Help '99 7.3L wonít crank 5vdc on trigger wire - Diesel Forum - TheDieselStop.com
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post #1 of 6 (permalink) Old 10-28-2018, 12:39 PM Thread Starter
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Help '99 7.3L wonít crank 5vdc on trigger wire

Help 99 7.3 wonít crank with the key
Had to push button start it for time being

I changed the nss on trans still nothing
Starter sel in firewall trigger wire has 5vdc when truck is off and when on
Turned the nss 0vdc on trigger wire on sel and lost reverse lights, bought a new nss today and put it on same thing

If you turn key forward to start a relay clicks and nothing happens still have to use push button my buddy meters it when I tried the key and Iím getting 9.6vdc at trigger wire orange one on the starter sel on firewall but still reading 5vdc when key is off. ***??? Iím stumped.

Any help is appreciated

8143419056 feel free to call or text
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post #2 of 6 (permalink) Old 10-28-2018, 03:33 PM
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Have you checked voltage at the fuse box under the hood? Possibly bad connection between it's power feed at the fender mounted starter relay and the fuse box. You said in your other post that the batteries and alternator were good, but there are lots of other places that you can lose voltage.

Your issue could be a bad ignition switch. There are 5 separate switch circuits built into it, and the one that controls the starter relay could be messed up, with a high resistance connection across the switch when it's supposed to be off. Maybe a melted piece of contact rattling around inside.

I'd suggest checking the ignition switch. Pull the switch connector off and connect your meter set on ohms or continuity (beep function if it has one) across the terminals marked B4 and ST. You should only have continuity with the key in Start position and every other position should show open circuit.

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post #3 of 6 (permalink) Old 10-29-2018, 07:29 PM Thread Starter
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I meters it today and I have 5.36vdc on the harness light blue and red starter wire I think it’s somehwre else now what feeds that starter wire with power
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post #4 of 6 (permalink) Old 10-29-2018, 10:36 PM
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How about your under dash fuse box? Is there evidence of water leakage thru the windshield? That can cause problems with shorting between fuse box traces inside, and could result in something below battery voltage showing up on a circuit that's not supposed to have voltage with the ignition switch off.


Here's a post with some pictures.
https://www.thedieselstop.com/forums...sembly-310910/

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Last edited by klhansen; 10-29-2018 at 10:38 PM.
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post #5 of 6 (permalink) Old 10-30-2018, 01:39 PM Thread Starter
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Wow that’s. Nuts I will check that
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post #6 of 6 (permalink) Old 12-24-2018, 12:03 AM
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I just went thru this after my truck went off cranking itself.

Culprit was a bad GEM from water leaking down the pillar at windshield.

It corroded the heck out of the fuse box plugs and I'm guessing shorted something out.

I put in a GEM from a 99 f150, it cranked at key but all kinds of stuff did not work.

I've currently got an excursion GEM gasser in it and most everything works but having trans issues.

I had 4v on the start wire and a few other fuses.
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