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  1. #26
    FEP Senior Member Sask84gt's Avatar
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    Quote Originally Posted by qikgts View Post
    I think that makes perfect sense. Maybe hot in run isn't needed at all with a carb.

    Thinking more about it, the only time it may matter is if there is a long crank time and the bowl goes dry from pumping the throttle. And even then, I guess it's not a big deal to just stop cranking and let the bowl fill again.

    If you run it switched power can you report how it works out? I'm always open to learning something.

    Another edit to a post in this thread.... Jeez.... : I just found this link and there is no mention of using a hot in crank and run. I do like the oil pressure switch they used though.

    https://www.hotrod.com/articles/safe...l-pump-wiring/
    Ya that's what was confusing me because everywhere I read there was no mention of hot during crank. I read that article you posted as well. I also bought a oil pressure switch as a safety feature but don't really understand how to hook it up yet. I'm going check fuse box tomorrow hopefully. I'm thinking that fuse 18 will be the 12v switched I'm looking for. Will report back. Thanks for all your help man!
    Last edited by Sask84gt; 12-27-2020 at 06:49 PM.
    Mustangs
    84.5 Gt T-top
    85 Gt

  2. #27
    FEP Senior Member Sask84gt's Avatar
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    So after probing the fuse box with a multimeter I can report that qikgts was right and there is indeed no switched fuse that is hot on crank. There are some constant ones and the one I checked was hot on crank also. So I'm going to try tapping into a switched fuse #5 and see how it works. If it's a pain I will move to a constant and control pump with my switch.

    So to help anyone else looking to do the same thing Here is a break down of what all the fuses are. I did not check the big silver fuse locations as they are circuit breakers. You can reference the lmr drawing on first page of this thread or just search it up.
    #1 constant
    #2 circuit breaker
    #3 open
    #4 constant
    #5 switched
    #6 switched
    #7 open
    #8 constant
    #9 switched
    #10 constant
    #11 switched
    #12 circuit breaker
    #13 switched
    #14 circuit breaker
    #15 open
    #16 constant
    #17 open
    #18 switched
    I checked all the switched fuses regardless of amp size and they all dropped on crank. Hope this will help. I will report back on how the switched source is working once I get it running. Still have some stuff to do.
    Mustangs
    84.5 Gt T-top
    85 Gt

  3. #28

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    FYI the white wire that feeds the duraspark ignition box from the ignition switch should have 12V on both crank and run for the ignition system (maybe one of the only sources for this ?). If you ran constant 12V through a relay triggered off of this source you could have pump on during crank and run if you like.

    However I agree I don't think it is really necessary to fuel during crank if your carb bowls are full. Besides the moment you key on the fuel pump should fill them right away to get you going.

    Hope that helps.

  4. #29

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    I assume your thinking of having an oil pressure switch to shut the fuel off when engine isn't running ?

    That's kind of a catch 22 to get it started unless you incorporate some sort of timer bypass for startup etc.

  5. #30

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    20 White wire with blue hash (W LB H) according to the 1983 diagram anyway. Interestingly (as mentioned before) it also looks like that same wire splices with 904 LG-R that runs to the voltage regulator harness.

    If that stuff has been removed perhaps you can still find the old wires on the connectors etc. Although it is ignition switched the upstream source appears to come direct from the main fusible link from the battery.

  6. #31

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    OK yeah should have read the oil switch article before I spoke. It is a neat idea using a 3 pole oil pressure switch for start/run like that.

  7. #32
    FEP Senior Member Sask84gt's Avatar
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    Quote Originally Posted by at_the_junkyard View Post
    I assume your thinking of having an oil pressure switch to shut the fuel off when engine isn't running ?

    That's kind of a catch 22 to get it started unless you incorporate some sort of timer bypass for startup etc.
    Well I bought a oil pressure safety switch but haven't wired it in yet. Going to have to do a little research and learning to get it wired up. Today I used a fuse tap into fuse location 5 and wired it to a switch. Used original 15amp fuse on the bottom and a 7.5 on top for the pump. When I put key in and turn ignition on with my switch on my pump runs. Everything seems good. Going to leave it like that for now and get everything else ready for a start up. Once I get it running right and make sure there are no fuel leaks etc I will look into the oil pressure switch.
    Mustangs
    84.5 Gt T-top
    85 Gt

  8. #33
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    If you run out gas, you'll have to remember to turn the ignition on for a while to let the pump run to fill the float bowls. Otherwise you could crank forever.

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