Car Doesn't Turn Off Unless...
Thread Starter
7th Gear
Joined: Aug 2008
Posts: 7
Likes: 0
Car Doesn't Turn Off Unless...
Man I'm shooting blanks recently... Anyway we just finished installing a Power Master 100 AMP ALT which went perfect. Started the 77 350 right up. Let it idle to about 150F and decided to turn it off, but it wouldn't turn off.. Car kept running - ALT gauge was pinned at 14. Around 190F our dual electric fans came on and the ALT gauge dropped to 13 so we decided to try turning it off again and now the car finally turned off. We tried this several times and the only way for the car to turn off is by dropping the volts down to 13 aka allowing the fans to come on. Seems to be a bad solenoid in the MSD 6A box... I can't think of anything else.. Any other ideas guys?
Can't be the key ignition since we've had the car for over a year w/o any of these issues... Man I can't win these days.. Can't think of anything else except for the MSD box... What else would control / care about the current in this case...
Thanks in advance!!!
Bry H
P.S. Durango_Boy - went in perfect.. Thanks!!!
Can't be the key ignition since we've had the car for over a year w/o any of these issues... Man I can't win these days.. Can't think of anything else except for the MSD box... What else would control / care about the current in this case...
Thanks in advance!!!
Bry H
P.S. Durango_Boy - went in perfect.. Thanks!!!
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
You're welcome.
Ironically as I was reading the title and the first part of your symptoms I was already thinking that my first question would be if you had an MSD ignition system.
It's hard to search right now with the forum getting updated, but it seems the last few people that had this run on problem were all using an MSD box and a sticky relay was the problem.
Ironically as I was reading the title and the first part of your symptoms I was already thinking that my first question would be if you had an MSD ignition system.
It's hard to search right now with the forum getting updated, but it seems the last few people that had this run on problem were all using an MSD box and a sticky relay was the problem.
Instructor
Joined: Jun 2008
Posts: 105
Likes: 0
ya it might be a bad solenoid but bad solenoid stop work when they get hot so i wonder why it works when it get hot. My guess is your getting some voltage bleed back. I might try to throw a diode on it and see what happens
Safety Car
Joined: Oct 2007
Posts: 3,729
Likes: 267
From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
1. either your backfeeding power from your alternator , to your Igintion system,
you will need to install a diode(Ithink to prevent this).
or
2. you did Not wired your MSD box to switched off Iginition source.
god luck... 69VETT
you will need to install a diode(Ithink to prevent this).
or
2. you did Not wired your MSD box to switched off Iginition source.
god luck... 69VETT
Drifting
Joined: Oct 2007
Posts: 1,317
Likes: 22
From: Marina CA
I had this happen on another vehicle with an electric fan setup. when the power was cut the fan would backfeed into the system as a mini alternator. The cure was a diode on the feed line to the fan to prevent a backfeed into the electrical system.
Thread Starter
7th Gear
Joined: Aug 2008
Posts: 7
Likes: 0
99.99% certain I figured it out... The original guy never installed the 100V 1A diode inline to the light cable aka brown wire... So we're getting run on or current to back flow into the system keeping it running...
Going to install one tomorrow and keeping my fingers crossed that's the issue... Thought that would already installed inline but I thought wrong...
Thanx guys!!!
Bry H
Going to install one tomorrow and keeping my fingers crossed that's the issue... Thought that would already installed inline but I thought wrong...
Thanx guys!!!
Bry H
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
99.99% certain I figured it out... The original guy never installed the 100V 1A diode inline to the light cable aka brown wire... So we're getting run on or current to back flow into the system keeping it running...
Going to install one tomorrow and keeping my fingers crossed that's the issue... Thought that would already installed inline but I thought wrong...
Thanx guys!!!
Bry H
Going to install one tomorrow and keeping my fingers crossed that's the issue... Thought that would already installed inline but I thought wrong...
Thanx guys!!!
Bry H
I don't think it's a diode that goes inline with the brown wire. It needs to be a resistor. The premise is that the diode acts as a light, like a GEN light, telling if there is a drop in voltage on either side. If a diode was placed there instead of a resistor, it would be a one way street and I don't know that it would charge that way. Now, it'll need the resistor for sure, but I'm not so sure the diode is a good idea.
Someone better with electronics will chime in.
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Thread Starter
7th Gear
Joined: Aug 2008
Posts: 7
Likes: 0
Durango_Boy; you're obviously a smart guy but today you're wrong. Well at least basing it off of MSD's instructions. You've been a huge help yesterday and I thank you again! Knew I was getting some type of voltage "blow back" and knew I hooked up everything right... My buddy who drags a 856HP 68 Stang told me it's the diode for the MSD box. So I had to take a look and found this:
http://www.msdignition.com/uploadedF...structions.pdf
Go to page 8 = Engine Run-On... Install 100V/1A Diode inline to the lamp lead aka Brown Wire...
Thanks!
Bry H
http://www.msdignition.com/uploadedF...structions.pdf
Go to page 8 = Engine Run-On... Install 100V/1A Diode inline to the lamp lead aka Brown Wire...
Thanks!
Bry H