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  •  » How a Starter Solenoid is supposed to work?

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    4/11/2021 9:25 AM  #1

    TremendousWand
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    Registered: 5/16/2013
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    How a Starter Solenoid is supposed to work?

    1996 Mustang Coupe, 5.0 HO Swap, EFI, T5z

    I'm troubleshooting a no crank issue.  

    Please note:  THIS WORKED BEFORE I TOOK IT APART.
    I have the NSS wire connected thru the NSS cable in the T5.  (Just for anyone wondering, this means that the car will only crank if the transmission is in neutral)  Been wired this way for close to a year.  I had to pull the transmission to replace the rear main seal and now upon putting it back together I get no crank. 

    1)  I checked the continuity on the transmission wire it self and it's good.  It only passes current in neutral.
    2) I pulled apart the ignition switch and tested it.  Passes current as intended at ACC Only, KO, and KOEO.
    3) I checked continuity to the NSS wire to the NSS wire on the transmission and I was good.
    4) I checked for power at the starter solenoid and battery side terminal is powered but at the NSS terminal I get no power when the ignition is in the KO position.


    My understanding is that when in the KO position and the transmission in neutral I should get power passed to the NSS terminal on the starter solenoid to allow the current to pass on to the starter.  Is that correct?  I just use a light indicator to check for current and get nothing when I turn the key.  If I am supposed to get power to that terminal when ignition is in the KO then that would mean I have a wiring issue between the ignition and the NSS terminal.  Otherwise, I was going to pull the starter today and do a bench test.  If the starter was having issues I would at least hear some effort of it trying to turn and I hear nothing.  And like I said, it was working before.

    Thank you

     

     

    4/11/2021 10:06 AM  #2

    John Ha
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    From: Mitchell, SD
    Registered: 4/02/2013
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    Re: How a Starter Solenoid is supposed to work?

    1996 or 1966?  For a 1966:

    The starter solenoid is energized when there is power to the "S" terminal (it's the small side terminal that normally has a red/blue stripe wire attached to it) and power to the battery side of the solenoid.  If the solenoid is not energizing, then you need to check whether you have power to the "S" terminal with the ignition switch in "start" (fully clockwise).

    If you don't have power there follow the electrical trail back until you've found the issue.  It goes back to the ignition switch through the bulkhead connector on the firewall, then through the Neutral Safety Switch.

    If you do have power there, then reconfirm that you have power at the battery side of the solenoid.  If you do, your solenoid ground may be bad (it grounds to the body through its metal mounting bracket) or your solenoid may be bad.

    Last edited by John Ha (4/11/2021 10:12 AM)

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    4/11/2021 10:57 AM  #3

    Nos681
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    From: Atlantic Mine, Michigan
    Registered: 7/14/2016
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    Re: How a Starter Solenoid is supposed to work?

    Do you have a drawing of how you actually wired this?

    Have you checked your connections at firewall pigtail?
    66’s had the backup and neutral start switch connector in a 4 wire plug pigtail.

     

    4/11/2021 3:18 PM  #4

    BobE
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    From: White Plains, NY
    Registered: 4/04/2013
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    Re: How a Starter Solenoid is supposed to work?

    Try jumping the battery terminal on the starter solenoid to the "S" terminal on the solenoid, make sure your in neutral, the engine should crank.  If it doesn't crank, check the battery connections on the battery and solenoid.
    If it cranks, pull the "S" wire on the solenoid, and using a test light, or voltmeter, see if you're getting power to the "S" wire.  If not, something is wrong in the ignition switch wiring.
    I'm not sure of the terms "KO" and "KOEO", please define.

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    4/11/2021 5:44 PM  #5

    HudginJ3
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    From: Cedar Hill, TX
    Registered: 4/29/2015
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    Re: How a Starter Solenoid is supposed to work?

    KO = Key On
    KOEO = Key On Engine On

    70, ragtop 351W/416 stroker Edel Performer heads w pro flow 4, Comp roller 35-421-8. T5
     

    4/11/2021 6:01 PM  #6

    Bullet Bob
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    From: Montrose, Colorado
    Registered: 4/01/2013
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    Re: How a Starter Solenoid is supposed to work?

    Actually Doug, KOEO refers to "Key On, Engine Off" in the Ford test procedure.  KO, ER is the engine running test.  KOEO test will not show open (fault) on the start ckt.  Only ckts that the EEC controls.
    Wand:  I didn't see anything in your notes to indicate you checked the start ckt with the ign. sw. in START.  Did I miss something?

    BB1

    "you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
     

    4/12/2021 9:06 AM  #7

    TremendousWand
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    Registered: 5/16/2013
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    Re: How a Starter Solenoid is supposed to work?

    So checked continuity to the S terminal of the starter solenoid.  I jumped the NSS wiring and I got connection to the S terminal and the vehicle actually cranked and ran for about 10 seconds.  Only problem is the vehicle was cranking with the ignition in the KOEO position.  Obviously it's only supposed to crank in the start position...  I'm wondering if I swapped wires when putting the ignition back together.  Will double check today.

     

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    4/12/2021 3:55 PM  #8

    BobE
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    From: White Plains, NY
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    Re: How a Starter Solenoid is supposed to work?

    Check the two small wires on the solenoid.  For the normal 65-66 Mustang wiring the "S" terminal (closest to the cable from the battery) is 'Red-Blue', the "I" terminal wire is 'Brown".
    The brown wire will have reduced voltage with the ignition switch in the "on" position, this may explain why the solenoid may not energize every time.
    The red-blue wire will only have power with the ignition switch in the "start" position.

    Thank you to HubginJ and BB for the acronym meanings. 

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    4/13/2021 10:19 AM  #9

    TremendousWand
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    Re: How a Starter Solenoid is supposed to work?

    I don't have the brown wire for my setup.  I switched to a 3G alternator few years back along with it being an EFI setup.  I only have the NSS wire which goes to the S terminal.  It's only passes signal when the transmission is in neutral.  

    As it stands now... when I by pass the NSS switch on the transmission it cranks on the KOEO position.  When I connect the NSS wire I get no crank, but I can hear the fuel pump activating.  

    Going to call painless wiring and see if they can give some input.

       •Thread Starter
     

    4/13/2021 12:52 PM  #10

    BobE
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    From: White Plains, NY
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    Re: How a Starter Solenoid is supposed to work?

    My mistake, I misread that this is a 1996 Mustang, thought is was a 1966.
    Still, the starter should only crank when the ignition switch is in the 'start' position. 

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    4/18/2021 6:46 PM  #11

    TremendousWand
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    Re: How a Starter Solenoid is supposed to work?

    Just closing this out... Turns out the wires for the harness side connector on the NSS had been pulled out of the connector enough that they weren't actually making contact.  And just to put a cherry on the cake, I had swapped the terminals wires on the ignition switch for the NSS and accessory by mistake.

       •Thread Starter
     

    4/19/2021 9:07 AM  #12

    BobE
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    From: White Plains, NY
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    Re: How a Starter Solenoid is supposed to work?

    You fixed it, all is good.

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

     

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