S4 broke down and won't start

[merlin's S4]

Yeah I pulled out the starter motor. By fluke the flywheel was already in the correct position to see where the flywheel pin should be so I didn't have to rotate the engine. What was even more lucky is that the pin was sat at the bottom of the starter motor window!! I've posted some pics for your viewing pleasure.

[UrS4boy]

Comparing the photo that I posted to your's I would say two things:

1. Looks like you need a new cam cover gasket and/or half moons. That is a lot of oil leakage.
2. Your G4 pin location seems to have more corrosion where the welds were than in the photo I used. Not sure why that would be. I suppose clutch dust and moisture = nasty environment.

Clean up the G4 pin (lucky find) and the flywheel area and get a welder in there to reunite the two lost lovers.

My photo:



Your's (a bit wetter and blacker on the back of the flywheel)

[Greg_S]

Glad you found the reason for not starting.

With twoqu's comment i will try unplugging the sensor on mine and see if it then starts as that seems a sensible way to diagnose that the timing pin has come off.

It also unfortunately confirms that if the pin goes the engine starts to die immediately!
However we know from another members car that if the actual sensor is unplugged the cars still functions. Which is a bit illogical as you would have expected the no signal condition to have the same effect. Evidently, somehow the Motronic is able to tell the difference between a failed sensor and a missing pin!

Not sure if you have removed the starter yet. Perhaps the pin is laying around the bottom of the gearbox. If so you could attempt a repair. If you remove a pin from a good flywheel and cannot effect an on car repair then you would have to remove the flywheel anyway! Looks like the consolidation of an existing pin in the right position would be the best practice but more work!

[twoqu]

Greg,
You have misunderstood! I am talking about when the car is running. If you unplug the sensor the car should not start.
Another members car (HMS-S6) apparently runs better when he disconnects that sensor whilst the car is running. That seems consistant with what the documentation states about that particular sensor. The ecu somehow remembers the starting position and the car continues to run. Whereas it would appear if the pin itself goes the car starts to play up and eventually cuts out. So somehow the ecu can cope with a failed sensor but not without the pin!
Hope that clarifies things!

[UrS4boy]

Any luck with the G4 pin re-welding?

[merlin's S4]

Any luck with the G4 pin re-welding?

I've arranged to tow the S4 up to a friend of a friend this week. He's a specialist welder and reckons he can fix it so fingers crossed.

I shall report back soon.

[merlin's S4]

**UPDATE**

Well it's fixed! I towed the S4 up to the workshop on Friday afternoon. As you can imagine it was an extremely fiddly job. Firstly I pulled the starter out of the way and I also removed the metal intake cross-pipe that goes from the turbo to the intercooler underneath the engine towards the front. This gave us a bit more room to work in.

Stef from Weldspray engineering in Menheniot used a long metal strip and tacked the pin on the end so that I could hold it in position from the top of the engine bay. After several test fits and much modification of the holding strip he finally managed to tack the top of the pin into place. We removed the holding strip so we could see how it was looking. The pin appeared to have located itself back into the original position however according to the measurements shown in the following thread from urS4boy the pin was slightly too close to the outside edge of the flywheel.

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

With my permission Stef decided to grind a little off the face of the pin with a mini air grinder after welding a further small blob to the bottom of the pin. I then replaced the starter motor and intake cross-pipe. I was pretty nervous about turning the key in the ignition but I went for it and as if by magic the S4 came to life as if nothing had ever happened!

The job took about 2 hours to complete but it was well worth the effort considering the only alternative is to drop the gearbox. I think Stef would rather I had done it that way though!! Would be a lot easier to weld the pin back with the flywheel on a bench! Huge thanks to Stef for his efforts, especially as it was last thing on a Friday afternoon.

Just a further note as to the possible cause for the pin coming off. The pin looked like it had hit something to make it fall off. Of course it may have just got chewed up whilst the engine was still running. However, today I set about tightening my sump bolts as the gasket is leaking and the bolts seemed quite loose. One of the 2 fiddly bolts which attach through the holes in the gearbox bellhousing was missing. This could potentially have dropped out and sat in the bottom of the bellhousing directly where the flywheel pin comes around. There is no sign of the bolt and this may not have been the cause but it's well worth a check if you're under there!

[UrS4boy]

Good news. I hear you on the ease of re-welding the pin on the bench. However, that would open a whole while-I-am-there scenario involving the clutch, clutch slave, resurfacing the flywheel and needing a new needle bearing and flywheel bolts. Like a grand later. The laproscopic welding through the starter hole is way cheaper, even if you pay the welder for the 2 hrs it takes.

Don't open the can of worms if you already have enough bait (a good solution).