Finally got my SBC conv started, won't turn off though

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thebigredrocker

thebigredrocker

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Stock harness to a 1969 sbc with Coil pack HEI dizzy. Starts great but the ignition switch won't turn it off. Couldn't find the thread, know it's been covered.

I did a test with the ignition wire to the Alternator unplugged, it will turn of using the ignition switch that way. I am getting feedback through the line correct? Is there another hot on ACC wire I can use? Or do I need some sort of diode in the line?
 
Are you running a Toyota or SBC alternator?

Your alternator is providing power to the coil +. If it's wired to a separate circuit it wouldn't do that.
 
Forgot to mention what Alternator. It's a Delco Remy GM Alternator with the two wire plastic plug and one big hot lug that is hot all the time. Sound like I need a dummy light, diode or one wire kit. Thanks for the help fellas.
 
i just converted the e-brake light into the dummy light . the ebrake light never functioned for me anyways .
so the oem brake light came in handy and no mod to the dash .
delco remy 3 wire for me also

the one wire kit is just a conversion you open up the alt and change the regulator to a self exiting one .
regulator is the plastic thing with two prongs .lol


http://www.ebay.com/itm/ONE-1-WIRE-...ING-/371221277720?hash=item566e832c18&vxp=mtr



.
 
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I found this info (P.S. - clicking on the link will begin a PDF download. The info is on page 10 & 11.) on MSD site and believe it will resolve your problem. I've been living with the same issue for years. My solution was to put a switch in the line feeding the coil power and if the engine wouldn't stop I'd simply flip the switch which opened the circuit. It also served a second function as an anti-theft device. I'll be adding the diode to my setup but will also keep my switch.
 
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Well I went down to my local Radio Shack today and picked up a couple of the diodes (2 to a package) for under $2.

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The specifications indicate they are 1 amp 400 volt micro rectifier diode. I'm hoping the "micro" doesn't hinder or cause failure prematurely. They do appear about half the size of what I was expecting.

Instead of soldering them into the wire I decided to crimp them in place. I stripped the blue plastic off a couple of butt connectors. Instead of cutting the leads shorter I threaded them through the butt connector and put a slight bend where it exited the connector. I then removed the connector and bent back the lead 180 degrees. After cutting and stripping the wire, which by the way appeared to be molded right to the wire, it was slip on some 1/4" heat shrink and then crimp things together. I only crimped the end with the wire leaving the diode room in that end of the butt connector to have some wiggle room.

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Up came the heat shrink followed by some heat and job about done.

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I'd slipped the connectors out of the plastic housing to make things easier to work on. So, before going back together I cleaned up the contact surfaces and put dielectric grease on everything to keep air and moisture out for longer life.

I can't say with 100% certainty that this is going to cure the run on issue because it may be a couple of weeks before I fire the motor. However, when I was doing some work with the fuse block and finishing up some electrical work on recent additions I did measure some minor power feeding back on some fuse connections. I'm not good with electrical so you'll have to bare with me as I try and explain. While looking for hot and switched fuses with the meter set for 20 volts, hot connections were showing 12+ volts while certain others were reading like 0.05 volts when I was expecting to see 0. After adding in the diode today I checked the engine fuse which I know is switched and with the key off it was showing 0 today. My assumption is that the small wire from the alternator was allowing a very minor voltage feedback and the diode has now stopped it.

I'll let you know for certain once I fire the motor.
 
I couldn't find a consensus on IH8MUD or out in the Chevy forums, so I cheated and bought this from Speedway Motors:

http://www.speedwaymotors.com/Alternator-Wiring-Harness,2373.html

Comes with the diode installed. I cut the ring off the sense terminal and ran it all the way over to the battery instead of "cheating" it back over to the +BAT line like it's set up to do.

This setup works great for me. I also bypassed the main harness and amp meter while I was in there - the stock amp meter is set up to work with the original 50-60A Toyota alternators...the 12SI pushes 97A and I didn't want to risk blowing it.
 
Well today I fired up the motor for the first time after installing new EFI and exhaust. You can see a short video here. Anyway the diode that I added worked like a charm. The motor started fine and alternator showed normal charging and the important part was that when I turned off the key the motor stopped running, every single time!

Now the switch that I installed initially is truly just an anti-theft device as it is not needed any longer to kill the motor. :)
 
Well, I am getting closer. I have the Speedway motors alternator pigtail with the diode. I haven't tested it yet. Been focused on getting my steering ready. I bought a welder, taught myself to weld watching youtube, got my Saginaw conversion bracket welded up as well as some mounts for a really beefy 4x4Labs bumper. Got everything cut, welded, painted and ready to install. I am going with 4x4Labs Frombe steering, so I had to get all that stuff painted too. Got my junkyard Saginaw torn apart(it was caked in fluid), painted it with the dark grey Por-15 Manifold paint, baked it in the oven last night. Should have all the seals for the rebuild tomorow. Then I'm going to attempt to hook up all the steering stuff, mount radiator, wire up the electric fan, and permanently wire up everything else. I guess if the Speedway diode doesn't work I'll tear into my Alternator and install a new rectifier bridge with diode. I am inching closer.
 
Boys I got bad news. Stabbed myself in the leg with a sharp knife. Not fun. I'll add my alternator ain't even hooked up and mine does this with just the starter motor which when cranked won't stop! I have to pull the pos cable! So my ignition won't spring back from position 4 after crank? Fix or replace entire steering colum and be done with it!?
 
I'm not walking well.
 
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