My silver RS2 Project

[K Simmonds]

The vacuum pump is linked to the factory alarm/immobiliser so that could well be the problem.

[Tractor Dave]

I'm not convinced its the issue. Apparently the car was running before it was stripped and these wires look like they were cut a long time ago. Tape used to insulate looks the same as the alarm stuff.

[hashluck]

We had the same problem with a Coupe. The central-locklng pump in the boot had stopped working and my business partner disconnected it without me knowing whilst we sourced a replacement. Next time we went to start the car, nothing doing. It took a while for me to make the connection and tracing circuit diagrams! Plugged it back in and hey presto!

[Tractor Dave]

Thanks guys. Quick update. Tried with wires connected and made no difference. I have tried testing g4 crank position sensor with led but got nothing. I dont think the voltage will be sufficient to light it up though. Hopefully will get the battery for my oscilloscope today and i can test properly.

[johne]

The vacuum pump is linked to the factory alarm/immobiliser so that could well be the problem.

The vacuum pump for the locking is in the same box as the alarm system but there's no link to the factory immobiliser, that's entirely separate.

I've had a look through the wiring diagrams for the factory alarm (V94) and I can't see any way that the alarm unit can get its oar into the starting of the car. There is the link to the radio but even that can't do any more than set the alarm off ???

That's true for a S2 but having done more digging for Dave the situation is more complicated on a RS2 which I'm investigating.

[johne]

The crank position sensor is just a coil of wire around a soft iron core so all it can do is generate a voltage pulse which you'll need your 'scope to see. It's not like G40 which is a Hall sensor but the same as the ABS wheel sensors for this generation of cars.

[John.]

So if it's not a hall sensor then it's an inductive pulse ?

[K Simmonds]

The vacuum pump for the locking is in the same box as the alarm system but there's no link to the factory immobiliser, that's entirely separate.

I've had a look through the wiring diagrams for the factory alarm (V94) and I can't see any way that the alarm unit can get its oar into the starting of the car. There is the link to the radio but even that can't do any more than set the alarm off ???

Thank you for that info Johne, as it happens that's very useful to me.

[Tractor Dave]

A little update
A set up my scope



I got a good wave from the speed sensor but not so good from the crank position sensor




Not so easy to take pics.

So while waiting for the new sensor I thought I would test a few basics at the ecu. Then I noticed something.




All the brown and yellow wires have been cut and join these black wires. This doesn't look oe to me?


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[johne]

The speed sensor will give many pulses per revolution of the engine (I can't remember how many teeth there are on the flywheel ring gear) but the position sensor only 1 which alone will make it hard to see. The two sensors are identical so you can swap them over to check them out.

There are a couple of legitimate crimps in the engine wiring loom. Have you got a copy off S2central or do I need to send you one?

[Tractor Dave]

As I thought. The loom disappears behind the air box and i cant see what bodgery continues. This wasn't part of the alarm i removed. There must be another box of tricks hidden behind the airbox

[Tractor Dave]

Looking at S2 central schematics, these are the ecu earths.

[Tractor Dave]

Anyone de pinned the ecu connections before? Are they junior power time?

[johne]

That crimp is OE, it's the major grounding point (138) in the ECU wiring loom with a bunch of brown/yellow and black wires going to it. Would be worth checking though that it is still connected to ground.

For future reference:

Injector feeds from ECU:

Cyl 1: br/sw
Cyl 2: br/bl
Cyl 3: bg/gn
Cyl 4: br/ws
Cyl 5: br/ro

The returns are all bl/sw which go to a crimp in the loom and then continue as 1 bl/sw to a relay switched battery feed via fuse S28 and also to the ecu itself on pin 37.

[Tractor Dave]

Ok, thanks. Also found this slightly further up.



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