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After emails with Clewett, looks like I will have to totally re-wire the engine plug leads and coil packs!
The crank sensor must be min 8" from any of the leads or coils or the signal is drowned out by electrical noise, so this means ripping out all the careful lead routing i did and mounting the lot where i very nearly did in the first place!
Only 2 days to do, so not too bad.

911hillclimber wrote:After emails with Clewett, looks like I will have to totally re-wire the engine plug leads and coil packs!
The crank sensor must be min 8" from any of the leads or coils or the signal is drowned out by electrical noise, so this means ripping out all the careful lead routing i did and mounting the lot where i very nearly did in the first place!
Only 2 days to do, so not too bad.

...and shielding it (electrically , not armour plating) can't be done because ..................... ?????

only asking !!

Shielded signal wire will probably fix it. I used some on the crank sensor for my mega squirt project.
A couple of metres from RS or similar only costs a few £

The sensor's lead is already shielded, two wires and a fine wire shield 'wire', the lot wrapped in a foil then the PVC outer.

This has knocked the wind from my sails atm, feel very down-hearted, but will set to tomorrow and rewire the bloody lot trying to reuse as much as I can.
I will re-locate the two coil blocks by the bell housing and hope the looms will stretch that far to the XDi position.
I've been through the learning curve and very familiar with the wiring and parts, so could be done by Sunday night.

There has been NO part of this exercise that I've enjoyed though i was pleased with my ignition cable routing, but all scrap.
Should never had started it, never ever again.

Agree about keeping the sensor wire away from HT leads but I don’t think that’s your problem.

The HT leads would have to be ‘firing’ a spark to cause the upset to the sensor signal. The engine would at least fire once before the signal is messed up but you said it is completely dead…

My advice: leave the HT leads for now. Fish out the sensor wire from the HT stuff and extend or run separate wires to the sensor away from HT.

Remember, the problem you’ve got probably isn’t the problem you think you’ve got.

What he said x2. If the coil isn’t firing, it can’t be the source of noise.

Sounds like a VR sensor, not a hall sensor (which are powered & create a square wave signal). VR sensors
Increase voltage output as the rpm increases, so are more fussy on cranking.

I have heard of ER spikes coming from alternators, causing sync loss (ferrite choke can be helpful there) and you need to be careful about your grounds (single ended at one place) to avoid ground loops. Crank sensor wires are normally grounded at one end only for that reason.

I’m guessing you have careful set the gap between the sensor & the toothed pulley? 1mm or so?

An oscilloscope is a handy tool for this game. Do you know someone with one?

Bruce M wrote:I’m guessing you have careful set the gap between the sensor & the toothed pulley? 1mm or so?

I had that problem with my Clewett set-up when the gap inexplicably closed part way through a visit to see the Sage of the Lakes.

You can trigger the sensor with a piece of metal spun in a lathe/drill then you might hear a spark without the cacophony of the engine turning.

It sounds like some folks know about these things ............. my 2p : Don't just "bull in" and rewire , you'd be kind of miffed to find yourself back at square one X days later . STOP , think ,measure, check, manage, it sensibly... find the root cause - fix that (or at least engineer a way round it for testing reasons) ...... chill , and go from there.
Right .... back out to shed in snow !!

(I could have sworn I did NOT type miffed .............. but there you are , the pc world)

Thank you all for the help.

The sensor/wheel air gap is 35 thou.
The pic below is of the installation currently. Lots of wires in one spot!
The sensor cable is shown arrowed, you all know where the senor actually is.

The 2 x coil packs have a Clewett fitted ground. I have joined these together and taken the one wire to batt neg terminal direct.

There is 12v to the coil packs and XDi unit. The 2 grounds from the XDi go to the engine ground just by the engine mount.

I (like many/most I guess) see what I expect or want to see. When fault finding something completely new like this and where I don’t find an obvious fault quickly, rather than checking directly against a wiring diagram, I draw up what’s there. I then check what I drew against the wiring diagram .

Then it’s the usual cock-ups like 180’ out

Ok:
Checked the ecu configuration is set for twin plug 911
Checked sensor connections and air gap, still at 35 thou.
Re routed the sensor cable as far from the plug leads as possible
Tried to start, nothing.

Pulled plug on #2 plug, smells of petrol, replaced.
Pulled plug #5, opposite side of engine, smells of petrol, both carbs working.

Made ground wire from plug to ground, tried to start engine NO spark on exposed #5 plug.

So, 10.45 and about to look for reason why no spark showing.

dDK'r coming over to assist!

Spent another 4 hours on the problem this morning.
Took the advice and have just re-routed the crank sensor cable away from the plug leads, and John came round to check all the wires, connections, pin locations etc with me.
We checked the plugs for working, nothing, no sparks.

Found nothing untowards, so suspect 2 things
Crank sensor faulty as the XDi light indicates
Te XDi unit is faulty.

Have asked Clewett for advice and where the sensor is sourced from.

Nothing else I can do, totally stuck.

HI
have you set the controler switchec for a 6 cylinder Duel Plug, as on page 9 of the fitting instructions??