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2004 Polaris Sportsman 500 H.0
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Discussion Starter #42
well good news, I finished carb rebuild and replaced fuel lines and fuel pump and finally got it going. runs nice and smooth now. Just finished up servicing it. Thought i was done with the problems with it running properly but, have hit another hiccup !!! it will start and idle just fine, throttle is responsive and is not bogging down at all. However, after idling for around 10 min or so it will just suddenly stop running. It will immediately start again but runs for a shorter time and will suddenly stop again.
 

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Sounds like a vacuum lock the fuel tank or the carb float bowl vent - if it is the fuel tank, run with the cap loose (might slosh some fuel out) - or it might be a pinched or obstructed fuel line or petcock
 

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2004 Polaris Sportsman 500 H.0
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Discussion Starter #44
I tried the fuel tank vacuum and fuel lines earlier with no change. is it possible to run the fuel line directly from the fuel tank and gravity feed the carb and test if it will run without stopping ?
 

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2004 Polaris Sportsman 500 H.0
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Discussion Starter #45
one other thing to add, not sure if its related or not. When the sudden shut off occurs it usually happens right after the rad fan stops .
 

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With the fuel tank full, it is gravity feed - the fuel pump is really not doing any work until the tank gets low.

Does it die while going at a steady speed or when you let off the throttle or when you turn to the right? If it dies when you let off the throttle or turn right, put some slack in the throttle - if it dies at a steady speed, rule out a certain electrical problem by disconnecting the black wire at the CDI box.
 

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2004 Polaris Sportsman 500 H.0
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Discussion Starter #47
Its still disassembled so it's only happening from idle. Could you explain more about disconnecting black wire from CDI?

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The black wire it the 'kill' wire - when the black wire is connected to ground either by a switch or short - the spark is squelched - in the case of a wire shorting to ground, it could be momentary depending on the movement of the wire - disconnecting the wire means none of the methods to stop the engine will function until it is reconnected.
 

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2004 Polaris Sportsman 500 H.0
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Discussion Starter #49
ok, am I understanding that the black wire on the CDI box connects to the kill switch? and that by performing this disconnect of the black wire it will keep the machine from stalling if there was a problem with a ground or a short in the kill switch circuit to the cdi?, what would be the best method to disconnect this wire? sorry, just trying to be specific since this is all new to me. I really appreciate all the help though.
 

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Right - if the problem is a loss of spark, you eliminate the switches (all 3), the reverse speed limiter and kill wiring by disconnecting the black wire - if you still have a problem the possibilities are reduced to air, fuel and the ignition system itself
 

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2004 Polaris Sportsman 500 H.0
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Discussion Starter #51
Ok cool. Is there an easy way to disconnect it? From the cdi side or kill switch side?

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Discussion Starter #52
Black wire from cdi plug went to another plug so I just made 2 jumpers and eliminated the black. Still died though. So it's now fuel, air, or ignition?

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Discussion Starter #53
ok, did some more investigation. was inspecting the fuel lines while running the machine. I happened to notice that the fuel level was going down on the fuel filter. out of curiosity I bumped the throttle which filled the filter to full again. It would slowly drain over the course of about 1.5 minutes. I kept bumping the throttle to keep refilling it and had it running for over 30 min. As soon as I stopped bumping the throttle the machine stopped after 5 minutes. Another observation is that when I would bump a little more agressively it would fill the filter and I noticed what seemed to be an air bubble float up to the top of the filter. Would this indicate a vacuum problem , fuel pump problem possibly?
 

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What you did just eliminated the ignition system as the problem - so now it's a fuel problem

Air in the filter only indicates air in the filter - fuel flows right past the air bubble - I think you have a fuel pump problem - I just worked on a 500 that had the fuel pump full of dirt preventing it from pumping adequately

The fuel pump has 3 small 'breather holes in the back plate - the plate covers a diaphragm - the vehicle was ridden for 10 years before the air space behind the plate filled with enough dirt to prevent the spring that pushes the fuel drawn in by vacuum from compressing and extending sufficiently to push enough fuel to the carb at anything above idle.

The first pic shows the amount of dirt in the pump air chamber - in the second pic (if you look very closely) there is one vent hole behind the spring loaded pressure pad and two more holes at the lowest point of the part - two of the holes are almost completely clogged and the one behind the pressure pad is almost invisible from the dirt covering it. If this pump did not also have a pinhole in the diaphragm, it may have been cleaned and put back in service and it would work with the pinhole, but the pinhole allowed it to get a small amount of fuel into the vacuum line causing it to run rich all the time.

Your fuel pump may just need cleaned, but it's faster and about the same cost just to put a new Quantum pump on

142961
142962
 

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Discussion Starter #55
Well, it has new fuel pump but it could be faulty. It was a cheap knockoff I purchased on amazon. I'll clean up and inspect the original and give it a try. Thanks again!

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Discussion Starter #56
ok, just wanted to post an update. Attempted to clean up the original fuel pump but the gaskets were to far gone. The Quantum pump you recommended finally got delivered today. Installed the new pump and I let it run for over an hour without any issues. Im going to returning the cheap knocked off i found on amazon as it was defective. Thanks for all the help and your recommendations, not only does the machine run but I think I have learned more going through this.
 
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