the rh side of the fuel pump to the block. Is this a vacuum hose that operates the fuel pump?

thebriggsdude · Jun 24, 2006, 10:29 PM

Yeah, it runs off of vacumme..... Sounds like the pump itself isn't up to par.

shep · Jun 25, 2006, 08:26 AM

where is the vacuum generated from? and how do you repair it?

rickdb1 · Jun 27, 2006, 01:11 PM

"There is 5/16 hose that runs from the rh side of the fuel pump to the block. Is this a vacuum hose that operates the fuel pump?"

Yes, that is the hose that carries vacuum to operate the pump. The pump operates from vacuum pulses from the engine block when it's running. If you were to run the motor and had that hose disconnected at the block, you would feel vacuum pulses if you put your finger over the hose nipple on the block. The fuel pump has a rubber diaphram inside it that moves back and forth from these pulses and draws in fuel for the carb. Take the pump apart and check it out. They are really very simple. Most lawnmower repair shops will have the pump or parts to repair the pump. Cheap, too...Make sure you have cleaned the carb well. They can be clogged even though they look clean. Make sure the float needle is moving freely(Not sticking) and opening to allow fuel to flow into the bowl. Did you clean all the passages in the carb. with spray carb cleaner and blow them out with compressed air? A carb. rebuild kit should also be used in conjuction with the cleaning....



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