# How to test vacuum fuel pump?



## No_Substitue_For_A_Brute (May 4, 2011)

Can someone help me understand how to test the vacuum operated fuel pump on my 05 750? The manual isn't real clear to me. Picture attached for what it says to do.


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## DaveMK1 (Nov 8, 2009)

from what i gather you blow into A and you should not have air comming from b. If you do the pump could be bad


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## No_Substitue_For_A_Brute (May 4, 2011)

Yea that's what I figured too. Looks like pump is bad then. looks like I'll be hunting for a new pump tomorrow.

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## NMKawierider (Apr 11, 2009)

Yeah they don't speak english very well do thay. Basicly you have a diaphram that pulses back and forth in a chamber that has two checkvalves. When the diaphram moves one way it draws fuel in from the tank, then when it moves the other way that check shuts and the pressure pushes the fuel out the other to that carb...kinda like your heart works. 

So... they want to test that the diaphram isn't ruptured and the check valves work by blowing through these ports and checking the other ports.


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## MetalHeaded1980 (Feb 4, 2012)

I installed a fuel shut off valve in the fuel line coming off the tank on my 06 bf750. I ran the engine and turned the valve off. Motor kept running..... i guess the vacum system on this motor is different than my old 2002 prairie 650. Not sure if there is a way to install a shut off valve in this quad that will work. Anyone know a way? I just want to keep the carbs free of fuel when the quad sits for awhile and suffer ethanol carb damage.


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## NMKawierider (Apr 11, 2009)

MetalHeaded1980 said:


> I installed a fuel shut off valve in the fuel line coming off the tank on my 06 bf750. I ran the engine and turned the valve off. Motor kept running..... i guess the vacum system on this motor is different than my old 2002 prairie 650. Not sure if there is a way to install a shut off valve in this quad that will work. Anyone know a way? I just want to keep the carbs free of fuel when the quad sits for awhile and suffer ethanol carb damage.


Just drain the bowls. Or you can also place a shut off valve just before the carbs and


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## MetalHeaded1980 (Feb 4, 2012)

nmkawierider said:


> Just drain the bowls. Or you can also place a shut off valve just before the carbs and


and.... what? Im not sure where i could put the shut off valve next to the carbs that work better than in the middle of the main fuel line...


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## NMKawierider (Apr 11, 2009)

MetalHeaded1980 said:


> and.... what? Im not sure where i could put the shut off valve next to the carbs that work better than in the middle of the main fuel line...


Then anywhere after the pump and before the carbs.


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## DaveMK1 (Nov 8, 2009)

It's gonna take a while for the bowls to completely empty even when the fuel supply is shut off, that's why your bike kept running when you shut the valve.


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## NMKawierider (Apr 11, 2009)

DaveMK1 said:


> It's gonna take a while for the bowls to completely empty even when the fuel supply is shut off, that's why your bike kept running when you shut the valve.


Yeah and you still won't get it all out that way. Best to just open the drains and be done with it.


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