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Crank but won’t start

Discussion in 'RZR Nation' started by derbyman98, Jan 21, 2019.

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  1. derbyman98

    derbyman98 kenny SXS Nation Regular

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    2012 Polaris rzr 800s

    Hello everyone it’s me again, the last time we rode in the late fall I had an issue. After about a 35 minute stretch of trail we stopped for a break. The rzr sat for about 10 minutes and when I went to start it it just cranked and cranked. It eventually did start but it took a while. Had similar issue before but only took a few seconds to start by holding it wide open while cranking. As always and help is always appreciated
     
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  2. Seastacker

    Seastacker Carl Moderator

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    2019 Polaris General 4

    Does it start now that it’s cooled off ok?
    If so, it sounds like a vapor lock issue where the fuel will get so hot in the lines and fuel system, it will actually vaporize. They will typically re start once they cool a bit. The fix there is typically insulating the fuel lines from heat sources like the exhaust.
    If it’s doing it all the time now or frequently, I would be doing a fuel pressure check to ensure the pump is working correctly. I’m not 100% on your machine, but the spec is usually 39-42 ish psi.
     
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  3. DieselFume

    DieselFume Adam Moderator

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    2013 XP 800 Ranger, Three 2017 Polaris 570 Full Sizes. All subjected to hard ranch work, long hours and rough conditions. 5 years or bust!

    Hi Kenny,

    Carl pretty much hit the nail on the head.

    What you're describing is exactly the type of issues I used to have with my 2011/2012 ranger 800s. It was usually on the hotter days in the summer, but was always after getting the machine fully warm. Engine was hot, engine bay was hot, and the fuel in the fuel tank was hot. Pretty much the perfect recipe for vapor lock.

    What many folks don't know is that having a slightly under performing fuel pump will make the problem even worse, even if you're not noticing performance issues. Spec for the ranger 800s is 39 psi give or take 3 psi. I can tell you that if your fuel pressure drops below 39 psi, you'll notice this problem greatly increases.

    Another way to help remedy a vaporlocked 800 is to cycle the key to on for a few seconds, then off again, to pressure up the pump a few times. Usually this will help build up the pressure in the line, and the engine will usually start after a few quick cycles.

    I would check fuel pressure at the rail and see what yours is doing. If you haven't done that before, just give a shout, I can walk you through it. The pump may test ok at idle, but for a more accurate reading, you should watch the gauge while driving under some heavy throttle conditions to see if the increased fuel demand causes lower fuel pressure.

    If at any time you see it drop below 39, I'd replace the pump. You can get new assemblies from polaris, But also from other places like Quantum Fuel Systems for much less money. They usually sell complete assemblies (which is what I'd opt for) and also just the pump itself.


    Last thing, Gas also makes a difference. If you're using a winter formulated gas sold or purchased during the late fall through early spring, odds are it's a winter formulated fuel which is different than gas sold in summer. Winter fuel has more oxygenates in it which help the engine run during those cold winter starts (it evaporates easier) but during summer, the extra oxygenates actually makes vapor locking issues much much worse... Don't know where you get your gas, but it's one thing to keep in mind.

    Have any pics of the fall trail riding?
     
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