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Unread 05-08-2014, 06:17 PM   #1
trk204
Registered User
1987 YJ Wrangler 
 
Join Date: May 2014
Location: Winnipeg, MB
Posts: 3
87 YJ Chevy v8 ignition wiring issue

Wall of text INCOMING!

Hey guys, my jeep I loved wrenching on for years has unfortunately been sitting in a field for about 6 years now. Well I finally have the time to haul it in and have a look at it.

I swapped in a 305 sbc, 700r4 and dana 300 tcase with all the usual adapters and whatnot. For wiring it, I somehow had a bunch of relays setup with switches for the ignition/fuel (on/off switch) pump and the starter. Somehow, I had a momentary push button rigged up, that had to be pressed, while cranking with the key. It all worked when I parked it! Well sure enough after all these years have the cable runs were water soaked and ruined anyways. So I figured, F it, rip the wiring out and start from scratch when I had no idea where to start troubleshooting

So I tore out the switches and relays, jumped the HEI dist and pump straight to +12, and it eventually fired up. I guess the starter circuit is somewhat functional (more on that later).

I had a look at the wires coming out of the panel on the firewall. And heres the breakdown.

black/yellow (thin wire) - some doo hickey under the starter relay
yellow/black (thin wire) - elec choke (+12v switched power)
black - motor ground by starter relay
red x2 - Thick wire to main lug on starter relay
red/white - Thick wire to main lug on starter relay
dark green - Thick wire to starter
yellow - + 12 to alt little wire

So going with that, I tried connecting up a relay with pin 85 to the yellow/black +12v switched, 86, to gnd. 30 straight to the battery, and 87 to the positive bus I had setup for +12v switched accessories. The ignition, fuel pump and elec choke were on it. Hooked er all up to the batt, turned key to the ON position, relay clicked on, fuel pump kicked in and should be good to go.

Crank the starter, and while the starter is working I can hear (or not hear) the fuel pump. Stop cranking, and it just managed to catch fire, stumble and run, as the fuel pump came back on meaning the whole circuit was without power during cranking, so didn't get +12 to the ignition until I stopped cranking, the black/yellow got full voltage and clicked the relay. I guess there was enough momentum/gas/air in there to make it go.

Turn it off, hook up the volt meter to the black/yellow wire I'm using to drive the +12v accessories, and it drops to around 8v. BUT, before I had all the wiring sorted out I had run the +12v from the alternator to the HEI. Truck would fire up no problem (had the fuel pump connected through a diff wire). But now the truck wouldn't turn off when the key shut off, I guess the alt is still pushing 14v to the dist, keeping it running.

So I guess my problem is this, how can I get enough voltage through the black/yellow wire to drive the sense circuit on a regular bosch type relay. It's probably why I had the hot to the dist wired right to a switch.

Also, my starter relay is a friggin mess. I have no idea whats going on there. I know I had one my switch/relay setups running off the light green/white wire. But now that I've pulled all that stuff out, I don't even have it hooked up and the starter works fine with the dark green wire going straight to it.

I've attached a pic (I hope) of the starter relay wiring.

Other then that, the beast runs!

2014-05-05-19.23.48-txt.jpg   2014-05-05-19.21.01.jpg  

Last edited by trk204; 05-08-2014 at 06:45 PM..
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Unread 05-08-2014, 07:08 PM   #2
superj
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1987 YJ Wrangler 
 
Join Date: Mar 2008
Location: corpus christi, texas
Posts: 6,321
The second pic can just be bypassed, it turns on your 4x4 light on the dash. I believe
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Unread 05-09-2014, 11:57 AM   #3
trk204
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1987 YJ Wrangler 
 
Join Date: May 2014
Location: Winnipeg, MB
Posts: 3
Well hey thats one part I can tear out!

Now just to figure out the ign circuit.
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Unread 05-09-2014, 01:36 PM   #4
dancytron
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1990 YJ Wrangler 
 
Join Date: Jun 2008
Location: st. louis
Posts: 1,213
What you have labeled as "thin alt wire" is the wire that triggers the starter solenoid to crank the starter. What you have labeled "fat alt wires" and "2x red to panel" are fusible links. Not sure where they go, but get the factory service manual and the wiring diagrams will tell you. That post and the fusible links attached to it are the power supply for the whole jeep except for the starter.
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Unread 05-09-2014, 09:07 PM   #5
trk204
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1987 YJ Wrangler 
 
Join Date: May 2014
Location: Winnipeg, MB
Posts: 3
SWEET!!! Thanks for the tip! I just went out there and disconnected the hot wire to the starter so I could hold the key on the start position and not have it crank.

Sure enough the wire I was using to power the relay was getting 0 volts while key was in START. So wrong wire all together. So I cut the little alt wire off the yellow wire, and sure enough yellow gets +12 during ON and START. Bingo. Connect little alt wire right to starter relay and we're off to the races. and the yellow wire to power the relay for the accessories. Everything just works

Last question, that light green white wire coming off the starter relay, am I right in kind of remembering that the jeep starter required you to run through the starter solenoid on the firewall, but the chevy starter has an onboard solenoid? Isn't that why I can send that dark green wire straight to the starter?
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Unread 05-09-2014, 10:11 PM   #6
sketchy
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1985 CJ7 
 
Join Date: Mar 2014
Location: , Oklahoma
Posts: 27
Quote:
Originally Posted by trk204 View Post
...I somehow had a bunch of relays setup with switches ... Somehow, I had a momentary push button rigged up, that had to be pressed, while cranking with the key...
That's my life story right there!
I come up with really clever solutions and the next time it breaks I have no clue what I did.

Quote:
Originally Posted by trk204 View Post
It all worked when I parked it!
The only thing that saves me from being "that" PO is that I never sell anything.

Good luck my brother!
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