S2 ABY Wont start

[UrS4boy]

Hi all, I'm really starting to lose faith with this now, new coilpack, new hall sensor (£150 from Audi- ouch) new g40 sensors, different ecu (thanks James- havnt forgot about you) still no spark!

Umm... the Hall Sender *is* the G40 and there is only one. SOooo, I presume what you meant by "new g40 sensors" is the G4 Crank Position Sensor and the G28 engine speed sensor.

At the risk of repeating something said earlier in this thread,

1. there should be power to the white coil power connectors on the firewall when the ignition is turned on. If there isn't 12v at them, it could be an immobilizer problem or your "cooked" coils shorted out and caused the coil fuse to blow. That would result in non-starting. That fuse is the 20A fuse on the right side of the ABY fuse box (See below). While you are there, you should also check the no. 23, 24, and 25 fuses and the 27 and 28 fuses since, without them, your engine isn't going to start. (MORE below photo)



2. The ECU will not fire the fuel pump relay until it gets a good signal (and > 13 RPM) from the G28 engine speed sensor. Once it has that, it turns on the fuel pump via the fuel pump relay.

3. The ECU needs good signals from both the G40 cam position sensor and the G4 Crank position sensor. Without those, it can have power to the coils and a running fuel pump but it (the ECU) does not know where the pistons are and therefore will NOT fire either the injectors OR the coils (via the power output stages). So no start. See link:

http://forums.quattroworld.com/s4s6/msgs/20986.phtml

4. If you replaced the G4 and G28 pair, did you happen to check forthe G4 crank position pin? It has been known to fall off. With it missing, the engine will NEVER start, ever again, until you replace it properly (see link below)

http://forums.quattroworld.com/s4s6/msgs/51259.phtml

[Biggss2]

Hi mate thanks for your detailed reply

I will recheck fuses checked initially but haven't checked since it gave up on me 2nd time, when lower 2 sensors were replaced the pin was still there an is visible

Sorry with regards to the sensors I have replaced the one behind the top crank pulley (cps) and the other double one by the flywheel/pin

I'm going to check the 20amp fuse as soon as I get home..

Will report back

Thanks for your help and concern, i genuinely appreciate it

[Biggss2]

20 amp fuse it shot!

Replaced and car started 1st time!

Urs4boy can't thank you enough mate!

I really appreciate your help guys, audrelious who was coming up to have a look at it on Saturday, what a scholar and a gentleman. Newsh ur kind help, James ur help was very much appreciated as was yours kulster and everyone else who has contributed in the dilemma iv had with this car past month

Now the only thing im wondering is a) why did the coil pack go, was the cam sensor a good idea to change, spark was weak initially to begin with

B) what can I investigate to prevent the re occurrence of the problem

Again all can't thank you enough for your help and support was nearly giving up on this!

[Biggss2]

I'm going to frame this bloody fuse it's Been the bane of my life

[Biggss2]

Hi all..

Cars running I had it on vagcom (vag106) with an adaptor- works a treat..

It has bought up the following 1262 solenoid valve for boost pressure control (n75) 31-00 open or ground to short

And 0514 ignition point sensor (g4) 03-00 no signal

Faults cleared ignition off, back on and faults re appeared I'm wondering if these two faults are interlinked and which one would be best to look at first?!

Thanks to jonnybravo who has advised the n75 valve is behind drivers side light!

Any ideas, advice, suggestions would be more than helpful.

Thank you!

[UrS4boy]

20 amp fuse it shot! Replaced and car started 1st time!
Urs4boy can't thank you enough mate!

You're welcome. Now which 20 amp fuse was it? The No. 27 or the No. 32 (I think it must have been the 32).

If it was the the No. 32, it likely is the result of a dead short between one of coil power wires where it enters the coil pack "20v Turbo" cover. Remove the coil pack cover and examine the wires. I suspect you will find insulation flaking off and exposed wires. If so, either replace the wires (cut, strip, crimp/solder and heat shrink (tubing on before you make the connection)) or simply wrap the wires with electricians tape in the short (bad pun) run.

[UrS4boy]

It has bought up the following 1262 solenoid valve for boost pressure control (n75) 31-00 open or ground to short And 0514 ignition point sensor (g4) 03-00 no signal. Faults cleared ignition off, back on and faults re appeared I'm wondering if these two faults are interlinked and which one would be best to look at first?!

Well in terms of making sure the engine runs, the G4 crank position sensor is the most important. The strange thing is IF there was no G4 signal, the engine should not start or run. But yet you say it is. Hmm...

Here is some G4 info:

http://forums.quattroworld.com/s4s6/msgs/20986.phtml

As for the N75, it might be a bad connection. Here is some N75 info, including a link to check the communication between the ECU and the N75:

http://forums.quattroworld.com/s4s6/msgs/20987.phtml

[Biggss2]

Hi urs4boy

It was indeed number 32.. The brown wire on the last coilpack was very exposed before I dismantled it I thought it was an aftermarket earth wire someone had just slapped on! I got a new set of coilpacks with a nice brown wire on them so hopefully that would have eradicated that problem!

As for the g4 i think it might be a ghost fault, however I cleared it, and put ignition on only for it to come back on, admittedly the key wasn't out the ignition long before I put it back in so will try again tomorrow with a bit of an interval in between clearing faults!

Even with the fault code it starts up a treat :s I'm going to swap the plugs around on the sensors just in case I got them the wrong way around!

I'm going to have a look at the n75 link now!

Thanks for your kind help

Hoping to get this back on the road and boosting soon

[UrS4boy]

Well the exposed (uninsulated) wire was likely/hopefully the cause of the shorting of the power to the coils via your fuse No. 32.

As for the G4 and G28, the G4 connector plugs are black and the G28 connector plugs are grey. Don't swap them without checking. Somebody might have swapped the sensors at the bell housing (The sensors are the same electrically). The sensor that is closes to the front of the engine is the crank position sensor and should be connected to the black firewall connector harness plug (even if the sensor plug is grey). The sensor that is closest to the firewall/ transmission is the engine speed sensor and should be connected to grey firewall harness connector plug (even if it is black). Normally black is closest to the front of the engine and grey closest to the transmission.

[Biggss2]

Hi

Yes we did change them at the bell housing! So you are saying they are the same, I could swear that one looked a little longer (cylinder shape metal bar) than the other, I could be wrong will definitely check the plugs, after iv vagcomed it again!

Thanks for your help it has proved priceless..

[Biggss2]

Hi all

Upon further investigation, the plug on the n75 had come loose and was disconnected, vag lead went pop so can't vagcom it to rule out this problem (1thing after another arrrrgghh)

The only problem (fingers crossed) I'm left with is the radiator fan, initially when battery was on car the fan would run regardless of ignition, keys out fan running.

So I changed the brown relay by drivers footwell, ok so now the fan doesn't run automatically, however only runs for like 15seconds when the car reaches 90degrees goes off temp goes to middle- no fan cutting in?! Bear in
Mind this Is on standstill, will the fan run more when I drive the car.. I don't want to cook the coilpack, definitely don't want to cook the engine :s

Thanks in advance

[UrS4boy]

Upon further investigation, the plug on the n75 had come loose and was disconnected, vag lead went pop so can't vagcom it to rule out this problem (1thing after another arrrrgghh). The only problem (fingers crossed) I'm left with is the radiator fan, initially when battery was on car the fan would run regardless of ignition, keys out fan running. So I changed the brown relay by drivers footwell, ok so now the fan doesn't run automatically,

With the N75 connected again, you should now be getting full boost (disconnected = mechanical boost only).

The brown (324?) relay is the after-run pump relay that runs the after-run pump and the rad fan after the engine has been shut down hot. See: http://forums.quattroworld.com/s4s6/msgs/21503.phtml for more info.

[Biggss2]

The 20v turbo cover is getting real hot too, just like the last one before it got cooked, have I got the plugs wrong, I've swapped them around but car still starts as it would if they were incorrectly plugged to start off with

Just as I get over a hurdle, I take a fall with this

Any help is appreciated.. Thank you

[Jonnybravo]

The top of those engines get extremely hot, I would doubt that is anything unusual unless its warmer over one particular coilpack.

[UrS4boy]

The 20v turbo cover is getting real hot too, just like the last one before it got cooked, have I got the plugs wrong, I've swapped them around but car still starts as it would if they were incorrectly plugged to start off with
Any help is appreciated.. Thank you

The 20vTurbo cover always gets hot (enough to burn you). Not to worry.

As for the G4 and G28 plugs, go back to my previous post regarding location on the flywheel bell housing and make sure the front sender (now the G4) is connected to the black firewall connector and the rear sender (now the G28) is connected to the grey firewall connector. In theory this should be black to black and grey to grey but if somebody messed with them at the flywheel the could be messed up.