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  • engine not starting

    I'm having issues getting the engine start reliably. I have 4A0907551D ECU from UrS6 automatic converted to run prjmod firmware. Everything hardware wise is done as wiki says. Chips are fresh written, using stock AAN ABY files from Github. As i'm using this ECU in a 92 UrS4 manual, i have pin 42 grounded for it to work. So first time i tried to start engine, it didn't fire up. Switched ignition off and tried again and this time it fired up and engine worked like it should - no anomalies, noises etc. I let engine warmup for couple minutes at standstill and then turned engine off. Immediately tried to start it again and nothing, just cranking. Tried like 4-5 times again and still nothing. Exhaust smells fuel, almost seems like there is no spark. Waited for like 30-45 minutes and tried again - fired right up. Turned off and tried again - nothing. Swapped to original ECU (Stage 1+ by prj, with MAF and MPXH6400A map sensor) and it works every time i try to start it. So i'm ruling out the possibility that car side has issues.

    What am i doing wrong? Some other pin on ECU connector needs to have some sort of signal/ground because of it not being auto trans car? Or am i grounding pin 42 wrong? It is currently wired to passenger side footwell kick panel area (LHD car), where there is factory ground point. Maybe it needs to be grounded straight to ECU ground wiring? Or perhaps it needs to be switched ground? Car is stock except TFSI coils. As i understand, stock AAN ABY files should have correct dwell time already for TFSI coils (or correct enough for it to not cause issues i'm having), can somebody confirm this?

  • #2
    I can't speak for the 5 cylinder but at the V8 I can swap the ECU with the correct software without grounding anything "special".
    The difference between the manual and automatic is very small - idle valve settings for coast down and driving condition and the shifting.

    When you have already a prj stage I would insert the datalog mods in this file.

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    • #3
      Messed with it again today, no good results yet. Tested "Holding Relay" inside ECU as described somewhere in quattroworld forums and it seems to be working just fine. I got it starting like 5-6 times in a row and after that issues again. Because of that i'm ruling out possibility that my pin42 grounding is wrong. I replaced all thermo fuses above ECU with standard ones - no luck. Fuel pump relay "208" is clicking when i turn key to start engine and it looks OK inside. At some point of my testing, it actually seemed to help with starting when i removed relay, tapped it against door sill, reinstalled and tried again - had like 5-6 successful starts. But it doesn't make any sense, since original ECU starts every time, all the time. Might of been just coincidence, but i'm replacing it anyway. Took G4 and G28 sensors off, they were clean, no oil/metal shavings on them, measured resistance - all within spec. Once it starts up it runs well. Almost feels like something somewhere heats up and doesn't allow engine to start again. Another issue is when i took it for a test drive, i seem to get 0,4 bar of boost, so looks like it's in limp mode too. Might be also related to why it isn't starting? Has anybody used stock_AANABY_27c512.bin and stock_AANABY_87c257.bin files on their car successfully like they come from m232 Github without modifying them?

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      • #4
        Make a datalog of the start, may this helps.

        As I wrote, insert the datalog routine in your tuned file - I guess this would make things a lot easier.

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        • #5
          Originally posted by Acki View Post

          As I wrote, insert the datalog routine in your tuned file - I guess this would make things a lot easier.
          What do you mean by this? I have 2 ECU-s, 1st is "original" ECU with prj stage 1+ tune, and is MAF based, 2nd is the ECU i'm currently trying to get working - this one has speed density modifications done to it and a MPXH6400A MAP sensor. I'm using bin files straight from m232 Github, so they have already all the datalogging enabled?

          Datalog of the start will come as soon as i get it working. At the moment my cables and laptop doesn't want to cooperate at all in terms of getting Winlog working. VCDS works though. I have installed ross-tech VCP drivers as suggested somewhere else but still no luck, need to investigate it more.

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          • #6
            did you add the wire from the boost board to the motor chip board so the MAP signal gets to the motor chip processor? if you didnt do that it will never start. removing R660 and adding the wire is a 100% must.

            Remove resistor R660


            Remove solder from the via under "S900" chip. The via is directly under the writing "C660". Attach one end of wire through hole, the wire will go from one PCB to the other.


            Remove solder from the via directly to the right of D232 (towards D235). Attach second end of wire through hole.



            The stock startup files work perfectly, i have tested and use them on several cars with various levels of modification.
            Last edited by vwnut8392; 26th June 2018, 02:29.
            "The really good drivers got the bugs on the side windows." Walter Röhrl

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            • #7
              Thanks for chiming in. Yes, wire is in there and resistor is gone. It almost feels like this very same wire looses connection as soon as ECU warms up. Have you tested boost levels with the stock files from Github without modifying them? Are they supposed to give you 1,4-1,5 bar boost pressure ("Stage 1 tune" as stated in Github), or they are just good enough to get you started and you have to modify them on your own to get boost levels like this?

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              • #8
                Still having problems with it. Tested ECU on another stock UrS4 and exact same symptoms. Then we tested it on yet another UrS4 with chips from this car (he has a custom tune) and ECU worked like it should. So ECU is OK and chips somehow not. I wrote new boost chip and it seems to have cured the starting problem. Still not 100% sure as i have not had time to test it very much, but so far it has started every single time.
                Still the boost problem remains, i only get base pressure of ~0.4bar. Got datalogging working with cheap china KKL cable - N75 and N75_REQ stay 0 throughout the driving and pulls with WOT. MAP_REQ is fixed at 149 all the time and thats what i get with WOT. Any ideas?
                Last edited by tekstil; 10th July 2018, 17:55.

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                • #9
                  Just a shot in the dark but did you handle the chips in the non working ecu, the static from your hands can cause problems, btdt
                  1991 S2 3B Coupe, KW v1, solid sub frames, poly bushed, chipped, about 260 ish

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                  • #10
                    Originally posted by stocious View Post
                    Just a shot in the dark but did you handle the chips in the non working ecu, the static from your hands can cause problems, btdt
                    There is a slight chance yes, that this caused my weird starting issue but doesn't explain boost issue with 2 different chips. I'm not quite sure about MFTS boost cut patch, can this affect AAN engined car?
                    Surely somebody has tested files from Github and know the answers...

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                    • #11
                      I think I have a bug in the stock tune on github which is fixed in the other files...
                      Gonna check.
                      http://tuner.ee - http://www.facebook.com/tuner.ee

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                      • #12
                        Originally posted by prj View Post
                        I think I have a bug in the stock tune on github which is fixed in the other files...
                        Gonna check.
                        Any update on that?

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