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ABY starting issues - First time in 10 years

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  • ABY starting issues - First time in 10 years

    Hi guys,

    Long time since I have been on here but I need some help please.

    Now im going to start with im not a mechanic. I know basics and am more than happy to get stuck in so please forgive me if I ask stupid questions in advance.
    I do however have some very capable friends who work in garages who are helping me out but they have done some initial diagnostics and have asked me to ask some questions.

    My avant (ABY) has recently decided to not start. (Ive had the car 10+ years and never had an issue luckily). Once every now and then the car will fire and then die even if I press the accelerator. Most of the time though it just spins the engine and does nothing.

    I have plugged the car in and its giving me the obligatory G28 no signal code and once gave the G4 no signal code so I have changed the G4 and still nothing. I have checked all engine fuses and they are all ok also.

    We have used a power pin thing and checked the cam sensor and it is getting 5v to it etc when the ignition is on (is this correct?) however neither the G4 or G28 are getting any voltage to them. We are assuming this might be the problem. (Correct assumption?) If this is the problem, are the to wires powered from the ECU? Is it 1 wire that comes out the ECU and splits in the engine harness and if so where? Or is there something else we should be looking at to power these or are we totally wrong?

    Next thing, is there a common engine harness earth point somewhere I need to clean up? If so, where are the earth point locations? (See i did say there would be some stupid questions in advance. I might oddly have been able to refresh my rear subframe relatively easily but when the car is dead I am a complete numpty but dont mind giving it a look).

    Or is there something completely different that i need to point my mechanic mate to in order to look for the issue?

    Massive thank you to you all for your patience and suggestions in advance. I dont use the car often but now that I am jobless due to covid I am missing being able to get a smile on my face from it.

    Thanks all,
    Chris

  • #2
    G4 and G28 are VR sensors and do not use a power supply like the cam/sync Hall-effect sensor
    With a no-start, always check basics first - timing, compression, fuel & spark. If these are correct the engine will run.
    Unless you’ve dismantled the timing belt assembly or heard a big bang when cranking the engine you can probably rule out a timing issue. Compression also unlikely to be an issue if the engine was previously running well.
    So adequate fuel and/or spark are the first things that need to be determined.
    I would first pop the cover off the top of the fuel pump relay and manually close the contacts to test the fuel pump; pumps are a common failure.
    HTH
    Alex
    Panthero Coupé quattro 20vt
    Indigo ABY coupé
    Imola B6 S4 Avant

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    • #3
      After ten years I would change the fuel and get the injectors cleaned , they could be gummed up

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      • #4
        Fuel pump

        S2 Coupe 3B Project


        Ur quattro restoration

        S2 Avant

        Boost is the new rock and roll!
        sigpic

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        • #5
          Thanks Alex and John I hope you are right re fuel pump. I’ll see if I can get my mate to test the pump for me. Appreciate the next thing to check.

          Just to confirm the car has been in use over the last 10 years by myself... less regularly more recently but was my daily until a couple of years ago so I know the fuel is good and the injectors work lol.

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          • #6
            I read the post wrong as in not started in 10 years , lol , must be my age

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            • #7
              I have to say it could also be that your MAF is very dirty..if it starts then won't hold idle and immediately dies, that is a symptom of a dirty MAF.

              I would also try unplugging the ISV (Near the throttle body) and see if it runs then.
              1996 S2 ABY Silver

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              • #8
                Also worth cleaning the MAF plug while you are there...
                Honda CBR 1100XX Blackbird Turbo....undergoing major changes.....
                S2 Coupe... bit easier off the line...
                '03 ZX12-R daily hack.... lots of nice bolt ons...

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                • #9
                  Cheers guys, oddly cleaning the MAF plug was one of the first things I did. My friend is going to come over and test the fuel pump this weekend. He says im also not getting spark so what do I need to do for that? Im running the harness conversion for the coil packs rather than the standard set up. Alex (Error) made mine and ive never had any problems with it and it still looks good as new. (Im not at all thinking the harness has anything to do with the lack of spark). Is there something I can check with regards to the lack of spark? All the fuses are still good.

                  Thanks

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                  • #10
                    Check you haven’t lost the ground connection for the coil packs.

                    Original coils or red coilpacks?

                    The common grounding point is to the inlet manifold near the abs pump.

                    possibly the camshaft sensor has gone bad. Can be tested with an LED.

                    I would check the timing, the keyway on the bottom pulley or the cam pulley can fail and shift enough to cause a no start, the ECU needs to see the cam sensor at the right time in relation to the crankshaft sensor.
                    Last edited by newsh; 14 September 2020, 17:01.

                    S2 Coupe 3B Project


                    Ur quattro restoration

                    S2 Avant

                    Boost is the new rock and roll!
                    sigpic

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                    • #11
                      Everything your mechanic friend needs to know is here.

                      Potential solutions to why your AAN-powered UrS isn't starting
                      https://r.tapatalk.com/shareLink/top...ink_source=app

                      S2 Coupe 3B Project


                      Ur quattro restoration

                      S2 Avant

                      Boost is the new rock and roll!
                      sigpic

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                      • #12
                        Awesome, thanks John . Fingers crossed we get this sorted asap now we have some more info.

                        Oh, they are the same as the red top coils but they arent red.... (Not sure if that makes any difference?) Ill get on to checking the ground later if I get time.

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                        • #13
                          I have the TFSI coilpack conversion on my Avant, I grounded the coilpack loom to one of the cam cover bolts as it wasn’t long enough to reach to the normal ground point on the inlet manifold.

                          S2 Coupe 3B Project


                          Ur quattro restoration

                          S2 Avant

                          Boost is the new rock and roll!
                          sigpic

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                          • #14
                            Thanks again John. I'll look at that later I think just to make sure my earth is still good.

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                            • #15
                              Unfortunately it wasnt the earth for the TFSI coil harness conversion. I took it all out, cleaned it up and put it back in and its doing the same as before unfortunately. I wonder if its still giving intermittent spark? I must admit I didnt check that part....

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