How to bypass B&S twin opposed fuel pump

Geoff813

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Jul 4, 2015
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This 16 hp machine eats pump diaphragms yearly due to what passes for gas here in NH and since the gas tank is higher than the pump inlet Id like to bypass it entirely and not get gas into the crankcase. Can I just clamp off/block that vacuum line or is it more complicated?

Geoff
 

tom3

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I think the crankcase is actually vented through the air cleaner, but to be safe I'd probably leave the vacuum line attached to the pump and just run the fuel lines together. Not real sure how the pump gets any vacuum out of a crankcase anyway. Fuel pressure is about nothing anyway so the gravity feed should work with a nearly full tank.
 

Rivets

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This may or may not work. The thing people don’t realize is that there are different carbs and needles when you have engines with or without pumps. Some need the pressure of the pump to keep the proper amount of fuel in the float bowl. The pump supplies more pressure that most people think, plus may be needed if the unit is used on hills and slopes.
 

Geoff813

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It is my understanding that these engines get fuel pump vacuum from a port on the block and the crankcase breather is what goes to the air cleaner.
Similar to my 68 Impala SS 396 ragtop:smile:
 
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