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Hi everyone, I am a small engines teacher for a high school, mostly we work on Briggs and Stratton engines.

I have been given a 1997 Formula 500 for students to play with. I am not that familiar with Skidoo or their fuel pumps which is the issue here ( a little of both, me and the pump I am afraid).

We can run it using starting fluid/gas sprayed into the carb but not with the pump. We have verified there is vacuum and pressure with a gage on the pulse line, so the engine is creating a pulse.

We have taken the pump apart and cleaned it (rebuild kit is on order) and bench tested it and it seems to pass. But no matter what we do, it does not pump.

I took the pump out and put it on the bench, connected it to fuel and blew and sucked on the pulse line and can get some fuel to move up the outlet tubes towards the carbs but never filling the tubes or reaching the top of each tube; so it seems like it can't push fuel.

Fuel gets pulled into the pump on each suck, but then some gets pushed out back towards the tank on each blow. This behavior is counter to what I feel it should do as it won't push fuel towards the carbs. The valves don't appear to be damaged or not working. The valves are clear plastic. Could it be the plastic is worn out and is not allowing a seal?
 

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Create a seal with your hand over the gas tank. (With the fuel cap off)

Blow into the gas tank you should have fuel enter the lines. Hopefully pushing any air out as well.

Reading your post looks like you did that just more sophisticated. If the pump won't draw fuel on its own it likely will need rebuilt and should be okay after assuming all your lines are satisfactory.
 

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Aside from the pump being assembled wrong after the cleaning, which is unlikely as they are pretty simple but it is possible, the bellows in the pump may just be worn. Most times a rebuild kit will take care of things. I have seen rebuilt pumps just refuse to pump and were replaced with new pumps that worked fine.

May I ask where you teach....maybe city and state if you dont want to be too specific or you can send a message. We have a son in a program that sounds identical.

Sent from my SM-G996U using Tapatalk
 
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