No spark, no start! Please help save me some time!

[Larby]

Hi all,

I've just bought a FZ6N which doesn't start. I'm cracking on with diagnosing it, but having seen loads of awesome advice on here with other technical issues, I thought I'd ask too. Hopefully it may save some time!


Key on, dash all lights up etc as it should.
Fuel pump comes on for a bit when turned on as usual
Cranks over as usual, fuel pump runs while cranking. Pump is seeing a good 12v

No spark at all though.

Are there any specific conditions I can narrow down to, where it would crank and give fuel, but not allow spark?

I'm assuming that it'sgetting a good crank position, as the pump comes on during cranking.

Neutral light comes on, so I'm assuming the neutral switch is ok.

One coil is older, one is brand new. Primary and Secondary resistance is fine on both. Plugs are fine, I need to check the caps later to be sure, but I can't imagine all 4 would go down together.

It seemed one coil was wired back to front (red/black wire on the -ve), could anyone confirm the correct coil wiring?
I've checked the coil wiring with a voltmeter so far - I'm seeing 12v when sat with the ignition on.
I did note that one coil (the new one) seems to get very warm quite quickly, whereas the other coil (the old one) stays cold. Seems odd?

I'm going to start checking through the various sensors/swithces - kickstand, clutch, brake, neutral, tilt etc. Would any of these allow crank and fuel but not ignition though?

The starting circuit cut-off relay, does this cut the starter? Fuel? Ignition?

How about an immobiliser issue? The red light flashes when the key is off, but goes out once its turned on. Would it still crank and run the pump if there was an immobiliser issue?

Thanks in advance for any potential suggestions!
I have a copy of the manual and I'm working through things, but hoping someone may be able to narrow it down and save me some time!

Cheers, James

 

[Larby]

Slight update -

I've sussed the diagnostics procedure.
Kickstand, neutral and tilt switches all working fine.

In d:30 and d:31 the CEL flashes as it should, but still no spark from either coil.
The 1&4 coil is getting really hot, the 2&3 coil is still totally cold.

Any ideas?

Cheers

 

[Motogiro]

Welcome to our great forum!
Great description of your issue! This sounds like the switching logic on the transistors that control the coil is stuck with the one coil or the negative side of one coil (the hot one) is being held to ground. Do not turn on the ignition any more. Each coil is fed +12vdc (red with black tracer). The negative side of each coil primary winding (orange with black tracer) and (grey with black tracer) are attached to the ECU which gives timed momentary ground to each coil. The coils are meant to be triggered momentarily so the hot coil is not a good sign and may even have primary winding damage from overheating. Check your wiring and correct if needed. I would also check the ECU pins on the plug to be sure the pins are present, straight and clean.
You may have a bad ECU.

Just checked out where you live and now I want to visit!

 

[Gary in NJ]

Check the connector at the ECU for corrosion, especially if this is a bike that lives outside. Clean with contact cleaner and use some dielectric grease around the perimeter of the connector to keep water from re-entering.

 

[Larby]

Thank you both for your helpful replies!

I have already checked the coils - primary and secondary windings are within specification. One looks quite new, seemingly from the garage that had previously failed to diagnose the issue.

I've had the ECU out and it looks pretty darn good in the connector. No corrosion to note, all the pins are fine.

I did notice in the potting that just next to the connector, there seems to be a tiny slit and some 'juice' seems to have seeped out. I'm going to assume this was a component failure near this area, as it smells ofelectrical failure!

At this stage, it looks like I'm going to be into a new ECU, so I may as well see if I can get this one out of its case, remove the potting compound and hope that maybe an obvious component has failed.
If not, I'm still in for a new ECU, so little to lose I guess!

Cheers

 

[Gary in NJ]

Yeah, stuff oozing from a potted box is a sub-optimal condition. If you open it you may get lucky and find that a cap has released its magic gel, leading to a simple (and cheap) fix.

 

[Larby]

So I got the ECU apart, removed enough of the potting and found out that one of the ignition transistors is indeed total toast. Bugger.
It's so toasted that it's not even part of the board any more, there's just a charred patch where it used to be. Don't think I'll be repairing that!



Conveniently, it's the 4S8-00 ECU, which seems to be completely unobtainable, other than if I want to spend £1k+on a new one, which I dont.

So, would anyone have information on the pinouts of the ECU versions, the 4S8, 36P and 5VX models?
I'm wondering if there's a way to use one of the other part numbers, even if it means moving a few wires around on the connector?

Failing that, if anyone would have a pinout for the 4S8 ECU, I may look at putting it onto standalone management using a Microsquirt ECU, as I happen to run a performance & dyno centre. I'd probably prefer not to go to that length though!

Cheers in advance for any further help!

 

[Motogiro]

So I got the ECU apart, removed enough of the potting and found out that one of the ignition transistors is indeed total toast. Bugger.
It's so toasted that it's not even part of the board any more, there's just a charred patch where it used to be. Don't think I'll be repairing that!

View attachment 75026

Conveniently, it's the 4S8-00 ECU, which seems to be completely unobtainable, other than if I want to spend £1k+on a new one, which I dont.

So, would anyone have information on the pinouts of the ECU versions, the 4S8, 36P and 5VX models?
I'm wondering if there's a way to use one of the other part numbers, even if it means moving a few wires around on the connector?

Failing that, if anyone would have a pinout for the 4S8 ECU, I may look at putting it onto standalone management using a Microsquirt ECU, as I happen to run a performance & dyno centre. I'd probably prefer not to go to that length though!

Cheers in advance for any further help!

A little super glue and that should be good as new?

 

[Larby]

Ha ha, yep! Sadly, as happy as I am repairing electrical items, I think this is past reasonable repair.

On the bright side, the lovely guys at Motomatrix are allowing me to test a 36P ECU, with the option to return it if it doesn't work.
Pinouts are the same and it's a really basic ECU, so as long as it'll communicate correctly with my immobiliser unit, it should work!

If it does, it'll be a great option for others with the unobtainable 4S8 ECU!

I have my red key at the ready, hopefully we'll find out this coming week!