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#1 |
Registered User
Join Date: Apr 2017
Location: Hammond, La.
Posts: 51
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Engine still runs with key turned off
So I finally have my truck back together and just installed a painless harness. Everything seams to be working fine except when I turn the key to the off position the engine doesn't kill. Been reading a few articles and some say that the alternator could be back feeding the ignition switch. Does that sound right or has anyone else had or even heard of this problem? I installed a later model alt with the internal regulator to avoid more wiring and a cleaner look under the hood. I don't know if that matters. Thanks in advance.
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#2 |
Registered User
Join Date: Oct 2012
Location: Greenville, Oh
Posts: 72
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Re: Engine still runs with key turned off
Does the truck not shut off at all or does it shut off after a few seconds?
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#3 |
Who Changed This?
![]() Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,394
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Re: Engine still runs with key turned off
Make sure that the yellow wire going to the "R" terminal on the starter isn't touching the hot battery cable on the solenoid.
__________________
~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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#4 |
Registered User
Join Date: May 2016
Location: Henderson NC
Posts: 975
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Re: Engine still runs with key turned off
How is your alternator wired? There are several threads on here that show the proper way to switch to an internal regulator alternator.
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#5 |
Registered User
Join Date: Aug 2015
Location: Alcoa;Tn
Posts: 208
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Re: Engine still runs with key turned off
Have you installed a electrical fan on your truck? Sometimes they will backfeed till the fan slowes down and stop turning.
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'71 Cheyenne Super LWB - Second Owner in 39 Years! '70 CST/10 SWB - Soon to be Daughter's truck when finished |
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#6 |
Registered User
Join Date: Aug 2014
Location: Mena,Arkansas
Posts: 485
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Re: Engine still runs with key turned off
I would look in to how the alternator is wired also. I wade this mistake on a rewire and had the same result.
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68' with no bells or whistles unless I add'em. |
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#7 |
Registered User
![]() Join Date: Nov 2012
Location: canby,oregon
Posts: 350
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Re: Engine still runs with key turned off
X3 on the alternator being wired backwards.
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#8 |
Senior Member
![]() Join Date: Nov 2014
Location: Colorado
Posts: 3,221
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Re: Engine still runs with key turned off
You might also check the wiring on the back of your ignition switch. We had a Blazer with lots of stereo equipment and they had the purple wire pushed in to the wrong place and it did the same thing.
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07' Extcab Silverado Z71 Silver Birch, 5.3L HO 71' Cheyenne C10 Hugger Orange on Saddle SWB Besides these two, too Many to count |
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#9 |
Registered User
![]() Join Date: Feb 2012
Location: Vinton, Va.
Posts: 473
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Re: Engine still runs with key turned off
I doubt this is your problem but replacing the points with a pertronix modual will sometimes cause it not to turn off. A specific diode solves that issue. Just some useful info.
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"You are not forgotten" USMC 75-79 (Aviation Ordnance Tech- F-4 Phantom) 1959 H-D Panhead. Owned since 1978. Currently with son in Lawton, OK. 1968 Chevy Custom SWB pick up. Fleetside. Lowered 4/6. Totally refurbished. 1966 Pontiac GTO. 4 speed. Saved original 389. Now has slightly built 455 engine. 355 rear gears. Very fun to drive ! |
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#10 |
Registered User
Join Date: Apr 2017
Location: Hammond, La.
Posts: 51
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Re: Engine still runs with key turned off
Truck does not shut off at all (not dieseling). I don't have anything hooked up except for ignition stuff to run the motor. no radio, fans, lights, etc. I doubt the wiring to the alt is backwards cause the harness is clearly labeled but I am def going to double check. I will research the internal alternator swap thread and see if that sheds some light on my situation. I will get some pics this evening and post. thanks again. love the input from this forum!
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#11 |
Registered User
Join Date: Sep 2015
Location: portland, OR
Posts: 48
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Re: Engine still runs with key turned off
This is a common problem. Put a dummy light inline (any little interior bulb would work for test) on the wire to the alternator terminal #1, right near the alternator. The bulb is just acting like a little resistor. This test will point you to the problem. If it works, there are countless websites showing how to properly diagnose and wire the alternator correctly.
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#12 |
Registered User
Join Date: Apr 2017
Location: Hammond, La.
Posts: 51
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Re: Engine still runs with key turned off
Sounds pretty common. I'll get after it this evening and see if I can figure it out. but I might have to take it around the block first for its maiden voyage
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#13 |
Registered User
Join Date: Aug 2014
Location: Mena,Arkansas
Posts: 485
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Re: Engine still runs with key turned off
Round the block is a great idea. Might just have to do the same with mine!
__________________
68' with no bells or whistles unless I add'em. |
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#14 |
Registered User
Join Date: Apr 2017
Location: Hammond, La.
Posts: 51
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Re: Engine still runs with key turned off
After some trial and error I installed a external regulator from my parts pile and it solved the problem. And took it around the block for the first time! hope the pics come out right been a while since I posted anything.
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#15 |
Msgt USAF Ret
![]() ![]() Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,714
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Re: Engine still runs with key turned off
Have you thought about just unplugging the alternator to see if it'd shut off. If it doesn't then maybe the key switch is the problem.
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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#16 |
Registered User
Join Date: Apr 2017
Location: Hammond, La.
Posts: 51
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Re: Engine still runs with key turned off
Yea I tested that too Vet. Unpluged the alt after I turn the key to off position and it dies.
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#17 | |
Msgt USAF Ret
![]() ![]() Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,714
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Re: Engine still runs with key turned off
Quote:
It also provides enough resistance to prevent the backfeed to the ignition switch which will cause the engine run on. If you don't have a charging light as with the gauge cluster, you have, or should have a resistance wire running from the key switch to the inside of the cab at the firewall block. It connects to the no.1 alternator wire which excites the alternator. Bottom line: install a small diode in the no.1 wire which should cure the problem, but be sure it is installed so that the current will flow to the alternator. This symbol I<- is on the diode and the arrow must point toward the alternator. A small 1 watt diode should be fine.
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. Last edited by VetteVet; 06-21-2018 at 11:51 AM. |
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#18 |
Msgt USAF Ret
![]() ![]() Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,714
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Re: Engine still runs with key turned off
By the way that regulator you installed is for a generator so I don't know how it worked.
How were you able to wire it to the SI alternator?
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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