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Volvo K24 7400 Rebuild question

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  • #46
    Why does that ECU not have VSS connected - is that an interim fault or something deliberate ?
    Paul Nugent
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    1994 S2 Coupe ABY - aka Project Lazarus
    2001 A6 allroad 2.5TDi - family tank
    2003 S4 Avant 4.2 V8 - daily burble

    Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

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    • #47
      Hey. The VSS fault is one that started over a year ago, prob two now. I think i looked into it briefly last year but never got to the bottom of it.

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      • #48
        I would definitely thoroughly check the injector harness and injector connectors.
        i can supply you a set of the correct gold plated MAF terminals if required - £12 delivered
        Panthero Coupé quattro 20vt
        Indigo ABY coupé
        Imola B6 S4 Avant

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        • #49
          Thanks for the offer of MAF terminals, i actually purchased some off you previously which i've not got round to fitting yet. Would resistance readings on the injector cabling be sufficient to determine what condition they're in? Thanks

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          • #50
            Alright gents, a wee update for you. I've had some success with the problems i was experiencing. First of all i decided to tackle the oil ingress into cylinder 1. After stripping out the cams, lifters etc i found possibly half of the valve stem oil seals across all cylinders had lifted slightly from their seated position on top of the guides. Now how this happened i can not say for sure as they were tapped on using tools for the job, however, i think when i fitted them a couple of years back the tool that i used with the different size pin type attachments for knocking them home, has actually slightly lifted some of them off their seat when removing the tool. They were fitted with the valves out previously. Either that or on fitting the valves back into the head with the newly fitted seals in place has caused them to lift slightly.

            The new valve stem seals have an ID of 6.2mm i think, now if i used the 6.5mm or more so 7mm attachment for fitting them there is a bit of resistance when pulling the tool back out which possibly pulled the seals of their seat slightly. It doesn't take much effort to pull new seals of their seat when fitted, unlike the original ones which needed a good tug.

            The pin attachments are not smooth like the valves are so there is a definite bit of resistance there. Also when i fitted them previously i never used the wee plastic protectors that go on top of the valve. I don't even remember if they were supplied, however this time round they were.

            With the seals fitted correctly i was getting a measurement of around 24.5 - 25mm from the top of the seal to the top of the valve. The suspect ones had a measurement of around 22.5mm to the top of the valve. Only a couple of mm but i guess that's the difference between sealing correctly and not.

            When i was setting TDC for cams removal i noticed that with the cam and crank mark lined up the locking tool wouldn't quite fit. I was wondering why the hell that was but proceeded anyway. On rebuild it dawned on me that a couple of years back i had used the wrong line on the crank for setting TDC. I don't think i realised that the correct crank timing mark is the one with the zero on it which i found hidden under rust!!! Anyhow, once i found the zero line all timing marks lined up and locking tool fitted spot on. Nice one!!!

            I also now realise why i was having issues lining up the dizzy last year. The cam/crank timing had been a tooth out the whole time. You live and learn eh!

            The No1 injector wire that i nicked has been repaired correctly so that's another job of the list.

            As for the Volvo turbo itself i forgot to add to upgrade the spring in the internal wastegate until the correct plug arrives to seal the port correctly. This is another reason, as well as the incorrect timing that i wasn't achieving full boost.

            Now with the car up and running again it idles so much better being correctly timed and drives noticeably stronger from low down. I'm still waiting on the internal wastegate plug to arrive, currently stuck in customs, aaaargh!!! However i've beefed up the loading on the diaphram as a temporary measure and the car boosts real quick now. I've not tried to go WOT yet as the internal wastegate will still probably lift at higher boost pressures so just giving it wee bursts here and there to get a feel for it.

            I'm pleased to report now it spools so much faster than it did a couple of weeks back. Nice low down torque, with fast boost onset. Looking forward to trying WOT. So far so good!

            There is now no oil ingress into cyl one either, nothing but a nice clean piston top and plug to be seen. Yippee!

            The VSS fault code i was getting was checked out, all the wiring from the sensor to the clocks etc was checked and everything appeared normal. The only suspect thing i found was oil in the 3 pin connection on the side of gearbox. I blew that out with compressed air and refitted everything, to date the fault coder hasn't returned and my average MPG etc has been working constantly. Hopefully it was just the oily 3 pin plug that was the issue all along?

            So i just await the wastegate plug now to blank off the port and hopefully i'll be getting full boost pressure.

            Watch this space!
            Last edited by gmac78; 19 June 2018, 20:45.

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            • #51
              Glad you've managed to get to the bottom of all your issues and that the oil ingress was nothing more than the oil stem seals we mentioned earlier. It sounds like it's all coming together very nicely now and liking what you've said so far about the turbo now she's timed up properly. Do you think the Cobra intake hose could potentially cause any issues with holding the turbo back? Do you have a link for this upgraded internal wastegate spring?

              96 URS6 plus speck saloon
              96 URS6 plus speck estate
              94 2.6 80 Avant
              99 2.8 final edition Cabriolet

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              • #52
                Well that thought has crossed my mind as a Cobra head is slightly more restrictive than a conventional 90 Deg elbow but it's the only way to make it work.It's so so tight!!! For the power this turbo will put out i'm not sure it's going to cause too much of a restriction. If certainly feels strong now from low to mid revs and that's only taking it up to 1 bar boost until the blanking plug arrives. Don't want the bypass to be lifting and over spinning my new turbo, which i've already done anyway but that's because i had forgot about beefing up the spring tension. Got an email today saying the blanking plug has cleared customs so hopefully get it soon.

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                • #53
                  Your probably right, this turbo won't be asking for huge amounts of air so the Cobra head could very easily be more than enough and of course fully appreciate how tight it is in there. Loving what your doing here as you know i bought (Andy10v) K24 - 7400 turbo with the Porsche K26/6 hotside yet to be done, so seeing you do this and the fact that mine has also been on the shelf for nearly 4 years it's fabulous to see another member take the horns and run with it. I've got this gut feeling from all the nuggets of information about it that this is one special turbo.
                  96 URS6 plus speck saloon
                  96 URS6 plus speck estate
                  94 2.6 80 Avant
                  99 2.8 final edition Cabriolet

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