According to the MJ instructions, it is essential that I get the polarity of the VR sensor correct. Fine - but I can't find anything that tells me which is VRS+ and which is VRS-. All I know is, I have a sensor plug with 0.5 metres of shielded cable attached; in that cable there are 2 wires, one of which is blue with a yellow stripe and the other is blue with a green stripe. Any clues?

I might even buy a length of cable and a new plug - they're cheap enough - but I would have NO clues then!

All help appreciated...

David

If you get the polarity wrong it will simply not spark , it will not do any damage, the easy way is to temporarily connect it and check operation .
Paul.

Strange one? I always thought that the VR sensor was working on the principle of creating an ac voltage (waveform) with a tooth missing to create the trigger point. So I'd always thought the polarity would'nt matter as long as neither of the wires were connected to chassis ground.

With a VR sensor there is usually a positive and negative going pulse on the leading and trailing edges of the tooth.
Depending on the circuitry it could either not work, as I experienced with an EDIS4, or it could result in the timing being out by approximately the tooth width.

On a Lucas RITA ignition system I used to have on a Triumph Trident reversing the polarity would change from having an advance with respect to speed to a fixed angle.

[Edited on 2/12/06 by CairB]

This is how ford wire the Crank Sensor plug.
Rescued attachment plug.jpg

That's the sort of picture I was looking for - but now I'm really confused... you talk about "sens out" & "sens earth", but the MJ wiring diagram has "+" and "-". Is "sens out" the "+" and "sens earth" the "-"?

Everything I've read about the sensor emphasised that the connection should be right way around. As everything else will be new work(MJ, wiring, EDIS & coil) I'd prefer to get as much right as possible to reduce the confusion when trying to start the car for the first time...

cheers to all,
David

[Edited on 2/12/06 by David Jenkins]

If you have a strobe light then I'd be tempted to spin the engine and check that the timing is in the right ball park.

When I first did my MSnEDIS I fitted the toothed wheel to a pillar drill, clamped the VR next to it and checked the system over with a strobe. I gained confidence when I could see the effect of adjustments on the laptop.

Cheers,

Colin

Just found this , it may help.
Paul.
Rescued attachment ford_vr_181.jpg

Magic! Ta muchly...

Sort-of says the same as Dusty's picture, but with recognisable terminology (coo - big words for a Sunday morning!)

[Edited on 3/12/06 by David Jenkins]

After all this - I took a look at the pieces of ignition kit I took off the donor car, and realised that the wires from the EDIS plug were still attached. So, looking at the MJ wiring diagram, I could have worked out which VR wire was which...
...sometimes it is useful to fully engage the brain before coming onto the forum to ask a question!

(Fortunately, the results do agree with the info given here! )

cheers,
David