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Thread: Mixture setting

  1. #1
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    Mixture setting

    Today, i noticed after removing my fuel distributor that the plunger is jammed in the full load position. After looking at the mixture screw, i found that it is screwed almost all the way down, with maybe 2-3 threads showing at the top. Ive seen diagrams and pictures of the mixture screw and was wondering if this sounded normal to be screwed down that far considering that screw is almost 3/4 of an inch long. Im guessing this is why i found gas in the oil pan?

    Im not at a point right now to fire the motor due to being in the process of replacing all of the fuel lines, filter, pump etc.

    The hole for the mixture screw has the gold colored rod with the rubber plug in the hole. I read that these originally came with an anti tamper plug if im not mistaken.

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    Only way to know if your screw is in the right position is to reset it. Once your system is reinstalled and you can get fuel to your FD, bridge the fuel pump relay (pins 30 & 87) and watch for fuel coming out of the injector line outlet ports of the fuel distributor. The mixture screw (3mm Allen Key) is between the fuel distributor and the air flap.

    If fuel is rising out of the injector line outlet ports, rotate the mixture screw, with a 3mm Allen key, anti-clockwise until the fuel just stops rising. Wipe the injector line outlet ports and watch to see that it has stopped flowing. Turn the mixture screw anti-clockwise a further 45 degrees. This should give you a basic starting point for setting the correct mixture.

  3. #3
    Administrator Ron's Avatar
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    Quote Originally Posted by dmcnc View Post
    Only way to know if your screw is in the right position is to reset it. Once your system is reinstalled and you can get fuel to your FD, bridge the fuel pump relay (pins 30 & 87) and watch for fuel coming out of the injector line outlet ports of the fuel distributor. The mixture screw (3mm Allen Key) is between the fuel distributor and the air flap.

    If fuel is rising out of the injector line outlet ports, rotate the mixture screw, with a 3mm Allen key, anti-clockwise until the fuel just stops rising. Wipe the injector line outlet ports and watch to see that it has stopped flowing. Turn the mixture screw anti-clockwise a further 45 degrees. This should give you a basic starting point for setting the correct mixture.
    Correct me if I'm wrong but, I don't think it is a good idea to pressure up the system with the injector lines disconnected. Seems fuel would go everywhere even if his is not as far off as he thinks it may be..
    ???

    =======

    Not sure if you mean the plunger is seized in the up position or not... Just in case:
    When the engine is running there is fuel pressure pushing the plunger down, which pushes the plate up. When you shut it off some pressure remains for a while. If someone presses the plate down, the plunger will go up (and the plate will flop when you tap on it). If the plunger stays up and sits for a long time, it may seize in that position. It may be that the adjustment screw is OK.

    Running the CO screw down (CW), makes the plunger go up and the A/F richer. As you suspected, if it is was stuck up, the engine would start to flood as soon as you turn the key on. Definitely a source for oil contamination (and washed out rings).

    You could rough in the CO screw as follows:
    Have fire extinguisher ready.
    When everything else is together, put the injectors in a container. Jump the RPM Relay and watch the injectors while someone turns the key to ON only. If they spray, turn the screw (CCW) just past enough to make them stop when you remove the wrench. The CO screw will then be roughed in.

    You are correct on the gold and anti-tamper plugs.

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    Quote Originally Posted by Ron View Post
    Not sure if you mean the plunger is seized in the up position or not... Just in case:
    When the engine is running there is fuel pressure pushing the plunger down, which pushes the plate up. When you shut it off some pressure remains for a while. If someone presses the plate down, the plunger will go up (and the plate will flop when you tap on it). If the plunger stays up and sits for a long time, it may seize in that position. It may be that the adjustment screw is OK.

    Running the CO screw down (CW), makes the plunger go up and the A/F richer. As you suspected, if it is was stuck up, the engine would start to flood as soon as you turn the key on. Definitely a source for oil contamination (and washed out rings).

    You could rough in the CO screw as follows:
    Have fire extinguisher ready.
    When everything else is together, put the injectors in a container. Jump the RPM Relay and watch the injectors while someone turns the key to ON only. If they spray, turn the screw (CCW) just enough to make them stop when you remove the wrench. The CO screw will then be roughed in.

    You are correct on the gold and anti-tamper plug.
    When i say frozen i mean it will not budge at all. There was definatley a bunch of gas in the oil. I just spoke with the previous owner yesterday. I asked him about when he last drove it. He said it ran fine and pulled it into the garage in 2003 where it remained due to health issues.
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    Motors about after dark Michael's Avatar
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    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by Mike1830 View Post
    When i say frozen i mean it will not budge at all. There was definatley a bunch of gas in the oil. I just spoke with the previous owner yesterday. I asked him about when he last drove it. He said it ran fine and pulled it into the garage in 2003 where it remained due to health issues.
    2003 is 16 years ago!! Any fuel in there has turned into varnish (aka glue). Yeah, it's stuck. Wide open. Which is why there is gas in the oil if you've been trying to start the car.

    You can adjust the mixture screw all you want and it's just going to keep flooding the engine. Get the plunger unstuck, or get another fuel distributor, before you go any further.

    As for how to set it, I would recommend the opposite of the initial post. Back the screw all the way out (don't force it, there is a stop). With the injectors attached and pointing into jars, turn the screw clockwise until it just starts to flow thru the injectors and then back off until it just stops. This should run the car. Using the method given, if the screw is really way to far in, you'll probably spray fuel all over the engine. If there are any loose or bad plug wires, you'll set it on fire.
    Dave S
    DMC Midwest - retired but helping
    Greenville SC

  7. #7
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    I found the gas in the oil before i ever even hooked up a battery to the car. The fuel pump is also dead so when i was cranking it, nothing was being pushed through. Im in the process of ordering everything to rebuild the fuel system and have the FD rebuilt or replaced.

    Sent from my SAMSUNG-SM-G930A using Tapatalk

  8. #8
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    Quote Originally Posted by DMCMW Dave View Post
    2003 is 16 years ago!! Any fuel in there has turned into varnish (aka glue). Yeah, it's stuck. Wide open. Which is why there is gas in the oil if you've been trying to start the car.

    You can adjust the mixture screw all you want and it's just going to keep flooding the engine. Get the plunger unstuck, or get another fuel distributor, before you go any further.

    As for how to set it, I would recommend the opposite of the initial post. Back the screw all the way out (don't force it, there is a stop). With the injectors attached and pointing into jars, turn the screw clockwise until it just starts to flow thru the injectors and then back off until it just stops. This should run the car. Using the method given, if the screw is really way to far in, you'll probably spray fuel all over the engine. If there are any loose or bad plug wires, you'll set it on fire.
    Also i havent touched the mixture screw. I just thouggt it was odd that for as long as that screw is that it is in that far. It appeared someone may have been in there before me given the condition of the mixture hole having wheat appears to be tooling marks from possible previous work.

  9. #9
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    Quote Originally Posted by Ron View Post
    Correct me if I'm wrong but, I don't think it is a good idea to pressure up the system with the injector lines disconnected. Seems fuel would go everywhere even if his is not as far off as he thinks it may be..
    ???

    The procedure I mentioned was strictly for reseting the Fuel Distributor once everything else was addressed (loose plunger, system hooked up, etc) - apologies for not clarifying.
    Here are some references for this procedure:
    http://www.cisflowtech.com/frequentl...xture-setting/
    https://k-jet.biz/fuel-distributors/
    http://www.type17.ch/downloads/Injec...p%20Manual.pdf (Page 32)

  10. #10
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    Not a problem. Thank you for all the info.

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