Flooded 300ZX engine

Discussion in 'Technical' started by AAU54U, Aug 4, 2012.

  1. AAU54U

    AAU54U Member

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    This is fairly basic and most of you will know this but for newbies like me (and newbies searching the topic) I'll recount my discovery today of how to fix a flooded engine.

    First - how my engine flooded: For whatever reason my car needs to idle at about 1000rpm to avoid the revs dropping too low to zero and motor stopping when you take foot of the accelerator and go into neutral (from high rpm) sort of like the inertia of dropping revs keeps going below idle speed and hits 0 (I know dropping revs doesn't have inertia just what it looks like the needle is doing). Maybe someone can explain that. Note that replacing ECU and idle control valve and TPS has not changed this (I didn't change them to fix this but for other reasons but it hasn't fixed it anyway). Anyway my recent tune at the mechanics had idle reset to 750 rpm which sounds about right for a normal 300ZX (but not mine). After car warms up and been driving a while idle drops to 500rpm and that is where the occasional engine stalls occur as described above. It probably doesn't help that after my recent tune engine at start up is on the rich side (but at least it starts straight away now not after several seconds like it used to).

    My NRMA adventures: So for above reasons my car stalled 3 times in quick succession on way home (slow moving stop start traffic). I was observing how the revs had dropped to 500rpm at idle and thinking how I need to turn the idle screw up when I got home. But I didn't get that far. Instead I stall on busy Windsor Rd near Churchill drive and cause a major traffic jam for half an hour (traffic too busy and no where to push Z to in order to get it off the road - on hill) before NRMA tow truck finally arrive. Then wait another hour for NRMA mechanic to turn up. NRMA mechanic observed engine is flooded and determines that fuel is flowing to engine. Says he has no idea how to get to spark plugs to check spark. Basically throws up his hands and says he cannot do any more because he knows nothing about the engine. He calls tow truck again (same one) who arrives an hour later. I get tow truck to take car to my home.

    How I finally fixed my flooded engine: At home I look up the internet for how to un-flood a severely flooded engine (apart from wait a day). Disconnecting the fuel pump fuse and turning engine to burn off flooded fuel is suggested. I see someone has also done this for a Z. So I take fuel pump fuse out and turn engine several times with throttle fully depressed (to let max air in - no fuel is getting in). I then replace fuse and try to start car. Car starts instantly, works a charm. Fixed it without spending a cent (and NRMA guy wanted to tow me to my mechanics).
     
  2. rob260

    rob260 Moderator Staff Member

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    Right foot to the floor is usually a good fix for flooded engines too...
     
  3. dieseldave

    dieseldave Well-Known Member

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    Sounds like you have an injector or two that are fouled.
     
  4. AAU54U

    AAU54U Member

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    My net search on the topic revealed that some cars stop fuel flow (without needing to take pump fuse out) with foot to floor but that it doesn't work for Zs. So usually but perhaps not Zs?
     
  5. AAU54U

    AAU54U Member

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    Oh so it does work for Zs too.
     
  6. AAU54U

    AAU54U Member

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    Thanks for the advice
     
  7. AAU54U

    AAU54U Member

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    Maybe, but I would be surprised with all the fuel cleaner I've been using (as octane booster)
     
  8. dieseldave

    dieseldave Well-Known Member

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    The "tune up in a bottle" reall do bugger all.
     
  9. Wasgood

    Wasgood New Member

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    Using fuel cleaner as octane booster?

    Either use injector cleaner, or octane booster, they're for different purposes, even though octane booster occasionally will advertise they will do the same things as injector cleaner.
    I've heard we shouldn't run injector cleaner with our injectors anyway.
     
  10. mholt

    mholt Member

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    You are supposed to thank him down the bottom there
     
  11. AAU54U

    AAU54U Member

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    Their cleaning effect is probably overrated by the octane boost of the product I am using us real.
     
  12. AAU54U

    AAU54U Member

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    Actually they often use the same chemical and just label them differently.

    The product I use is Nulon total fuel system cleaner. It is not sold or advertised as an octane booster in anyway. Its manufactureres make no octane boosting claims for it at all. However this test

    http://www.pexcom.com.au/z32cms/e107_plugins/content/content.php?content.13

    shows that it is one of the most effective octane boosting agents on the market. And may even clean your upper cylinder and injectors as well that being its advertised purpose.

    The product which is an even better octane booster is Nulon Pro Strength Octane Booster. I do not use it because it is based on a different chemical that leaves a residue behind that turns your cylinders orange (or something lik that) with long term use.


    I have read that too. Apparently it degrades the insulation on the injector coils or something. I am hoping that the newer chemical (forget its name and not about to do the net research again) that the nulon cleaner is based on will not be as bad in the is regard as older cleaner. I might be wrong of course. If so I replace thet injectors ($1000) I know. But that is nothing compared to what I have spent on the Z already (about to buy a $2.5 K clutch for example).
    Till then I keep using the product and see how it goes. (Throwing money at the Z is fun).
     
  13. rob260

    rob260 Moderator Staff Member

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    You don't need octane booster.

    You don't need a 2.5k clutch either...

    Only thing being cleaned is your wallet.
     
  14. AAU54U

    AAU54U Member

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    My mind says you're right on both accounts. My heart says I need the 2K RPS twin plate carbon carbon clutch.
     

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