absolutely no spark and cant work out why - calling electrical whizzes

[doingitdeeper]

Hello. Long time lurker and hoping that theres still enough people on this board to help me out. I always prefer forums as it is, but here goes..


99 fzs600 with no spark. I have absolutely ran out of ideas why. I bought it with no spark, the previous owner gave up.


I have:

• two igniter boxes
• new plugs
• new leads
• new coils
• tested pickup coil - 260ohms
• loop plugs x2 in place under the seat
• replacement loom, all continuity tested, all plugs clean
• anything that would kill the spark has been tested and proven to work (kickstand, clutch switch, cutout switch)
• every wire going into the igniter box has been continuity tested to where it ends up, via the haynes mnaual
• new battery

I have 12v at the back of the coils with ignition on.


clean earth points.


absolutely stumped but i have three really important questions:

• The two white plugs under the seat with looped connections - one of the plugs has four connections, but only two are looped. Is this correct?
• Is there a way to bypass the ignition cutoff relay in order to rule it out? It HAS failed some of the tests in the haynes manual but from reading the diagrams it seems to just send 12v to the igniter box anyway, which it does.
• Pickup coil reads 206ohms and jumps to 260ohms when ignition is on. When it picks up a signal from the rotor, it only moves around about +_20ohms. Is this correct?

As you can see i am knee deep in this thing at the moment and am stumped how something so simple can refuse to work.


The bike is mostly in bits as a winter project and as such i have great access to everything.


Thankyou in advance for any replies!

[BBROWN1664]

Things like the kill switch, side stand and clutch switch stop the starter turning, not the spark so if its turning over, its not them.
Are you getting a supply to the low tension side of the coils? If not then CDI unit and/or a fuse and/or one of the loom connectors between the coils and the CDI.

[doingitdeeper]

Hello, thanks for the reply.

Yes both terminals on the low tension side of the coils are getting 12v.

It appears everything is well except for the cdi unit discharging it's capacitors. To me, all that points to is either the pickup coil (could be wrong, I can't find anyone else's readings anywhere for a working one) or the cdi unit itself.

When spinning the starter the voltages at the low tension side never stray from 12v on the wires coming from the cdi unit.

However as I have two, the previous owner bought a new one to try and rectify the fault, I kind of saw it as a little unlikely. But never say never!

Does the main relay simply provide 12v to the CDI unit and that's it?

[BBROWN1664]

With a constant 12v there (have you checked AC voltage or an oscilloscope as it may be switching too fast for your DC range to react) then it could be the CDI not registering the sensor or its knackered.
There is a guide in the Yamaha manual (download section) telling you how to test the pickup sensor.

[doingitdeeper]

Thanks I'll give that manual a go tomorrow. I don't fancy putting it through my scope in case it decides to fire and fries it haha

With me having two cdi units and neither work I'm inclined to believe it's between the pickup sensor and the relay, if it indeed does more than supply 12v to the CDI unit. There's a few diodes in there I think are passing current where they shouldn't. I'm going to disassemble it tomorrow and test the diodes and resistors inside too.

Thanks, will update.

[unfazed]

The wiring diagram in the Yamaha manual and Haynes manual are have a few mistakes. I put up the corrected Yamaha one in the downloads section some time ago.  I put up the corrected Haynes one up just now. 

A few questions,.
Have you tested the connections in the  ignition switch? They have been know to fail from corrosion and wear..
What tests did you carry out on the Starter cut out relay? A common failure if someone attempted to hotwire it.
.Does he engine turn over?
.Does the neutral light work?

[doingitdeeper]

Hi there

I've just dismantled the relay. It's basically two bog standard relays, three diodes and two resistors. All fine.  I had carried out the tests detailed in the Haynes manual, the most of which are continuity between certain pins. It failed a lot of them where it's "out your probes this way, you should see resistance. If you reverse the probes and get anything other than open circuit it's broke".

However it does it's job by supplying the correct 12v and the relays work too. Testing the diodes and resistors on the board revealed they were doing what they were supposed to be doing.

Relay:
https://ibb.co/XybG1t5

There was a wire off on the barrel when I got the bike, so I had to drill the security bolts out and resolder it. Barrel all fine.

Yes neutral light, it cranks, everything else works. As above all cutout switches work and are correct

I've ordered another CDI box today and on the hunt for a pickup coil but they aren't easy to find. That's about all I have left.

If I wave a screwdriver across the pickup coil whilst cranking it doesn't fire. The resistance only drops from 206ohms to 180ish too. It looks clean and fine but I suspect that's the issue

[Gnasher]

I my experience Fazers don't suffer serious electrical faults, I've never replaced a CDI unit, it's always the simple/obvious.  That said if the bike has been messed about with, or has had an alarm removed badly anything is possible.  Either will cause serious problems and if that's the case, you're going to have to trace the loom along it's length.  I've fitted an complete new loom of a few occasions due to poorly fitted/removed alarms or owners, cutting into it, or badly fitting accessories which reroute, crease, cut or damage the loom.   

I know you've said you've checked X & Y but there's really not a lot that can or does go wrong with them, not with standing the above statements. 

As mentioned, the ignition switches can often be an issue, these are known to fail/jam etc, as does the starter relay.  They're also very sensitive to battery voltage, 0.1 of an amp will make the difference. 

Look for the obvious, cut or messed about loom.

Some alarms (Datatool System 3 being the most common) aren't removed they're looped out with in it's own box. This is often poorly done, the box not being resealed and water gets in.  Another is Meta, these are cut out, often badly causing damage.   

Pull the starter relay and check to see if it's been opened, they corrode and owners open, clean and refit them, only for them to fail again later.  Check the starter and kill switches for wear/damage/corrosion any of which can/will give you a good reading but not work in practice.  Coils rarely fail, but as mentioned low circuit side can, check for broken, worn, corroded connections.  Check the instrument brinicle for it being opened, they often get opened to fix the liquid crystal display, fit blue bulbs, different clock faces. Damage can occur while it's open, and/or moisture gets in.
                 

[unfazed]

Locate the loop plugs under the seat and unplug one of them. Turn on the Ignition, press the starter button, does the engine still turn over YES/NO
If NO, put the loop plug back in and unplug the second one.
If YES continue

Turn the ignition on. Check the socket for an earth, only one of the two socket connectors should have an earth with the ignition switched on the and the side stand up. Use a Meter set to the lowest resistance scale to test it, do NOT use a test lamp as you could blow the CDI.

If there is no earth on either of the connectors in the socket then you have either a faulty ignition switch, a corroded connection somewhere or a broken wire somewhere.Earth both connector in the socket with a good earth, now turn on the ignition, engine in neutral and press the starter button and see if it fires when you spin the engine. If it does not turn over pull in the clutch and try again.
Let me know how you get on