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Vacuum Fuel Pump Question


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#1 dodge trucker ONLINE  

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Posted May 27, 2014 - 07:19 PM

This is a question that I *THINK* that I already know the answer to, but I want reassurance.

 

This Swisher Trailmower I just got has a 14HP Vanguard on it.  Bolted down, pulleys and belts all connected, but it has no gas tank.   I have a tank I want to use but  the only place I can really mount it the bottom of the tank will be even with or lower than the engine sump let alone the carb and fuel inlet. 

Most engines that I see with fuel pumps even, still typically mount a tank so that the bottom of the tank is above the carb inlet  (kinda defeats the purpose of a fuel pump because with that sort of mount  all you really need is gravity)

 

I "could" mount the tank higher as in over top of the engine I guess/ but it would look stupid with the rest of this combination, and it would also tend to get in the way if you wanted to mow around something with low clearance.

this vanguard has the vacuum pulse style fuel pump on it rather than the mechanical style like I'm so used to seeing on cast iron Kohlers and even some of the old Tecumsehs.

The tank I have is an oval style steel one like what used to com on the (way) older Kohlers, it's like 6 qt capacity might even be a 2 gallon.

My plan was to make a mount bracket next to the engine mount base between the belt drive and the wheel.  It would be like a 16-18" run from the bottom of the tank to the fuel pump inlet  about 1/2 uphill.

The fuel pump on this Vanguard should be able to handle that if it is in good working condition, right?

My plan is to use 1/4" steel tube probably like the stuff used for automotive brake and gas lines with just the last 2-3" on each end being rubber fuel line. I did the one on my Woods Zero Turn that way but that one runs pretty horizontal from tank to carb. The other difference is that Woods mower has a cast iron 12 HP Kohler Magnum with a mechanical pump driven from the cam.



#2 olcowhand ONLINE  

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Posted May 27, 2014 - 07:34 PM

I would say you'd be fine.  The only thing may be that the fuel may run back down to the tank, making the engine have to crank longer to get the fuel up to the carb.  If the carb still has enough fuel in it to crank up (not evaporated after a long sit), even for just a few seconds, then the pulse pump will catch up easily.


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#3 dodge trucker ONLINE  

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Posted May 28, 2014 - 05:05 PM

I have looked at pix of other trailmowers since I put this post up, and it seems many have the gas tank mounted the same way that I have in mind....



#4 HDWildBill ONLINE  

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Posted May 29, 2014 - 10:03 AM

I think you will be OK.  Worse case you would have to put an electric pump on.


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#5 Bruce Dorsi ONLINE  

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Posted May 29, 2014 - 01:48 PM

I just acquired a used 44" Swisher with a 10.5 hp B&S engine equipped with a vacuum fuel pump.

 

The bottom of the tank is below the level of the carb, and the vacuum pump is located on the engine shroud above the level of the carb inlet.

 

I believe a siphon effect is created by the vacuum pump.  ....Once the gas gets to the level of the pump, it flows downhill to the carb.  ....The diaphragm in the pump may be acting as a check valve to prevent fuel from draining back to the tank ???


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#6 olcowhand ONLINE  

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Posted May 29, 2014 - 01:51 PM

I just acquired a used 44" Swisher with a 10.5 hp B&S engine equipped with a vacuum fuel pump.

 

The bottom of the tank is below the level of the carb, and the vacuum pump is located on the engine shroud above the level of the carb inlet.

 

I believe a siphon effect is created by the vacuum pump.  ....Once the gas gets to the level of the pump, it flows downhill to the carb.  ....The diaphragm in the pump may be acting as a check valve to prevent fuel from draining back to the tank ???

 

The flap style check valves do hold back gas, but once they get older, they may or may not hold it back very long as they lose elasticity.


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