Problem with "short-to-ground" VAG-COM

[iqbad]

Hello, I have an Audi A3 1996 with the 1.8L non-turbo engine. I have a problem that the engine just dies sinstantly during driving. it is most of the times possible to start it again after a short while, but it can die again at any time.

The following fault codes are registered:
01249 - Fuel injector for cylinder 1(N30)
29-10 -Short to ground - intermittent

Similar fault codes exist for the other cylinders (I have a common error for all injectors).

The car is equipeed with Motronic M3.8 if I understand correctly.

I cannot find any electrical wiring diagram for the engine or Motronic 3.8! Haynes has nothing about any engine, and i have not been able to find schematics online. My understanding of short to ground is that the ECU does not get sufficent current through the injectrors when it grounds the injector, this could maybe be from high resistance on the supply, or high reistance down to ground after the ECU

Questions:
1. Has someone had these fault codes before? how did you solve the problem?
2. does anyone have a circuit diagram for this engine, or maybe to a 1.8T that should be similar?
3. Where is the ground point to the ECU located?
4. I have googled that the fuel relay might have something to do with such codes, does anyone know anything more about that?


Best regards Eric

 

[iqbad]

I have now checked all ground points that I could find under the hood and made sure they have proper contact to ground. I have also taken the fuel pump relay apart and sand-papered the contacts for improved connections. The failures are unfortunately still there with frequent stalls of the engine.

Several more "short-to-ground" codes are also generated, for the camshaft position sensor and the MAF-sensor. These must have some common points that should be checked.

Are you guys sure that no one has some electric drawings for an A3 (or A4 for that matter) engine with motronic?

 

[Ian2012]

Some of the earth points are well hidden on the a3 have look under the battery if you haven't already, short to ground doesn't always mean its an earth problem have you cleaned the fuses on top of the battery if you have them depending on model

 

[iqbad]

Some of the earth points are well hidden on the a3 have look under the battery if you haven't already, short to ground doesn't always mean its an earth problem have you cleaned the fuses on top of the battery if you have them depending on model

Thanks for your reply Ian. I have checked the connection for the fuses on top of the battery and they look fine, I have also measured the resistance over them and no remarks there. Do you know where the earth points for the injectors are placed? Is it one of the points just next to the battery (left hand side of car, close to the left headlight?) I am thinking about shortening them 10cm and replacing the ends with new wires since the cores in the cables look corroded in the end.

I have yesterday inspected the ECU connections and they alos look fine. I also removed pittings on the fuel pump relay contacts but the problem is still there. I have now ordered a new fuel pump relay and will try with that.

 

[iqbad]

I have now replaced the fuel pump relay and also made new ground connections to all ground points I could find under the hood.

The ground connections were located:
3 x right hand side of the battery (when standing in front of the car)
1 x under the battery holder
1 x on engine block front side
1 x on the wall just in front of the ECU

I now need to drive the car for a longer trip to see if the problem is solved or not.