Wiring up Idle Control Valve

Discussion in 'K-Jetronic OEM injection' started by Breadfan83, Jun 25, 2019.

  1. Andrew Powell New Member

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    OK ECU Bosch 0261200298 digifant 2 037906022N engine code 026103373AA 2pin idle/wot switches I think if that's the ones on the throttle body
     
  2. rubjonny

    rubjonny Administrator Staff Member Admin

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    ok so its running a mk2 digifant ecu then, and if it has a separate idle and wot switch its got the right mk2 head/inlet/throttle on it as well. the airflow meter is worth a look, the engine wont run right if its a little dicky. does sound like yopu're loosing spark when hot though, have a look at the ignition amp make sure its in a relatively cool place wjhere it can get airflow and its attached to a heat sink. mk2 ones are glued tyo an alloy base but mk1 era the heatsink is seperate and may have been forgotten during swap

    theres no diagnostics on the mk2 ecu so nothing you can do there
     
  3. Andrew Powell New Member

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    Thanks for the tips the airflow meter has been checked and set up to parameters so I'll look are try non return valve on the fuel pump side as cheap option and the ignition amp is just fixed to the engine bay up high and not well vented so certainly worth checking. Out of interest do the ignition amps fade over time and get worse with heat if they get too hot as this might explain why cold start is perfect hot is not Before I ask one to many dumb questions do you know anyone in the sw area who may be able to help as I've reached the end of my limited knowledge. Thanks again the tips and advice on here is a wonderful resource
     
  4. Andrew Powell New Member

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  5. rubjonny

    rubjonny Administrator Staff Member Admin

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    If you suspect the fuel pump non-return you can easily test this with a pressure gauge, check the residual pressure as mentioned. If it drops too fast try again but clamp the feed line to rail after switch off and see if it stays up. if it still goes down clamp return as mentioned in the guide, if that helps then its fpr or leaky injectors

    this is the mk2 type ignition module with integrated heat sink:
    https://www.ebay.co.uk/itm/303602077346

    they dont like being hot so if yours is mk1 style without its heatsink and its mounted in a hot place that wont help, mk1/2 they're mounted in the scuttle so lots of cool air flow.
     
  6. Andrew Powell New Member

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    Okay so still on the hot start trail looking for a solution. Just had the injectors out cleaned by injectortune (great service) and tested and all fine so no change once refitted still getting to much fuel ⛽ to injectors at warm start. Followed the 8v set up so far all mechanical side I think is OK starts first time cold and drives lovely just won't start warm and driving me . I've read elsewhere on here if the ecu fails it will keep the injectors open and the fuel pump on all the time. The fuel pump on my vehicle primes and turns off on ignition point 1 so I'm hoping ecu is fine but have a replacement on its way. Can I just check so I don't cook the ecu I need an earth from the battery - to the engine normally on the gearbox housing. I've definitely got an earth on the vehicle body from the ecu but have not tracked an earth from the battery which is upfront in my T25 conversion. I also wondered if a wiring fault generally would result in a similar issue with overfueling as I'm tempted to get my loom spaghetti tested from the ecu pin connection end.
     
  7. rubjonny

    rubjonny Administrator Staff Member Admin

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    did you happen to note the injector part numbers while it was apart? if you're still loosing pressure after switch off try clamping the feed line to rule out everything from that side of the rail. plus you can always pull the fuel rail off engine to check injectors arent leaking

    the reason the ecu gets blown is down to poor engine eath yes, when you try and crank it starter cant earth to battery so it earths thru the ecu instead, plus the cluster if its MFA type. reason it can try this is the ecu and cluster earths to the side of the head, since the ecu also had an earth to battery it goes thru the ecu and kills it. the cluster has an earth path either to fusebox or through various sensors. if worried you could move the ecu head earth elsewhere, then it wouldnt happen even if your earth went bad

    ecu wiring check is definitly a good plan
     
  8. Andrew Powell New Member

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    Thanks for your reply and further advice. Yes the part numbers for injectors were 0280150902 and the injector tester said they were a older more reliable design which uses a 4-hole gauze for a finer mist and he provided a nice test readout before and after cleaning so they are now all ok and none were leaking. We've changed the fpr (Pierburg 3bar)and put a non return valve after the fuel pump but im not convinced the garage tested for pressure appropriately nor did they check the rail wasn't leaking fuel which would indicate the ecu is gone. To be honest I'm struggling to find a garage that will spend time going systamatically through your great setup as most seem to want to work on simple fixes hence my plan to test the wires with an auto electrician and ensure signals are reaching the appropriate bits and the Maf sensor is within parameters etc. I'm not a very good DIY mechanic either so if there is a local enthusiastic one down here who wants some beer money I'd be delighted to receive some on the job help [:D]
    . The following has been done fpr replacement, new distributor, new starter amp, Maf cleaned but I think sensor overiden using dial under sealed cap) timing checked, throttle body cleaned and throttle set up, new spark plugs, air filter cleaned vacuum pipes and hoses checked. None of the above has helped hot starting cold start fine every timr but even after approximately 5 minutes use it takes about 10-20 turns of starter to fire up then drives fine again. My guess after reading too much Google is injectors are open all the time from start flooding engine but any more educated ideas would be most welcome :)
     
  9. rubjonny

    rubjonny Administrator Staff Member Admin

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    yep those are VW 037906031C which come back to digifant PB ones alright.if someones opened the maf and fiddled that could be a suspect
     
  10. Andrew Powell New Member

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    Thanks again I have a spare Maf so I'll do your test on the digital resistance and if OK pop that back in
     
  11. Andrew Powell New Member

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    Okay tested back up Maf 0.664 at pins 3 & 4 2770 1 and 4 which Correlates with resistance curve at house temp of around 20 degrees and between 2 and 3 resistance goes up and down with flap so hopefully spare maff is OK if I'm reading the guide correctly I'll check the Maf in the vehicle later.
     
  12. Andrew Powell New Member

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    Updated the Maf in va. 0.9 at pins 3 & 4 and 1000 which Correlates to outside temp so that looks OK. Interestingly car normally starts first time cold but was differing a little and turned the key to position 1 for longer than normall and same issue I've been getting at hot start it didn't start [8-}] so maybe my injectors are stuck on from ecu
     
  13. rubjonny

    rubjonny Administrator Staff Member Admin

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    have you checked the coolant temp sensor as well, they can fail intermittently. on mine i found it would never ever start first turn of key no matter how long I held it for, but 2nd crank fired right up would run perfect and start again fine rest of the day. new sensor cured it, most odd
     
  14. Andrew Powell New Member

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    New hella coolant sensor fitted but will test it also, just to be sure
     
  15. Andrew Powell New Member

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    So quick update following feedback from auto electrician all wiring from ecu tests fine and good spark but he has discovered that when in cranking mode the injectors are on full bore. He is aware of ecu causing injectors to be always on when blown but he says that is also normally accompanied by fuel pump been always on to which mine isn't and only injectors on fully in crank mode at start. Does anyone know what could be causing this other than the ecu or perhaps associated sensor?
     
  16. rubjonny

    rubjonny Administrator Staff Member Admin

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    its possible the ecu has gone in a different way to the usual, I assume he checked the wiring from injector rail to ecu making sure there were no shorts there? may be worth grabbing another ecu for testing
     
  17. Andrew Powell New Member

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    Thanks I have a spare ecu so will give this a try. I confirm we have checked the earth's before this goes in to be sure there good so we don't cook it. Out of interest if it's not the ECU could anything else send a spurious single at Crank to turn the injectors on fully I was thinking perhaps accelerator pedometer wiring fault. My final question is if this only happens at crank and we can temporarily turn off the full injector signal to help the hot start (like an old choke on/off) is this a sensible fall back to try or would you advise finding the pesky fault as clearly that would be a non standard mod which shouldn't be needed[:-B]
     
  18. rubjonny

    rubjonny Administrator Staff Member Admin

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    Yeah its not common for it to only affect warm start tbh, if they go they're gone for good usually and wont start again no matter what unless board is fixed or ecu swapped...
     
  19. Andrew Powell New Member

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    Thanks I'll update once we close down a few more avenues but at least we know the injectors at crank are the cause of hot start and who knows we might find a future solution for anyone else unlucky enough to experience this fault
     
  20. Andrew Powell New Member

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    Okay so electric system is fine and the problem has been narrowed down to fuel pressure too high as when fuel pipe restricted a bit the engine starts when hot. I've fitted a new 3bar pierburg fpr but am now wondering how else I can reduce fuel pressure perhaps new fuel pump any ideas greatly appreciated but we are nearly there just need a last push to get over the line
     

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