AAN no fuel or spark???

[Alan]

Having recently changed the timing belt and water pump on my ur S6,
the car has decided to stop working. It was running perfectly after I changed the belts, and I also flushed the cooling system and topped up with new coolant.
I have no fuel pressure or spark, I have closed and opened the car with both keys thinking the immobiliser may be at fault but nothing.
Any ideas?

[Jonnybravo]

Crank sensor possibly, that triggers the ignition and fuel pump on a Vauxhall which runs a similar Motronic ecu.

There is probably a 3 pin connector or similar you may have disconnected whilst working in that area, someone on here will know that for sure

[Alan]

Could water damage the sensor?

[Jonnybravo]

As the sensor is sealed I'd say no but it could get into a connector which could cause a problem. I'm not familiar with the wiring or sensor location but that is where I would start looking.

[UrS4boy]

Crank sensor possibly, that triggers the ignition and fuel pump on a Vauxhall which runs a similar Motronic ecu. There is probably a 3 pin connector or similar you may have disconnected whilst working in that area, someone on here will know that for sure

Possibly. But what is more likely is the cam position sensor behind the exhaust cam sprocket. The connector (3 pin) is near the front end of the fuel rail. Might have come undone. If the Motronic ECU does not get a cam position signal during start up, it does not fire the fuel pump relay (so no fuel). The fuel pump relay also controls a bunch of other stuff including power to the fuel injectors (again, no fuel).

Try these for help:

http://forums.audiworld.com/showthread.php?p=18856859

http://forums.audiworld.com/showthread.php?p=18872779

http://forums.audiworld.com/showthread.php?p=18824663

http://forums.audiworld.com/showthread.php?p=18849794

Hope some of that helps.

[Alan]

Thanks for the info.
Is there an easy to test the sensors (i.e. resistance) without removing them?

[UrS4boy]

Thanks for the info. Is there an easy to test the sensors (i.e. resistance) without removing them?

I am sure that Paul N. will correct me if I go wrong here but...

The cam position sensor is a "Hall effect" sensor that, in this case, takes voltage to ground as the cam sprocket rotates. SO...I think if you place a digital multimeter on 0-12V in line with the ground side of the two wire connector (you'll have to jumper the 12 V feed line to the cam sensor (at the fuel rail connector location)), you should probably see the voltage go from 0 to 5 to 0 to 5 as you crank the engine (two person job). Having an oscilliscope would be handy here.

More Hall effect info from Wikipedia:

"Commonly used in distributors for ignition timing (and in some types of crank and camshaft position sensors for injection pulse timing, speed sensing, etc.) the Hall effect sensor is used as a direct replacement for the mechanical breaker points used in earlier automotive applications. Its use as an ignition timing device in various distributor types is as follows. A stationary permanent magnet and semiconductor Hall effect chip are mounted next to each other separated by an air gap, forming the Hall effect sensor. A metal rotor consisting of windows and tabs is mounted to a shaft and arranged so that during shaft rotation, the windows and tabs pass through the air gap between the permanent magnet and semiconductor Hall chip. This effectively shields and exposes the Hall chip to the permanent magnet's field respective to whether a tab or window is passing though the Hall sensor. For ignition timing purposes, the metal rotor will have a number of equal-sized tabs and windows matching the number of engine cylinders. This produces a uniform square wave output since the on/off (shielding and exposure) time is equal. This signal is used by the engine computer or ECU to control ignition timing. It is worth noting that many automotive Hall effect sensors have a built-in internal NPN transistor with an open collector and grounded emitter, meaning that rather than a voltage being produced at the Hall sensor signal output wire, the transistor is turned on providing a circuit to ground though the signal output wire."

[Alan]

I decided to get an engineer friend of mine to look at the pickups and hall sender, and it would appear they are all functioning OK.
He said there is no signal coming from the ECU to the Hall sender (camshaft) which points to either ECU problems or the immobiliser has stopped it from working.
Is there an easy way to test the ECU or is there a self test for the S6?
Alan.

[UrS4boy]

He said there is no signal coming from the ECU to the Hall sender (camshaft) which points to either ECU problems or the immobiliser has stopped it from working. Is there an easy way to test the ECU or is there a self test for the S6?
Alan.

If you haven't already, you should check for 5 V power from the ECU via the red wire from pin 12/55 on the ECU connector to the Hall sender.

Have a look at this (also pin 8/55):

http://forums.audiworld.com/showthread.php?p=18872781

[Alan]

We did check for power from the ECU to that connector but there is none.
Alan.

[prosty]

Checked the normal engine fuses?

[Alan]

Yes, we checked all the fuses, all ok...

[Alan]

Not having any luck here at all.
Is there any way of checking definitively if the immobiliser is preventing the ecu from turning on?
Thanks again,
Alan.

[S2central.net]

Yes - you need VAGCOM though... does this car have the factory fitted immo - with little car/key logo in the instrument cluster ?

[UrS4boy]

Not having any luck here at all.Alan.

Have you tested the fuel pump by supplying 12V + power to it directly through the downstream side of the Fuel Pump fuse holder (fuse out)? I know that doesn't solve your spark problem but it would, at least, rule out a dead fuel pump.

Here is a FP testing procedure I wrote for the C4 AAN people:

http://www.elektro.com/~audi/fuelpump/index2.html

By the way, my money is on the cam position sensor. Either the sensor itself or the connection between the harness and the cam sensor. That connector tends to crumble with age. You *might* want to check that all three pins are fully engaged.