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Thread: 09 750 Brute force wont start

  1. #16
    Join Date
    Apr 2012
    Location
    MI, USA
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    3,247
    Alright, that confirms the fuel relay is receiving power, but sounds like it's not passing power though it on the switch side.

    Also side note, your battery is pretty low, if you have a battery charger, charge it back up to keep the battery healthy (normal fully charged is 12.6v and completely dead is 11.4v). If the battery gets too low of voltage, it degrades it's capacity over time.

    Since the battery is quite low, it's possible the relay is good but doesn't have enough power from the battery to operate correctly, but it seems like the relay is the likely cause of the issue.



    A new relay from Partzilla is $28.17.

    https://www.partzilla.com/product/ka...0dd6ee0c509962



    There is a way to "bench test" the relay off the bike, but it requires wiring up the power side to test the switch side. Also, appears there's 4 of the same relay on your machine. According to this page relay "B" is for turning on the radiator fan, so if you swap it with the fuel pump relay you should be able to hear the fuel pump kick on and I'd think you could start the machine with it removed. Clearly don't run it for too long with the radiator fan disabled. If you don't recall hearing the radiator fan kicking on recently, it's possible it's relay could be bad too, just something to keep in mind. You could also pull one of the starter control relays, but you likely won't be able to start the machine with them removed.

    Below are the instructions for testing the relay if you want to give it a shot. I'd say to use a fully charged battery to test it though.


  2. #17
    Join Date
    Feb 2011
    Location
    fingerlakesny
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    2,695
    I have other relays I will try and charge the battery up. Thanks so much .
    our original 85 we bought new, 2 - 86 police specials
    250r dust runner
    04 Yamaha kodiaK 450 snowbuster ! Brute Force 750 dust collector .
    Bunch of es stuff I been buying for next builds....
    Gone but lives on in my aching body the mighty 350x collection .

  3. #18
    Join Date
    Jul 2005
    Location
    Manheim PA 17545
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    4,888
    By chance are your fuel or vent lines crushed? Thus would happen alot on kfx700s if guys didnt remember how the lines ran.
    1992 TRX250X
    2005 KFX700
    2001 Blaster w/tri moto 200 motor
    2015 Rancher 420 dct eps irs

    Coal Country Rider

  4. #19
    Join Date
    Feb 2011
    Location
    fingerlakesny
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    2,695
    Vent line goes into frame so no chance unfortunately .. I charged the battery up good and tested the relay and it read .00 so if I remember correctly that should be good but still no start
    our original 85 we bought new, 2 - 86 police specials
    250r dust runner
    04 Yamaha kodiaK 450 snowbuster ! Brute Force 750 dust collector .
    Bunch of es stuff I been buying for next builds....
    Gone but lives on in my aching body the mighty 350x collection .

  5. #20
    Join Date
    Apr 2012
    Location
    MI, USA
    --
    3,247
    Just for a sanity check, can you put your meter in volts mode and check the two probes at the fuel pump (key on, relays installed etc)? FYI, you can disconnect the fuel pump wires for the test. Meter might read a negative number, but that's fine, just means the polarity is backwards for the power on the bike vs the lead hook ups. If everything on the bike is working right, you should have voltage there.

  6. #21
    Join Date
    Feb 2011
    Location
    fingerlakesny
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    2,695
    For some reason I cant download the service manual, I have 4 wires on my fuel pump connector a white/red, a blue , a black with narrow yellow line and a black with a thick yellow line . could you please let me know which ones to check
    Last edited by dustrunner; 07-30-2019 at 09:43 PM.
    our original 85 we bought new, 2 - 86 police specials
    250r dust runner
    04 Yamaha kodiaK 450 snowbuster ! Brute Force 750 dust collector .
    Bunch of es stuff I been buying for next builds....
    Gone but lives on in my aching body the mighty 350x collection .

  7. #22
    Join Date
    Apr 2012
    Location
    MI, USA
    --
    3,247
    Try this link, both work on my computer, but this should be the direct link to it.

    https://web.archive.org/web/20120904...-09_Manual.pdf

    Anyway, the wire diagram only shows two wires to the fuel pump but the two wire colors are Black/Yellow and White/Red. I scanned over the wire diagram and found a blue wire and followed it, it ends up at the Crank Sensor which shows 2 wires, Blue and Black/White on the sensor side, and on the harness side it shows as Blue and Black/Red.

  8. #23
    Join Date
    Feb 2011
    Location
    fingerlakesny
    --
    2,695
    Got it, thank you
    our original 85 we bought new, 2 - 86 police specials
    250r dust runner
    04 Yamaha kodiaK 450 snowbuster ! Brute Force 750 dust collector .
    Bunch of es stuff I been buying for next builds....
    Gone but lives on in my aching body the mighty 350x collection .

  9. #24
    Join Date
    Feb 2011
    Location
    fingerlakesny
    --
    2,695
    Fuel pump connection Reads 11.23 volts with key on and battery reads 12.20 volts
    our original 85 we bought new, 2 - 86 police specials
    250r dust runner
    04 Yamaha kodiaK 450 snowbuster ! Brute Force 750 dust collector .
    Bunch of es stuff I been buying for next builds....
    Gone but lives on in my aching body the mighty 350x collection .

  10. #25
    Join Date
    Jul 2009
    Location
    South Florida
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    5,940
    1 volt drop is about right at the pump with the motor not running , like I said in post # 7 the pumps are know to go bad


    Quote Originally Posted by dustrunner View Post
    Fuel pump connection Reads 11.23 volts with key on and battery reads 12.20 volts
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  11. #26
    Join Date
    Apr 2012
    Location
    MI, USA
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    3,247
    Interesting, assuming enough amperage is getting to the fuel pump, it sounds like it should be running. Maybe the replacement one is defective?

    For the voltage seems quite low at the fuel pump like there's a bad connection along the way, but it should atleast do something I would think.

    EDIT, just saw the other reply, maybe the 1v drop is normal, I don't normally work on machines with so many switches and such lol.

  12. #27
    Join Date
    Feb 2011
    Location
    fingerlakesny
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    2,695
    Shouldn't the red/white wire have more volts than .04 at the relay ?
    our original 85 we bought new, 2 - 86 police specials
    250r dust runner
    04 Yamaha kodiaK 450 snowbuster ! Brute Force 750 dust collector .
    Bunch of es stuff I been buying for next builds....
    Gone but lives on in my aching body the mighty 350x collection .

  13. #28
    Join Date
    Apr 2012
    Location
    MI, USA
    --
    3,247
    As long as you tested between the two wires going to the fuel pump, it's seeing power, and that power comes from the relay.

    Anyway, back in post #15 you mentioned the 0.04v on the red/white wire, then #17 you said you'd charge the battery and you have spare relays. In #19 you tested the relay and the test showed good, was this the org or spare relay? I figured either the fully charged battery, or the relay swap would get power to the fuel pump, so that's why I asked to validate if it's getting power or not.

    Speaking of the fuel pump with it disconnected, can you get an ohm reading between the two wires that normally power it? It should be a low reading, like 1-10 ohms. If it's bad (electrically) it will read either very high, very low (like 0 ohms/dead short), or no reading at all (broken wire internally). It's also possible the motor could be physically bad in some way. Don't know how the fuel pumps are assembled so can't advise much on checking the brushes and such, on a starter it's fairly simple but a fight to get it back together. Also, since you have a cheap replacement fuel pump too, you could take a reading off it too to see if they are similar or very different. Not sure if the service manual has an ohm spec for the motor.

    Another test you could do is to pull the fuel line off the injector fuel rail (or whatever it hooks to for the injectors). It should pump gas with the key on. Service manual says it should put out 1.7oz or more in 3 seconds.

    Also another thing I thought of that I saw in the service manual, be sure not to give the quad any throttle while cranking or you could flood it. Fuel injection is much different than carb in that respect. Not sure if the ATV's have a "clear flood" mode or not, on a car you can floor it 100% and it will turn off the injectors to simulate giving the carb some throttle to let more air in. Could also check the spark plug to see if it's wet, also while you're at it, could check if it has spark. Never hurts to be sure.

    While I'm scanning over the servie manual for fuel pump ohm specs, another good point is to make sure there's enough fuel in the tank. Doing the fuel flow test should also help check if the filter is plugged up, and looks like there's also a fuel pressure regulator which could also get clogged.

    Also, it sounds like it's possible the ECU can throw codes, I found a section detailing the signal and what it means, but it just mentions using a tester to get the codes.

    One of the error codes has a side effect of turning the fuel pump off. The service code is #31 for the Vehicle-down sensor.

    Here's a thread talking about the service codes, sounds like it's not exactly easy to read. Based on the amp specs I saw, sounds like a simple LED would work as a visual way to see the peaks. This info is on page 102 of the service manual. Long peaks = first number, short peaks = 2nd number, long delay per code. Pretty similar setup as OBD1 systems in 1995 and older cars where you jump a couple pins in the diag port and count the flashes of the check engine light.

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