Carb LS3 (LS376 / 515) Will Not Shut Off - Team Camaro Tech
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post #1 of 50 (permalink) Old Sep 30th, 18, 04:23 PM Thread Starter
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Carb LS3 (LS376 / 515) Will Not Shut Off

LS3 engine installed in a '68 Camaro with an American Autowire classic update wire harness. I'm using an internal regulator Corvette alternator and I installed a Holley diode pigtail that is connected to a 12 volt switch wire that powers the tach gauge. In order to shut off the engine I have to turn off the fuel pump. Any ideas?
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post #2 of 50 (permalink) Old Sep 30th, 18, 04:41 PM
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

What are you using for ECU?

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post #3 of 50 (permalink) Old Sep 30th, 18, 04:43 PM
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

When you turn the key off it should open the ignition relay and shut the engine off

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post #4 of 50 (permalink) Old Sep 30th, 18, 05:04 PM
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

Quote:
Originally Posted by jigoe007 View Post
LS3 engine installed in a '68 Camaro with an American Autowire classic update wire harness. I'm using an internal regulator Corvette alternator and I installed a Holley diode pigtail that is connected to a 12 volt switch wire that powers the tach gauge. In order to shut off the engine I have to turn off the fuel pump. Any ideas?
Are you using the MSD 6014 controller ?

I'm using the Holley red low pressure fuel pump that's wired to the ignition switch. It doesn't really require a relay.

You didn't wire the pump to your ignition switch ?

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post #5 of 50 (permalink) Old Sep 30th, 18, 05:14 PM Thread Starter
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

I'm using a GM LSX Ignition Controller mounted to the Edelbrock intake manifold. I have an Edelbrock fuel pump with a dedicated stand alone switch. The fuel pump is working fine. I'll have to check out the ignition relay.
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post #6 of 50 (permalink) Old Sep 30th, 18, 05:29 PM
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

Would be useful if you posted a wiring diagram including the diodes and relays etc you have used.

Don

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post #7 of 50 (permalink) Old Oct 6th, 18, 10:23 AM Thread Starter
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

I tested the relay and it appears to be working fine. I applied 12v to it and it clicked shut. Also while applying 12v I checked the continuity across the other terminals and the multimeter buzzed so I'm getting a complete circuit there. Again the engine starts and runs fine. The pink wire from the LSx controller is connected to the pink ignition switch wire. While the engine was running and with the ignition switch in the off position I had 0.6v at the pink ignition wire at the ignition switch so there shouldn't be power at the pink LSx controller wire when I turn the key off. While the engine was running I disconnected the three wire (pink- 12v power, yellow- tach signal, brown- ground) connector from the LSx controller and the engine stopped immediately while the key was in the run position.

Does this mean the ignition switch may be bad (new from American Autowire) but I'm getting 0.6v at the pink wire at the ignition switch in the off position. As a band-aid fix which I really don't want to do I guess I could install a switch just for the pink wire which would kill the power to the LSx controller.

Last edited by jigoe007; Oct 6th, 18 at 10:39 AM.
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post #8 of 50 (permalink) Old Oct 6th, 18, 11:14 AM
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

Quote:
Originally Posted by dhutton View Post
Would be useful if you posted a wiring diagram including the diodes and relays etc you have used.

Don

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post #9 of 50 (permalink) Old Oct 6th, 18, 05:21 PM
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

If the ignition relay opens when you turn the switch to the off position the engine WILL shut off if wires correctly.

Don Xs 2. Show is your wiring diagram.

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post #10 of 50 (permalink) Old Oct 6th, 18, 06:04 PM Thread Starter
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

This diagram shows the trunk battery arrangement and the relay connections.
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post #11 of 50 (permalink) Old Oct 6th, 18, 06:22 PM Thread Starter
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

Looks like I can't upload any more drawings. The "START" wire is the purple starter solenoid wire coming from the ignition switch which is spliced to the blue wire from remote trunk solenoid. That connects to terminal 86 of the relay. The terminal block which is mounted to the firewall, is not shown on the diagram, has 4 wires attached: the 8 gauge red wire from the trunk, red wire (American Autowire) from the alternator output, one wire for two radiator fans and fusible link dash main power wire.

The alternator has the one diode wire that connected to switched 12v near the dash.

Last edited by jigoe007; Oct 6th, 18 at 06:43 PM.
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post #12 of 50 (permalink) Old Oct 6th, 18, 06:42 PM
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

Quote:
Originally Posted by jigoe007 View Post
This diagram shows the trunk battery arrangement and the relay connections.
At the risk of getting spanked by SOA-Nova what is the purpose of that relay? It is redundant imho. Is there some kind of fear that the ignition switch cannot supply enough current to the starter solenoid yet for some reason can drive the trunk mounted solenoid?

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post #13 of 50 (permalink) Old Oct 6th, 18, 06:49 PM
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

What is the purpose of the diode wire? Where on the alternator is it connected?

What switches the switched 12volt that you connected the diode wire to? What is the polarity of the diode wire?

Don

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post #14 of 50 (permalink) Old Oct 6th, 18, 07:01 PM Thread Starter
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

That setup is from MAD Electrical who are big on relays. I also have a horn relay and two relays for the radiator fans. Yes, I think the idea is to help prevent overloading of the ignition switch. I'm a novice at best at this.
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post #15 of 50 (permalink) Old Oct 6th, 18, 07:15 PM Thread Starter
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Re: Carb LS3 (LS376 / 515) Will Not Shut Off

The diode wire is Holley part 197-400. I don't know the polarity of the diode. I guess it could be faulty. It came from Holley already assembled. I have a "one wire" alternator so it's my understanding I needed to use the diode wire since there's no exciter wire. It connects at the top of the alternator which has 3 pins. The wire only has one pin. I researched this online last year but it obviously did not solve the problem of the engine not stopping. The switched 12v is coming off the ignition switch. The actual wire is the 12v switched power to the tach.
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