Engine Cut out

Discussion in 'Z32 Technical' started by Howard, Jun 4, 2018.

  1. Howard

    Howard New Member

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    OK so as soon as you fix one problem another comes along. At high revs the car backfired once on the LHS looses power and finally the engine cuts out and wont restart. Leave it for a day and it restarts and runs OK then the same thing happens again. Runs fine at low revs. Thinking it must be the PTU although I have not long changed it for a Series 2. The PTU was secondhand. UK car Twin Turbo. Any help most appreciated.
     
  2. beaver

    beaver southern zeds

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    Was the engine running normally before you changed the ptu? What other problem did you fix?
     
  3. Howard

    Howard New Member

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    Had a problem for sometime car would not rev past 5000rpm. Finally found that the pipe had come off the RHS intercooler - hard to believe, it was just touching. Now the car is fine apart from this new problem. Don't think the new problem is connected but I changed so many things I may well have installed a faulty unit. Changed most of the engine wiring, all connectors to coil packs, injectors, cas, ptu, AAV, changed all coil packs, injectors. The diagnostics shows no faults.
     
  4. beaver

    beaver southern zeds

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    Ok, try a known working ptu howard, i remember when I hard wired a new s2 ptu to my car, the engine misfired and generally ran like shit, the problem was a rubbish solider joint, my own fault. Any incomplete wiring contact to the connectors you have replaced wont necessarily through a code 100% of the time.
     
  5. Howard

    Howard New Member

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    OK so I've spent a bit of time on the car today. It now wont start at all which in a way is better. Have tested the PTU as per manual and checked for spark and both OK. Checked the CAS as per manual OK. Only thing I noticed is that the fuel pressure drops off very quickly - less than a minute, when you switch off the ignition, it doesn't happen every time. Clamp the return hose and it still drops off so I suppose this suggests an injector or injectors is passing. May explain the fault in that the engine floods loss of pressure at high revs and the fuel evaporates overnight allowing a restart. On eBay there is a guy in Australia selling replacement new standard injectors. So I suppose this is the next step. Thanks for your help.
     
  6. rob260

    rob260 Moderator Staff Member

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    Only skim read your last response but if you suspect it’s over fuelling then replacement o rings are more likely to fix it than a replacement injector
     
  7. East Coast Z

    East Coast Z Well-Known Member

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    Perhaps it is misfiring at higher RPM due to a lean condition, not a rich condition.
     
  8. beaver

    beaver southern zeds

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    Some after market fpr don't hold fuel pressure like the stock reg does, they bleed down quite quickly compared to the stock reg, which is normal, but a minute is really quick. If you've clamped the fuel return hose and the fuel pressure still bleed down relatively quickly, its likely you have a fuel hose leak at a clamp, injector o'ring leaking, or both.
     
  9. geron

    geron National Petroleum Equipm

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    Perhaps check the fuel filter as well to ensure it's not caked with carbon deposits.
    If somewhat blocked I guess it will cause a lean situation. How's the O2 sensors? they are getting on to nearly 25+ yo if they are still original.
     
  10. Howard

    Howard New Member

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    So I've had a further check, managed to get the car started but runs very badly. Checked compression and all 3 cylinders on the LHS are low <50. RHS OK. Thinking this must mean the cambelt may have jumped have just checked and its OK. Anything worth checking before removing the heads? The petrol thing was another red herring. Thanks.
     
  11. Chrispy

    Chrispy Pretentious Upstart

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    Could be a jumped cambelt or even the locating pin on the intake cam shaft that locates the VTC gear.
     
  12. East Coast Z

    East Coast Z Well-Known Member

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    Prior to thinking about removing cylinder heads it may be worth while removing all the spark plugs & inserting a video inspection camera in the cylinders with low compression.
    You mentioned in your opening post this problem appeared at high RPM.
    What was the approximate high RPM figure?
    What are the compression figures on the other bank of cylinders?
     
  13. Howard

    Howard New Member

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    Checked the locating pin on the intake cams and both OK. Did a better compression test on a cold engine and found 1,3 and 5 about 100-130 and 2- 30, 4-50, and 6-30. The engine has never been opened so seems overdue. The manual mentions that the heads can be removed without removal, is this practical? Am assuming the problem is with the valves as the car doesn't smoke or use oil. Thanks for your input will let you know the outcome.
     
  14. IB

    IB ?????

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    Did you count teeth on the belt?

    I've taken heads off with engine in but it's easier to take the engine out and work on it on a stand.
     
  15. Chrispy

    Chrispy Pretentious Upstart

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    Way easier to do it with the engine out. And allows you to give everything a proper clean and replace all the hoses etc.
     
  16. stumagoo

    stumagoo Active Member

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    yep what ever time you may save not pulling the engine you will lose in skinned knuckles - tools lost down the side of the engine and swearing.... pull the engine for sure
     
  17. East Coast Z

    East Coast Z Well-Known Member

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    Compression test indicates both banks of cylinders are extremely low on compression.
    You could be looking at a total engine rebuild.
     

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