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6/18/17 10:08am - Original Message: 'Funny starting'
Ronnie71
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Smethport, PA - USA

Vette(s):
1971 T Top <1year

Joined: 5/27/2014
Posts: 13
1971 350/270.  Since I installed a HEI ignition system the engine will only start when the key is released from the start position.  I have 12v to the distributor from the IGN post on the fuse block. The battery spins the engine well buts drops to about 10 volts when cranking. Is this normal? I suspect I'm getting a voltage drop during cranking.  How do I troubleshoot this.  Thanks for your help.

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6/18/17 9:18pm - Reply: 'Re: Funny starting'
stingrayjim jr Lifetime Member
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SHELBYVILLE, TN - USA

Vette(s):
1976 L48 auto

1978 L82 4speed

1994 LT1 6speed

Joined: 7/5/2002
Posts: 3937
10 volts while cranking the starter isn't too bad, might be just a touch on the weak side, but it should still be enough voltage to work the ignition coil.  Voltage drop below 10.5 can be a sign of a battery starting to go... if you have access to another battery, or maybe a jump box/or jumper cables,  it might be worth a try to see if that helps the situation... As for the engine not wanting to start untill the key is released, that's kinda odd.... just for the fun of it, take the hot wire off the coil and put a volt meter on it and then turn the key to turn over the engine and see if there is voltage there, if the voltage there is considerably lower(under 9 volts) it may not have enough to fire the coil.... hopefully, someone else will have an idea of whats going on here.... of course the common answer to most electrical issues on vette's is a grounding problem...but not sure here...

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StingrayJim
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Stingray's '76                             StingrayJr's '78                           Lil Red '94

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6/19/17 12:45pm - Reply: 'Re: Funny starting'
Ronnie71
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Smethport, PA - USA

Vette(s):
1971 T Top <1year

Joined: 5/27/2014
Posts: 13
Stingrayjim, Thanks for the comeback. Tried the jumper box with no change so the battery is not the problem. Looks like there is a power drop, (0 volts) at the primary ign wire to the distributor when the key is in the start position. I also note that I don't have any power to the radio etc when the switch is in the ACC position so I'm starting to think ign switch.  What do you all think?  What should I be checking next?

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6/19/17 3:32pm - Reply: 'Re: Funny starting'
stingrayjim jr Lifetime Member
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SHELBYVILLE, TN - USA

Vette(s):
1976 L48 auto

1978 L82 4speed

1994 LT1 6speed

Joined: 7/5/2002
Posts: 3937
ok, trying to look at some wiring diagrams for your year model, and not sure how you ran the hot wire for the HEI, however, the original wire was tapped off the starter solenoid, so i would assume(yeah i know, not the greatest thing to do) that the hot wire to the coil is a direct feed from the battery.  As most of us notice whenever we start a vehicle, when turning over the engine all the other electronics seem to go dead, or nearly dead until the engine starts.  This is usually a result of the power draw the starter pulls,  and seems that is happening here if you have zero volts at that wire when turning the starter....    so, logic would dictate that we need to find a wire that is hot while cranking the motor..  :)  

as for the radio....i donno... :)  does it work with the key in the run position??  if so, then possible that the key switch is the culprit... contacts worn/corroded/broke/etc.. 


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StingrayJim
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Stingray's '76                             StingrayJr's '78                           Lil Red '94

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6/19/17 4:27pm - Reply: 'Re: Funny starting'
Ronnie71
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Smethport, PA - USA

Vette(s):
1971 T Top <1year

Joined: 5/27/2014
Posts: 13
OK.  I'm getting my 12v to the coil from the fuse block.  With the hot wire disconnected from the distributor I've got 12v with the key in the run position and zero v in the start position with no draw on the circuit.  It appears either the key lock switch or main switch at the base of column has failed.  I'm not sure how to check them without just changing them out.  My radio works when the key is in the run position so it looks like the ACC circuit has failed as well.  How do I narrow it down to the fail.ed switch?  I also just read on another forum that a bad starter solenoid can cause the same symptoms. Thanks again.

|UPDATED|6/19/2017 2:27:52 PM (AZT)|/UPDATED|


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6/26/17 9:01pm - Reply: 'Re: Funny starting'
stingrayjim jr Lifetime Member
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SHELBYVILLE, TN - USA

Vette(s):
1976 L48 auto

1978 L82 4speed

1994 LT1 6speed

Joined: 7/5/2002
Posts: 3937
ok, didn't think about the solenoid itself...it could be the gremlin here.... it should have a wire or wires that feed off there that stay 'hot' when cranking the engine, providing the voltage to the coil... it appears that its spliced(looking at a wiring diagram) with another wire that is probably 'hot' with key on, and then 'cold' with key off killing the ignition in order to stop the engine...  you might duck under the car and check the wiring off the solenoid(sounds easy i know, i cant fit my butt underneath a vette without jacking it up)... 

most solenoids have the terminals labeled "I" and "S"... "I" for Ignition, and "S" for start... the "I" terminal should have 12volts when the engine is being started(turning over) but zero volts when the key is in 'run'.... therefore, the splice in the wiring diagram to supply 12 volts to the coil in the key position "run" and "start"... :)

you really need to get yourself a wiring diagram,  they look intimidating but once you stare at it and notice the colors of the wires you can grasp onto the concept  of how they are laid out in the diagram...hardest part is when the wire goes off one page and onto another, trying to find the right wire on page 2.....   



Wiring Diagram


(large diagram modified to link-aapple)


|UPDATED|6/26/2017 7:01:50 PM (AZT)|/UPDATED|


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StingrayJim
NCM Lifetime Member #1936

Stingray's '76                             StingrayJr's '78                           Lil Red '94

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6/19/17 8:01pm - Reply: 'Re: Funny starting'
Ronnie71
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Smethport, PA - USA

Vette(s):
1971 T Top <1year

Joined: 5/27/2014
Posts: 13
I'll test the solenoid tomorrow, if its not that then its either a broken wire,  faulty key interlock or ignition switch.  Thanks for the diagram.  I'll let you know what I find.

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6/21/17 4:16pm - Reply: 'Re: Funny starting'
Ronnie71
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Smethport, PA - USA

Vette(s):
1971 T Top <1year

Joined: 5/27/2014
Posts: 13
The starter solenoid checks out.  Going to replace the ignition switch next.

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6/26/17 9:04pm - Reply: 'Re: Funny starting'
stingrayjim jr Lifetime Member
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SHELBYVILLE, TN - USA

Vette(s):
1976 L48 auto

1978 L82 4speed

1994 LT1 6speed

Joined: 7/5/2002
Posts: 3937
Ummm, before getting into the ignition switch,  double check the wires I circled in red on the schematic.... you'll see one coming off the solenoid, the other splicing into it just at the coil....  the one splicing in from the firewall(key switch) is hot when the key is on, the other wire coming off the solenoid is hot when you turn the motor over....so if the solenoid is good, there will be 12 volts when you activate the solenoid(turning the engine over) then the other wire is hot when the switch is in RUN position....  if the wire is hot(12 volts) with the key on, then more than likely the key switch is ok, in this instance....    might check the wire at the solenoid with key in Run and see if 12 volts is read at the wire there.... basically checking to see if its a broken wire....  


Modified diagram

(large diagram modified to link-aapple)





|UPDATED|6/26/2017 7:04:53 PM (AZT)|/UPDATED|


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StingrayJim
NCM Lifetime Member #1936

Stingray's '76                             StingrayJr's '78                           Lil Red '94

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6/25/17 7:48pm - Reply: 'Re: Funny starting'
Ronnie71
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Smethport, PA - USA

Vette(s):
1971 T Top <1year

Joined: 5/27/2014
Posts: 13
Thanks.  I have 12 volts on the wire to the coil in the run position and 12v at the solenoid "s" terminal when the key is in the start position.  I'm pretty sure it's a bad ignition switch. I've got a new switch but changing it will require dropping the steering column so I'm waiting for a rainy day to take this on.

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6/25/17 10:32pm - Reply: 'Re: Funny starting'
stingrayjim jr Lifetime Member
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SHELBYVILLE, TN - USA

Vette(s):
1976 L48 auto

1978 L82 4speed

1994 LT1 6speed

Joined: 7/5/2002
Posts: 3937
then,if you have 12 volts with the key in start at the S terminal, the wire going back up to the distributor is probably broken.... the wire coming off the solenoid is tied into the hot wire coming off the fuse block that goes to the distributor.... so there is a constant 12 volts going.  

Unless I am mis-understanding something here, it sounds more like the wire coming off the solenoid going to the dist that has issues.... broken wire or bad crimp on the end..... if the key switch works turning over the engine, then i would think its good...



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StingrayJim
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Stingray's '76                             StingrayJr's '78                           Lil Red '94

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6/26/17 9:23pm - Reply: 'Re: Funny starting'
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19458
This being a '71 car, the original coil power from the ignition switch will be a resistor wire, which will drop the voltage from 12v down to about 8-9v...not enough to operate the coil on an HEI set-up. In order to have voltage to start the engine at the coil while cranking, it uses a full battery voltage(12v) source from the starter solenoid "I" terminal, which is the outside terminal of the solenoid.

Any terminal on the fusebox marked "Ign" will ONLY be hot with the key in the "Run" position, so there will be no voltage on that terminal while cranking. It starts when you release the key because voltage is now on that terminal.
You should, as Jimmie points out, and you confirmed, have 12v on the wire coming from the "I" terminal on the solenoid while cranking ONLY. In order for your set-up to work properly, you need to have BOTH wires, "I" from starter solenoid AND the wire from "IGN" terminal on fusebox connected on the "Batt" terminal of the HEI coil/dist cap. This will give you 12v while cranking(from the solenoid) and 12v in the "Run" position(from the fusebox).
Your ignition switch is not causing the problem, since you do have 12v on the "Ign" terminal with the key on.
hth  Thumbs Up



The "S" terminal at the solenoid is 12v coming from the ign switch to CRANK the engine...there will be NO voltage on that terminal in any key position EXCEPT while cranking. The "S" terminal is the small terminal closest to the engine block, and will be a larger diameter purple wire.


|UPDATED|6/26/2017 7:23:31 PM (AZT)|/UPDATED|


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Joel Adams
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6/27/17 1:55am - Reply: 'Re: Funny starting'
stingrayjim jr Lifetime Member
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SHELBYVILLE, TN - USA

Vette(s):
1976 L48 auto

1978 L82 4speed

1994 LT1 6speed

Joined: 7/5/2002
Posts: 3937
Ooops, forgot about there being a resistor..... ok, must admit, i didn't realize there was a resistor.   Although he was getting 0 volts while its turning over makes me think the wire is either broken, or if there is a resistor, it might be disconnected or blown....guess if it were me and could not trace the wire, i would be compelled to run a hot wire to a momentary switch and splice it into the hot wire off the key switch... yeah i know,  me bubba...you jane... :)  but then i could at least drive and pick up a milkshake ... or banana split... onion rings... great, i'm hungry now... 

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StingrayJim
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Stingray's '76                             StingrayJr's '78                           Lil Red '94

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6/27/17 7:59am - Reply: 'Re: Funny starting'
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19458
It's all in the details, Jimmie. Thumbs Up
In the original post, he states that he has 12v to the HEI from an "Ign" terminal on the fusebox, so that means he is not using the original resistor wire for the coil feed, but has run another wire from the fusebox to the distributor....at least that's how I read it. As I pointed out, the "Ign" terminals) on the fusebox are only hot with the key in the "On" or "Run" position....not while cranking. Also, the label "Ign" on the fusebox doesn't mean those terminals are for the ignition system, but simply meant to say that those terminals are only hot with the ignition switch ON....otherwise they are dead, power-wise. He will need to have the two wires (from "I" on solenoid and "Ign" on fusebox) tied together somewhere to make this work. Both wires will not be hot at the same time, so no issues there with backfeed.
The only other way to make it work is to find a terminal on the fusebox that is hot in both "Run" and "crank" modes.....which would have to be something in the lighting, or horn circuits. Smile



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Joel Adams
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6/30/17 7:29am - Reply: 'Re: Funny starting'
nosal1 Gold Member
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Dunedin, FL - USA

Vette(s):
1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.

Joined: 3/21/2006
Posts: 238

Good Morning It sounds like you still have the 8' ressister wire in service that was used for a points system relative to OEM points system.You will have to run a separate 12 gauge RED wire from IGN post on fuse block to BAT side of HEI distributor.If you still have a yellow wire then disconnect this as it will go down to the R side of solinoid and will not be needed. God Luck      nosal



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7/1/17 7:15pm - Reply: 'Re: Funny starting'
Ronnie71
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Smethport, PA - USA

Vette(s):
1971 T Top <1year

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Posts: 13
Oh man! I should have checked the blog this am BEFORE I dropped the steering column and installed a new ignition switch which, as Adam explained, is not the issue.  Thanks for clearing up the fact that I need to patch a wire to the "I" terminal to get 12v to the distributor in "start". At least I now know how to change out my steering column....maybe I should upgrade to a T&T while I'm at it. :-)

update:  patched a jumper wire between the "I" terminal on the starter solenoid and battery input wire to the coil/distributor.  Started on the first roll!  Problem solved!  Now to put it all back together.  Thanks everyone for your help.  C3VR is awesome!!


|UPDATED|7/1/2017 5:15:28 PM (AZT)|/UPDATED|


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7/2/17 9:52am - Reply: 'Re: Funny starting'
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

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Glad to hear ya got it goin!!


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Joel Adams
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7/2/17 4:44pm - Reply: 'Re: Funny starting'
stingrayjim jr Lifetime Member
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SHELBYVILLE, TN - USA

Vette(s):
1976 L48 auto

1978 L82 4speed

1994 LT1 6speed

Joined: 7/5/2002
Posts: 3937
yippee!!  :)  

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StingrayJim
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Stingray's '76                             StingrayJr's '78                           Lil Red '94

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