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Thread: Zenith again!

  1. 25th January 2022, 01:34 PM #1
    JDNSW's Avatar
    JDNSW
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    Zenith again!

    This morning I decided to see if I could find why the 2a seems to be intermittently idling very rich.

    I pulled the Zenith off, and took it apart. The only issue I found was that the needle valve seat was not tight. Not really loose, but not really tight either.

    Reasoning that this could allow leakage on the aluminium washer that prevents fuel from leaking along the thread, I tightened it. The side of the washer towards the seat was roughened by the hexagon being tightened against the soft washer in multiple positions.

    A test drive seems to have confirmed the fix.
    John

    JDNSW
    1986 110 County 3.9 diesel
    1970 2a 109 2.25 petrol
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  2. 25th January 2022, 02:00 PM #2
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    Quote Originally Posted by JDNSW View Post
    This morning I decided to see if I could find why the 2a seems to be intermittently idling very rich.

    I pulled the Zenith off, and took it apart. The only issue I found was that the needle valve seat was not tight. Not really loose, but not really tight either.

    Reasoning that this could allow leakage on the aluminium washer that prevents fuel from leaking along the thread, I tightened it. The side of the washer towards the seat was roughened by the hexagon being tightened against the soft washer in multiple positions.

    A test drive seems to have confirmed the fix.

    Hell's bells John, if anyone could fix it you could. Sometimes it is the simplest things that try & foil us.
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  3. 25th January 2022, 06:54 PM #3
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    I had Lean Issues.
    Tightened Carby manifold nuts by 1/2 to 1 turn seem to help.
    I had to retard Ignition by 2 1/2 Degs on my S3 Daily, 3 weeks ago. Not sure 98 coming out the pumps anymore ????
    Few days ago, Different Supplier filling Tanks, at the local Service centre I have used for years.
    No Knock sensor on The old Land Rover !!!!

    whitehillbilly
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  4. 25th January 2022, 08:15 PM #4
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    Quote Originally Posted by whitehillbilly64 View Post
    I had Lean Issues.
    Tightened Carby manifold nuts by 1/2 to 1 turn seem to help.
    I had to retard Ignition by 2 1/2 Degs on my S3 Daily, 3 weeks ago. Not sure 98 coming out the pumps anymore ????
    Few days ago, Different Supplier filling Tanks, at the local Service centre I have used for years.
    No Knock sensor on The old Land Rover !!!!

    whitehillbilly


    You wouldn't hear it if it did knock so simply assume it has one.
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  5. 26th January 2022, 05:57 AM #5
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    There is no problem hearing knocking in a Series if your ignition is too far advanced. You may not be able to hear it at 100kph on the highway - but that is not when it will knock! The first place you will probably hear the knock is when you floor it at 50kph in fourth, or when you increase throttle for a steep bit in second at 15kph.
    John

    JDNSW
    1986 110 County 3.9 diesel
    1970 2a 109 2.25 petrol
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  6. 26th January 2022, 07:57 AM #6
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    Quote Originally Posted by 4bee View Post
    Hell's bells John, if anyone could fix it you could. Sometimes it is the simplest things that try & foil us.
    I think that it was just a matter of knowing how the thing works, and understanding what could cause rich idling. (I have long since found that fiddling with the idling mixture screw is futile in these circumstances!)

    The symptoms suggested that the needle valve was not stopping fuel completely or the float level was too high. So first thing to do was to check the float level - absolutely spot on 33mm, so that was not the problem. Then remove the float and the needle valve. Spotlessly clean, and there was no debris in the float bowl either, and the needle valve looked like new. So next step was to remove the seat to check that it sealed - which was when I realised it was not tight. And that this a likely cause of the issue. Carefully looked at the washer, and reassembled and tightened the seat, and checked by holding the needle in place and blowing through the fuel inlet. Put the float back on and recheck height, then put everything back together again, including a long search for a splitpin to replace the one from the acceleration pump/throttle link I dropped on the floor and could not find. (my box of assorted split pins does not go that small)
    John

    JDNSW
    1986 110 County 3.9 diesel
    1970 2a 109 2.25 petrol
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