Another non-start!!

[Donnie]

That was my thinking too, so I checked the joined up moter/moteur fuse holders for voltage, with the meter grounded on the camcover and the test probe in the fuse sockets one by one, 0v at any point - WTF!!!!

There is electricity at other systems eg. windows & courtesy lights etc.

Its properly dark now, mission aborted till morning - battery on charger.

[twoqu]

So are you now saying that there is NO power on the fuses under the Moteur cover with the ign on?
You will see from the link I provided the importance of those.
That might indicate the fuel pump relay is not switching through terminal 87a I think.

[twoqu]

Fuse S27 should be permantently live as its for the Motronic memory pin 18. Fuse S28 is tripped via the fuel pump relay. Fuse S32 not only feeds the coils but is an ign 12V feed into pin 27 on the ecu.

Would be better to earth off the body rather than the engine.

[UrS4boy]

Nah, Zero Ohms = short circuit, ie not broken!

Reading your response, I was confused. Hmmm... so I went down to the basement. Got my analogue multimeter out, set it to Ohms and touched the probes together. The needle swung quickly clockwise from left to right, all the way up to....

Wait for it....

ZERO.

It starts at infinity with the probes not on anything and then goes down from there, to zero when there is a complete circuit. DUH.



I guess I've only been using it as a continuity meter (i.e. needle swings to right if circuit is good) and never really looked at the reverse scale that it runs on for ohms.

My bad.

[Donnie]

Correct, no juice to either of these fuses with the ignition switch on - fuel pump relay is operating correctly ie. its pulls over and runs the pump during cranking.

My brain hurts

Think i'll go and buy a renault clio diesel

[twoqu]

Yep but the fuel pump relay also switches power to other fuses including S28 which feeds the injectors and by the look of it ecu pin 37. This is off the bottom of the fusebox by a designated pin 87a!
Then there is S27 which is also fed from the bottom of the fusebox on one of the 30 terminals which are battery live. That goes directly from the fusebox through S27 to the ecu pin 18.
Then fuse S32 is an ign switched feed to the coils and the ecu pin 27.
So if you have no power on any of those then the ecu has no power. Whilst they may be some ignition switched problem, it shouldn't effect the battery fed 30 terminals which are permentantly live!
Tis odd!

[UrS4boy]

Yep but the fuel pump relay also switches power to other fuses including S28 which feeds the injectors and by the look of it ecu pin 37. This is off the bottom of the fusebox by a designated pin 87a! Then there is S27 which is also fed from the bottom of the fusebox on one of the 30 terminals which are battery live. That goes directly from the fusebox through S27 to the ecu pin 18. Then fuse S32 is an ign switched feed to the coils and the ecu pin 27. So if you have no power on any of those then the ecu has no power. Whilst they may be some ignition switched problem, it shouldn't effect the battery fed 30 terminals which are permentantly live!
Tis odd!

The fuse that feeds the T55/18 power to the ECU also feeds the Holding relay and without the Holding relay working, the engine will not start. Here is some info that might help:

Holding Relay info:

http://forums.quattroworld.com/s4s6/msgs/102009.phtml

Motronic Info for AAN (similar to ABY and ADU) (Fuse numbers different for S2/RS2)

http://forums.quattroworld.com/s4s6/msgs/21009.phtml

[Donnie]

I AM THE MAN!!!!

It was corrosion on the terminals of the thick red wires - I presume this is the supply(s) to the main fuse box.

I thought I'd have one more look last night, cos it was dark I noticed a slight spark under the fuses - stripped back the (vast amounts of) wiring and attacked with emery cloth an electrical cleaner.

After a marathon re-assembly session la s2 est fully functional once more.

Thanks everybody for the help - mucho gracias.
:mischeif:

[prj]

Congratulations

[twoqu]

Good news!
No power in, no power out!
For the record pin 37 is indeed a feed out from the ecu to the injectors and other components including fuel pump relay. As Dave has said this is switched by the holding relay in the ecu from input at pin 18 to output at pin 37.
The ecu gets its power to pin 18 from the fusebox T30 (bat 12V) and pin 27 from the S32 fuse which is an ign switched 12V source.