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2008 KFX450r
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Discussion Starter · #1 ·
Hey guys so recently been having electrical issues from hell with my kfx. First it lost fuel pump prime. Kept running around in circle testing everything with no luck. Tested my tps voltage and signal. Made sure every relay clicked not just the fuel pump relay. Tested my crank pick up to make sure it was picking up with no broken wires or anything. Took the stator cover off to see if there was a blockage with the pick up. Replaced the entire wiring harness because there were a bunch of sketchy things done by the original owner regarding wiring. Cleaned every single connector on the machine. Cleaned fuel pump ground to metal assembly and all connections internally. “Bench” tested fuel pump with a power probe. Almost anything I’ve read and thought to test or check. Anyone else lose spark and fuel and have nothing fix it? The only thing I’ve found is a broken red with black tracer wire inside the head light switch that runs from the handle bar switch back to the tail lights and I do not see how that would affect it. Help is always appreciated. Thanks guys.
 

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Discussion Starter · #3 ·
The vehicle down sensor if out of range or faulty will shut down your spark, fuel & injector...!!!

So check/test the output voltage of the vehicle down sensor...!
I will check it again. I had checked it before and it was in range and my harness came off a blow up parts machine and ran up til it blew up from what I was told. It came with all 4 relays, the brake light sensors, (front and rear) the vehicle down sensor, and the clutch safety sensor.
 

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I will check it again. I had checked it before and it was in range and my harness came off a blow up parts machine and ran up til it blew up from what I was told. It came with all 4 relays, the brake light sensors, (front and rear) the vehicle down sensor, and the clutch safety sensor.
I recommend a new oem start switch/headlight switch.
 

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2008 KFX450r
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Discussion Starter · #6 ·
I recommend a new oem start switch/headlight switch.
Got the new switch finally. Nothing changed. Fixed my neutral/reverse indicator. Lost the spring a while back. It always ran good so I never worried about it. Put the new spring I had for it whenever I felt like putting it in and nothing changed. I was thinking maybe air temp sensor is bad?
 

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You sure you don't have NO spark or injector spray.?

Try starting it, pull the spark plug check for being wet with fuel

If fuel soaked, your water temp sensor might be faulty

Do you have 12v on the Y/R wire to frame ground at the ignition coil?

And do you have 12v on the W/R wire to frame ground at the fuel injector?

If you have voltage, the negative pulse/fly back circuit might be bad, thus Bad ECU.

or your valves need to checked & adjusted?

Do a compression test 49~81 psi useable range!
 

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Did you figure it out? My quad just died in the middle of the ride the other day and fuel pump won't prime any more when key is turned on. I'll dig in in a couple of days to try and figure it out...

BTW - if you have one of those small orange fuse boxes you don't need from the spare harness I would like to purchase if you are willing to part with it...
 

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Could be a bad ECU. My bike was doing the same . Over $400 on Partzilla because Rocky Mountain atv was on backorder. Just keep throwing money at it 🤣
 
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2008 KFX450r
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38 Posts
Discussion Starter · #12 ·
You sure you don't have NO spark or injector spray.?

Try starting it, pull the spark plug check for being wet with fuel

If fuel soaked, your water temp sensor might be faulty

Do you have 12v on the Y/R wire to frame ground at the ignition coil?

And do you have 12v on the W/R wire to frame ground at the fuel injector?

If you have voltage, the negative pulse/fly back circuit might be bad, thus Bad ECU.

or your valves need to checked & adjusted?

Do a compression test 49~81 psi useable range!
Voltage for y/r wire at the coil matched my lithium battery at 13.0 volts. But the injector w/r wire was dead.
 

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Discussion Starter · #13 ·
Could be a bad ECU. My bike was doing the same . Over $400 on Partzilla because Rocky Mountain atv was on backorder. Just keep throwing money at it 🤣
Might throw a pro com ecu on it for more tunability and it’s like $250.
Did you figure it out? My quad just died in the middle of the ride the other day and fuel pump won't prime any more when key is turned on. I'll dig in in a couple of days to try and figure it out...

BTW - if you have one of those small orange fuse boxes you don't need from the spare harness I would like to purchase if you are willing to part with it...
I didn’t yet and I believe I do I’ll have to check.
 

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Discussion Starter · #15 ·
Thank you. I have 2 roll over sensors. The one is original and the other is off a spare harness I have and I tested them both for voltage and both of them came out to have 0 voltage.
 
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