Audi s2 3b won't start PLEASE HELP

[Stealthacq]

Well the ecu came back today as been 100% fine so there carnt be any bad shorts to impact the ecu.
Back to the drawing boards with pinouts!!
Can anyone confirm the 47/48 and 49 pinouts for the 3b are correct the
47 speed sensor blue contact 2
48 speed sensor gray ciontact 1, crank sensor lilac contact 2
49 speed sensor red contact 1

Prev: it was:

47 gray speed sensor
48 speed sensor and crank ref red and blue
49 lilac crank sensor
The original red and wires off pin 48 do Not look like they have been altered so am I looking a t the drawings wrong!

I was getting a speed sensor code but if the sensors signal cables were wrong this would explain the crank not showing up?!?

[twoqu]

I'll add a not too good pic. The connectors are positioned in the pic and measurements are from left to right, so 1 is on the left!

Black connector.
Pin 1 to ecu pin 48 (?)
Pin 2 to ecu pin 49 (Red?)
Pin 3 to ecu pin 19. (Black)

Grey connector
Pin 1 to ecu pin 48 (Lilac with brown tracer?)
Pin 2 to ecu pin 47 (Blue?)
Pin 3 to ecu pin 19. (Black)

Its very difficult to see the colours so all I can say is that the wires have at least that colour on them although they may be trace.

[twoqu]

Of course the colour of the wires may vary from model year to year but the pins assignments shouldn't.

[Stealthacq]

Well I have correctly wired the crank and speed sensor tonight and still no start
I checked speed signal and it was good like an AC wave form
Checked the crank sensor and its hard to see but it looks hit and miss
Checked the 5v pin 8 g40 cam sensor again it is hit and miss
I have a spark all the time
I notice if the signals are good on the key it will inject fuel but because it's not consistent it stops but yes it still sparks but it is on distributor so this would make sense!
I think am going to look at replacing the hall sensor in the distributor first!
Am soon close I can feel it haha
Thanks for the help and time I really appreciate it

[tartanmotorsport]

Hi,

Sorry if I'm misunderstanding this post or it has been mentioned before. I'm at work so I don't have time to read every post. I had a similar problem once before, it turns out the crank pulley keyway sheared moving the crank pulley. I was checking timing with the crank pulley and not the window on the gearbox (lesson learnt)

The only way I caught it was with using a dual channel labscope. Cam and Crank correlation were out a few degrees.

Again if I'm misunderstanding discard all this dribble.

Back to work .

Cheers

[Stealthacq]

Hiya I have ensured it was timed up with the fly window as the belt wasn't so tight so I just double checked.
It is all bang on and does try starting.
This has to be a signal issue.
Am going to hotel re the g40 tomorrow just to illuminate any wiring but if no go change the dizzy as I have a spare 3b dizzy. The current 7a dizzy that's in did come off a runnibg car
Cheers for the reply

[twoqu]

It would have been useful to use the scope to determine the G4/G40sync and rule that out.
Having said that its happy enough to provide sparks, which leaves us with the injectors.
What is the p/n of the injectors?
Again it would be useful to pull codes after any attempt to start it just in case the ecu is clever enough to pick it up.
It also allows you to generate faults and see what the consequences are. For example, if you disconected the G4 and you get a code and no sparks that would support sync with G40. You could have also used the output tests to see whether the injectors operated under those conditions although that would not necessarily rule them out of the equation. Another advantage would be that they dribble a bit of fuel into the engine which may be enough to fire it up.
To a certain extent we are back where we started. As above you may have to do a precautionary cambelt change to ensure there is no issue with either pulley.

[Stealthacq]

Yes if they did dribble a but of fuel this would be right.
But the noide lamp only flashes the once on occasions. And this is when it tries to start.
So it must be a signal issue.
It's got to be this cam or crank signal.
I do have the snap on kit to try to do the output tests as am sure this kit does this.
That would rule out shorts in the injector grounds.
I did quite a bit ago put fuel down the bores and it did fire up for a second.

[twoqu]

I was wondering if this vehicle was ever fitted with an aftermarket ecu previously. Sometimes that means the G4/G28 are rewired. It might also mean that other components might have been changed such as the injectors. It was also supplied with that scrapyard ecu rather than the original which either means the original was sold or suspected of being faulty.
Anyway, check the p/n of the injectors just to double check we are dealing with stock stuff!

[Stealthacq]

The ecu does not looked like its been spliced only for an immobiliser. But that has been moved before.

[twoqu]

It wouldn't as the aftermarket ecu pugs into the stock loom but you do on say a VEMS have to alter some of the pins assignments, particularly the sensors I believe. If the wiring was not altered then its not a concern.
As for an immo. If its been removed and not reinstated we would be expecting to see something missing in terms of power or signal I guess.
Reading between the lines somewhat it seems that if you get sparks you get the injectors so presumably they use the same signals. You have power so that leaves the ecu return through ground which seems to be intact.
If for example the injectors had been changed for low impedence ones, I think the ecu would not be able to drive them. Obviously if they are stock then that would not be the case. Unless they are faulty of course.
Guess you could use the scope to see if the injector is being pulsed rather than the test light.
If we are correct it seems to be pointing to the injectors so we need to prove they are capable of functioning and are receiving the signals.

[Stealthacq]

When I manually ground the injectors they do open and you can hear them. Al scope them out. Al see if I can get my drop box back on and send some images. Cheers

[Stealthacq]

Right I think I have found the problem!
The injectors 12v supply reduces dramatically when cranking so there's ether a short or something.
This makes sense why they pulse on the key and go out.
Is it the s27 fuse that supplies the injectors?
But it does have 13v on ignition on
Just when I start it reduces to nothing really!!
Getting closer!!!

[Stealthacq]

Is it bad if I wire 12v from the battery to the injectors? Obviously disconnect the shirt feed??

[twoqu]

Thats funny as I was just looking at the factory testing method again especially the relationship between the fuel pump relay and the injector fuse. Basically the fpr energises both the fuel pump and the fuel injectors. It has two set of contacts. Better to read the workshop manual that Mike linked to as it explains what contact connects to the fuse.
I have S28 but just trace it back from one of the injector connectors.