Non Starter - Troubleshooting Help Required!

[Si Blythe]

Guys has you may know, my S2 decided it didn't want to start after I parked her up after changing the heater matrix. I had diagnosed a dropped pin from the flywheel however, much to my embarassment, I have discovered the pin is still there! I did a sanity check for my piece of mind and I can actually see it. I am now thinking cam sensor but my gut says the ignition module on the bulkhead. Anyway as always your advice is most welcome and needed please. I am wondering if there is anything in the dash that may have come off that would stop her starting?

Cheers,

Simon

[newsh]

Have you checked the fuel pump?

[Acidburn]

from what i'm aware the ignition module on the dash both would have to pack up as if one goes off then it would run/sound like a subaru on 4 cylinders

[Si Blythe]

When I did the relay check it fired up the fuel pump however it doesn't energize on with the key in position 1 which I thought it should.

[UrS4boy]

I think you need to get some definitions fixed before you start (and we try to help you):

"dash" = interior, the mostly plastic part from the base of the winshield rearward that holds the instrument cluster, glove box, etc.

firewall = metal part that protects the interior from noise and damage, e.g. fire.

The ignition modules = power output stages(POSs) mounted on the firewall. Lots of good reading here:

http://forums.quattroworld.com/s4s6/msgs/15284.phtml

POSs rarely totally fail. Typically they lose one channel = one cylinder no longer gets a strong (or any spark) = missing WOT and then, after total channel failure, missing at idle. Even a failed POS channel will not stop the engine from starting.

You have to start at the beginning and confirm that the fuel pump is working, that you have spark (or not). Paul Nugent's diagnostic list is a good place to start.

Or this:

http://forums.quattroworld.com/s4s6/msgs/22611.phtml

[Si Blythe]

Ok - I understand the dash to be big plastic piece below the windscreen. I removed this to change the matrix.

The firewall/bulkhead is the separation between the interior of the car and the engine bay. The POS's were removed and disconnected to allow access to the matrix pipework and retaining bolts.

An auto electrician diagnosed a faulty crank and or cam sensor (I think no g28 or 34 signal) he has stated the ECU isn't reciving the signal and subsequently is not sparking.

I removed the top off of the fuel pump relay and held the contacts together - to my ear this energized the fuel pump.

After fitting the heater matrix I started the car several times without incident -I drove the car home afterwards too. The car failed to start the following morning.

[UrS4boy]

Hmmm...didn't know that you *had* to remove the dash on a B3/B4 to change the heater core/matrix. On the C4s, it is NOT necessary to remove the dash to do make this change.

Back to the non-start: No starting in a morning after being fine the night before is typically one of two things: Fuel pump failure or cam position sensor (G40) failure.

Here is some C4 fuel pump failure diagnostic info that you might be able to adapt to assess your fuel pump situation (follow the hyperlinks inside too):

http://forums.quattroworld.com/s4s6/msgs/22623.phtml

Here is some G40 cam shaft position info that might help (follow the hyperlinks inside too):

http://forums.quattroworld.com/s4s6/msgs/22580.phtml

[Si Blythe]

Thanks urS4boy I appreciate your help.

[newsh]

Yep heater matrix is a dash-out job for us S2 guys

[newsh]

You could try running water over the cam position sender, this sometimes works.

The other thing, I can't remember if you have an aftermarket alarm on the car?

[orangepeel]

just on the off chance have you checked all off the fuses

[Gazjen]

The fuel pump relay shouldn't pull in on ignition only when cranking

Does it pull in when cranking?

Is it sparking?

[UrS4boy]

The fuel pump relay shouldn't pull in on ignition only when cranking

I think Paul N and others have established that the Fuel Pump relay isdefinitely NOT activated by just turning the ignition to "on". However, once the ignition is turned to "start" and the cranking speed gets the engine to greater than 13 RPM (VAG info said 23 RPM but Paul N has bench tested this to 13+ RPM), as measured by the G28 engine speed sensor, THEN the ECU will trigger the FP relay. This then provides more power to injectors, etc. than just the Holding Relay did. However, the ECU will not actually trigger the injectors or the spark unless it has good signals from both the G4 crank position sender AND the G40 cam position sender.

J17 FP relay (for C4 UrS) info:

http://forums.quattroworld.com/s4s6/msgs/22583.phtml

Holding Relay info:

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

Fuel Injector info:

http://forums.quattroworld.com/s4s6/msgs/20441.phtml

G4 and G28 info:

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

[Fat Audi 80]

My money in on Cam Pos Sensor G40. Agree with Newsh, pour some water down the back of the cambelt as your first "try".

If you have driven the car after the Heater Matrix swap it sounds like you have put it all back together correctly and this problem is a coincidence...

HTH

Cheers,

Steve

[Si Blythe]

No joy with the water test. I have taken the cap off of the fuel pump relay - it doesn't energize! If I squeeze the contacts together it does fire up the pump, maybe the relay is caput?