Fuel in QV Intake manifold | FerrariChat

Fuel in QV Intake manifold

Discussion in 'Technical Q&A' started by Crockettsonny84, Oct 9, 2013.

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  1. Crockettsonny84

    Crockettsonny84 Rookie

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    Ive been battling a fuel mixture issue for a couple weeks now and have came to the point where the car will not start.

    Before I began messing with the mixture, the car was idling rough, smelled extremely rich, and would stall during deceleration. Doing my research, I performed the ground mod on the digiplex boxes, cleaned the grounds for the coils, replaced plugs, plug extenders, and replaced the fuel filter (which by the way was extremely dirty).

    Upon having that all sorted I "played" with the throttle set screw, AAV screw, and mixture adjusting screw. (Really, I have no clue how to adjust these to correspond with each other.) I DID set the mixture screw in accordance with the "initial setup" that Bosch recommends. When attempting to start fuel was found flooding up into the intake manifold at the throttle plate.

    Cant really tell if thats the initial cause of my problem, nor do I know if it's a problem with the injectors or distributor plunger leaking.

    Any advice on what setup I need (i.e. where the throttle/aav screw should be positioned) to get the car to start and stay running? How do I clear the intake of excess fuel? and does anyone have a solution to rid the standing fuel at the throttle plate? Any help would be greatly appreciated!
     
  2. miketuason

    miketuason F1 World Champ Owner Silver Subscribed

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    It's possible that your cold start valve/injector might be defective as in always on even after the car has warmed up. Try to unplug the blue terminal of the cold start valve that is on the right side of the plenum and see if that makes any difference. If the cold start valve is always on, you will always run rich and you'll see fuel from the throttle body all the time and will never run right.
     
  3. Crockettsonny84

    Crockettsonny84 Rookie

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    Now, is it possible that the valve can stick open and dump fuel without being electrically connected?
     
  4. st@ven

    st@ven F1 Rookie

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    Unplugging it might not show it. Better remove it from the plenum , keep electrical and fuel line attachéd en put it in a stable Bucket. Ask a friend to start the car. If cold it Will spray for ( from my head) 8 secondes. If really warm it should not spray at all. If it continues pull the blue plug. It should stop spraying.

    Edit. Crocketsonny suggestion is basically the Same failure. By removing the noodleiding you can simply see what's happeninh
     
  5. Crockettsonny84

    Crockettsonny84 Rookie

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    Alright, Ill give it a go and return with the results.
     
  6. st@ven

    st@ven F1 Rookie

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    But Heads up on safety!
     
  7. Iain

    Iain F1 Rookie

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    Fuel at the throttle plate in the throttle body on the plenum can only really have come from the cold start injector.

    Re setting up the idle,

    Piece of paper at the throttle screw & then screw it down till it just touches/grabs the paper. Then add 1/2 a turn. Then adjust the idle speed with the air bypass screw/nut under the throttle body.

    Re the mixture adjustment screw, if you mean the thing on the injection unit it would be so much better if you hadn't touched that! An adjustment of just a few degrees makes a huge difference & to set it up correctly you really need a properly calibrated gas analyser. There are (literally) 101 different reasons a CIS car might be idling badly or running lean or rich, but unless its been messed with previously, the mixture adjustment is about the last thing you touch.
     
  8. miketuason

    miketuason F1 World Champ Owner Silver Subscribed

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    Yes, it's possible.
     
  9. Crockettsonny84

    Crockettsonny84 Rookie

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    Alright, I pulled the CSV and as it turns out, it was the cause. Spraying too much fuel for too long. It does shut off when the plug is pulled so I just left it off for now so I could tune the engine

    Now my problem is: trying to get the car to run right. It's missing at idle and low RPM (1500-2000). I would point to ignition, but what could I check? How can I diagnose whether or not it's a digiplex problem?
     
  10. Iain

    Iain F1 Rookie

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    Its unlikely to be a digiplex issue - they either work or they don't & if you'd lost one , you'd lose a whole bank.

    After having raw fuel thrown down its throat the plugs are probably fouled. If you wanted to then you could take the distributor caps off & check the plug leads for continuity but before you do that check the extenders & make sure none of them are burned through - that can often be the cause of bad idling.

    Look for bad hoses & vacuum lines as well, the thing need to be airtight to work right.

    As above, if you adjusted the CIS mixture you really need a gas analyser to straighten it out again.
     
  11. cmt6891

    cmt6891 Formula 3

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    The one ignition component that ceratinly needs replacement from original is the iginition wires. Simplest and best way to go about that is contact SRI, aka Dave Helms.
     
  12. Crockettsonny84

    Crockettsonny84 Rookie

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    I understand that Cavis was the original wire manufacturer. Im not entirely sure what brand mine are but I do know that they are red with an integrated boot.

    EDIT: regardless, they are gonna be replaced
     
  13. cmt6891

    cmt6891 Formula 3

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    Yes Cavis are the original wires but they are black. The sheathing and boot, which are red, need to be removed to expose the wire.
     
  14. Crockettsonny84

    Crockettsonny84 Rookie

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    So, I got around to putting new wires on the car. I went with the Birdman suggestion of using the Accel wires, but I got the 5040R's due to availability of the 4040R's. As mentioned, the 8mm wires had to be trimmed a little bit to fit in the holes of the distributor and at the moment I dont feel like Im getting good contact.

    With the car running, the rear bank is putting out plumes of white smoke from the exhaust. It is still stumbling. I wouldve figured a head gasket problem but upon further investigation, the plugs on the rear bank are covered in fuel and the dipstick doesnt show any signs of coolant. Any ideas?
     

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