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Bike won’t start, blown ignition fuse


Tak61893

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So I went to go start my 2018 mt07 after not riding for maybe a week and it wouldn’t turn on. The headlight and taillights all work except the display won’t turn on and it won’t even crank over or prime the fuel pump or anything. Found the ignition fuse 10amp was blown, put a new one in and as soon as I flip the key on immediately pops the fuse. I do have the fender eliminator and intergrated rear tail light but I checked all the wiring and it looks fine, also have a ft Ecu side harness tuner and I even unplugged that to be safe and try it out and same thing. Any suggestions/solutions ?

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Just now, Tak61893 said:

So I went to go start my 2018 mt07 after not riding for maybe a week and it wouldn’t turn on. The headlight and taillights all work except the display won’t turn on and it won’t even crank over or prime the fuel pump or anything. Found the ignition fuse 10amp was blown, put a new one in and as soon as I flip the key on immediately pops the fuse. I do have the fender eliminator and intergrated rear tail light but I checked all the wiring and it looks fine, also have a ft Ecu side harness tuner and I even unplugged that to be safe and try it out and same thing. Any suggestions/solutions ?

There's a short there someplace, find it. Check main frame ground on left rear down tube, recheck all your add on stuff and anything you've messed with. New connector, tie in, bare wire, splice? Pull, twist, tug, dig, it's there somewhere.

Good luck.

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I looked at the wiring diagram, the ignition fuse is connected to a lot of stuff.

The dash,
radiator fan motor relay,
fuel pump relay,
starter relay,
immobilizer unit,
O2 Sensor,
the intake solenoid (perhaps not existing at your bike, euro 3 europe thing i think)
ECU,
starting circuit cut off relay (sidestand up, gear in neutral,...),
the Start/Stop switch (maybe check that this isn't stuck in start position?).


A lot to check if you have bad luck. 
Perhaps it's possible to measure the resistance from the ignition fuses terminal to ground. With a direct short circuit to the frame/ground somewhere you should measure 0-0.3 ohms, for example.  Somebody has to check this value on a working bike with the ignition key turned on (correction: not necessary to have the ignition turned on I think) to find out the normal electrical resistance for you to compare.
Then you can move the harnesses and disconnect things while watching your ohm meter without destroying one fuse after the other.

Just an idea.

You can  also buy automatic fuses with a litte switch, you can reset them after a short circuit.

Or you use a lamp instead of a fuse (H4 from headlight for example), that limits the current and as long the lamp is bright with ignition turned on you have a short circuit somewhere. But this might be a little bit risky at modern bikes, maybe disconnect the ecu, immobilizer and dash first (aka the expensive parts).

Wrote this down very fast, have to pee since 30 minutes  :D





 

Edited by ElGonzales
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13 hours ago, mossrider said:

There's a short there someplace, find it. Check main frame ground on left rear down tube, recheck all your add on stuff and anything you've messed with. New connector, tie in, bare wire, splice? Pull, twist, tug, dig, it's there somewhere.

Good luck.

I had this happen with a car once and they (dealership) did what @ElGonzales suggested to do as a process of elimination to pin down the area in the wiring harness where the short is and they found a wire had come loose. The wind had been blowing the wire enough to move it back and forth and all the insulation had been rubbed off, exposing the wire and causing the short. That would explain the dash, etc not working. GL.

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Beemer

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I did some research.

First of all we have to determinate  which side of the fuse slot connects with the battery / main switch and which is connected with the other harnesses and electrical consumers.

Therefore I removed the fuse and turned the ignition on. As you see, the frame-sided clamp "1"  still has a potential of  ~12V measured against ground ("3", negative battery pole). Yes, I need a new battery.

IMG_20200322_165116_resized.thumb.jpg.33297072e2a2d5c9d91142aa8307132c.jpg


Lets test the theory  the other way around. The ignition fuse powers the coil of the starter relay, so the other clamp of the fuse slot has to have a good connection to the starter relay (red-white cable of the starter relays terminal). The brown cable is connected to the black probe.
Sorry, the red arrows I drew are not good visible.
Yepp, it's close to 0 Ohms, myth confirmed! :

 

IMG_20200322_163449_resized.thumb.jpg.75cd2dd4341d947c694a6093d6db7b04.jpg

 

Now we know which side of the fuse slot is connected with the bikes possible faulty harnesses, wires and components.
We can measure the electrical resistance between this clamp and ground / negative battery pole to have a comparable value of a working bike.
Measure the electrical resistance between the lower clamp and the negative battery pole.

You should see something around 0.725 kOhm (...or 725 Ohm)  if there is no short circuit behind the ignition fuse.
 

IMG_20200322_163712_resized.thumb.jpg.243d36195354cb93eac870ce5d45b97d.jpg

The negative battery pole is connected to the frame (and has to have a very good electr. connection to the frame!), you can also measure from the fuse slot clamp to one of the screws which are turned into the frame:

IMG_20200322_163810_resized.thumb.jpg.432fd95089011aae2cfaab4eb4147122.jpg

 

If we want to make a dirty calculation (naive fallacy on english? ), on the faulty bike there should now be a resistance below 1.2 Ohm to destroy a fuse with a rated current of 10A.
(R=U/I  ---->  12V / 10A = 1.2 Ohm)

I recommend to disconnect relays, dash, ecu, move harnesses etc. and check the resistance while you do this.
 

 

Edited by ElGonzales
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