12v IGN source thats hot during crank? - Team Camaro Tech
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post #1 of 7 (permalink) Old May 4th, 16, 07:16 AM Thread Starter
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Casey
 
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Question 12v IGN source thats hot during crank?

What do most of you guys tap into for the 12v IGN wire source for the LS1 pcm when installing in a 69 camaro? The ign wire I happen to tap into has no voltage while the starter is engaged and thus I couldn't get the engine to fire. I bypassed by giving that wire 12v when I was starting and it fired right off. I have a painless wiring harness connected to stock switches etc.
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post #2 of 7 (permalink) Old May 4th, 16, 01:12 PM
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Re: 12v IGN source thats hot during crank?

Check out Jeff's (user name:24/7) thread. Great info in this thread. Here is just one post (copied and pasted) that may help.




Purple ignition wire to trunk solenoid AND S terminal on starter solenoid.

8 ga from trunk solenoid (same lug as battery) to GMPP load center main post.

Batt cable from trunk solenoid ( switched side ) to starter lug.

Alternator 8 ga to GMPP load center main post.

Stock cabin or AAW fuse box to GMPP load center main post.

GMPP fuse box main post acting as junction for main loads.

Purple ignition wire triggers both trunk solenoid and starter solenoid at same time when key turned to start.

Main battery cable to starter only hot when key turned all the way to start.

8ga from trunk solenoid acts as battery feed and charge wire, be sure to use fusible link as it will be hot all the time.

1969 X66 396 LeMans Blue, M20, 373 (Sold)
1969 Convertible LS3 TKO 600, 373
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post #3 of 7 (permalink) Old May 5th, 16, 05:39 AM
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Al
 
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Re: 12v IGN source thats hot during crank?

The IGN spade on the fuse block for 1969 is (supposed to be) hot when cranking.


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post #4 of 7 (permalink) Old May 5th, 16, 06:14 AM Thread Starter
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Casey
 
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Re: 12v IGN source thats hot during crank?

I wound up going off a pink wire on the ignition switch connector (painless wiring harness) and fusing it for now. I have a couple other connections there but I think the ideal thing will be to add a small fuseblock with a couple relays for the extra devices. This will get me by for now though. I had circuits in the fuse block I'm not using but none of them were hot during crank except the coil circuit which I'm using for the driver side coil packs.
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post #5 of 7 (permalink) Old May 5th, 16, 02:24 PM
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Re: 12v IGN source thats hot during crank?

Casey, what harness/PCM are you using for your swap? Most aftermarket harnesses are 4 wire hookups (Battery, Ignition, Ground and Fuel Pump). Not understanding why you had to wire the drivers side coil packs separately.

Chris
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post #6 of 7 (permalink) Old May 5th, 16, 02:38 PM Thread Starter
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Casey
 
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Re: 12v IGN source thats hot during crank?

Just the factory LS1 F-body engine harness merged with the Painless 18 circuit muscle car harness I installed 10 years ago. I like to wire the items that require 12v ign into two circuits so one will have coil packs and injectors for the pass side, the other will have those for the driver side and the MAF or 12v for trans connector etc.

I'm going to install a 4 circuit add on block with a couple relays as you might find on LT1swap.com to clean things up. Over the years my Painless harness has been messed with a bit and its time to clean-up and document everything. At this point its just good enough to get it running but I'm over that hump now so its time to do it right so I don't have problems later.
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post #7 of 7 (permalink) Old May 5th, 16, 02:57 PM
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Re: 12v IGN source thats hot during crank?

Donny called it!

The start terminal labeled with an "S" on the starter solenoid is hot; powered directly off the battery cable, while the starter motor is engaged.

This goes back to the days of points only getting eight volts from the ignition switch while running and being fed a full twelve volts at start to make for a slightly hotter spark to ease staring the motor.

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