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Thread: 1973 75/5 back firing and no power

  1. #1
    chiefclint
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    1973 75/5 back firing and no power

    I got caught in a rain storm the other day, took my time made it home slowly but as I got closer I noticed that the engine was losing power. Got home, thought it might just need to dry out....well the next day it was backfiring and no power in first gear, once it did get going it would spit and spurt. The pressure from the exhaust is noticeably weaker on the rhs and the rhs plug was all black. The lhs one was a little dirty but really nothing to mention. ideas?

  2. #2
    Liaison 20774's Avatar
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    First thing I thought of is that water is trapped in the points compartment on the front of the engine. Disconnect the battery ground(s) and remove the front cover. See if any water comes out. Might want to put a hair dryer to the area anyway. See if that helps. Be sure and reconnect the battery ground(s) after you replaced the front cover!
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  3. #3
    Registered User mneblett's Avatar
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    Quote Originally Posted by chiefclint View Post
    I got caught in a rain storm the other day, took my time made it home slowly but as I got closer I noticed that the engine was losing power. Got home, thought it might just need to dry out....well the next day it was backfiring and no power in first gear, once it did get going it would spit and spurt. The pressure from the exhaust is noticeably weaker on the rhs and the rhs plug was all black. The lhs one was a little dirty but really nothing to mention. ideas?
    Quote Originally Posted by 20774 View Post
    First thing I thought of is that water is trapped in the points compartment on the front of the engine. Disconnect the battery ground(s) and remove the front cover. See if any water comes out. Might want to put a hair dryer to the area anyway. See if that helps. Be sure and reconnect the battery ground(s) after you replaced the front cover!
    If it was water in the front cover, both sparks would be weak, as this is a wasted-spark design (each point opening fires the plugs simultaneously in both cylinders). Since it appears to be only on the RHS, and the RHS plug is black (suggesting fuel delivery is still ok on that side), and further assuming the LHS plug is still the normal tan, it sounds like the issue is isolated to the RHS ignition -- either a problem in the RHS plug wire or the RHS coil (nonetheless, I'd still pull the RHS float bowl to inspect/verify no water in the fuel before proceeding -- a quick and easy check to rule out that as an issue).

    First thing I'd do after putting a fresh or cleaned-up plug in the RHS is swap the plug wires to see whether the problem stays on the RHS or moves to the LHS. I'd then swap the coils to see if the problem moves. Assuming that the problem really is in the ignition system, between the four possible combinations you should be able to deduce which component is wet and/or dying. My money is on the RHS coil (assuming, of course, you don't find something simple like a loose connection or broken/intermittant wire).

    HTH -- let us know what you find!

  4. #4
    chiefclint
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    all good ideas, I will take a shot at it tomorrow when I get sometime, thanks.

  5. #5
    chiefclint
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    faulty spark plug wire was it. Swapped those and the spark plugs and the exhaust discharge pressure changed to the lhs. Thanks for the help.

  6. #6
    Registered User mneblett's Avatar
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    Quote Originally Posted by chiefclint View Post
    faulty spark plug wire was it. Swapped those and the spark plugs and the exhaust discharge pressure changed to the lhs. Thanks for the help.
    Great! I love a happy ending

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