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Engine wont shut off (1/6)
 8/30/18 11:05am
domar5457
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Overland Park, KS - USA

Vette(s):
1980


Joined: 8/30/2018
Posts: 4

Just recently purchased 1980 L48 Corvette. My problem is that once the engine warms up it will continue running with the key in the off position (not dieseling actually running as if the key was still on). Sometimes it will shut down after 10-15 seconds. If I put the trans into reverse the engine immediately shuts down. Added info, previous owner installed an MSD Pro Billet distributor #8551, MSD 6A control module, Accel coil, Edelbrock Performer intake and 750 carb. I greatly appreciate any help in figuring this problem out.
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Re: Engine wont shut off (2/6)
 8/31/18 7:23pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 540

Assuming it's an automatic, I would check the neutral safety switch because it seems like the voltage getting to the ignition system to keep it running has something to do with that switch.

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1973 L-82 4 spd

Re: Engine wont shut off (3/6)
 9/1/18 7:26am
Adams' AppleLifetime Member
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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: 19601

1: Idle too high
2: Vacuum leak
3: MSD module


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Re: Engine wont shut off (4/6)
 9/1/18 9:36am
domar5457
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Overland Park, KS - USA

Vette(s):
1980


Joined: 8/30/2018
Posts: 4

Thanks for the response 73shark. I will look into the neutral safety switch. Is there a test that can be performed to determine if it is functioning correctly? 
I have also read in the MSD literature that the control module can possibly bleed by current as well. I don't particularly like the MSD system and will more than likely switch back to an HEI system.
Re: Engine wont shut off (5/6)
 9/1/18 9:45am
domar5457
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Overland Park, KS - USA

Vette(s):
1980


Joined: 8/30/2018
Posts: 4

Thanks for reply Adams Apple. Prior to addressing this issue I had to address the headlight doors not functioning properly. I have been through the vacuum system like crazy as I am sure a lot of C3 owners have. I was able to get them working correctly. It doesn't hurt to revisit this though you never know. As I responded to 73shark, I did pull up literature on the MSD system and found that there can be bleed by of current through it. I will more than likely convert back to HEI. The MSD system is overkill for this motor and it adds more equipment under the hood.

|UPDATED|9/1/2018 6:45:02 AM (AZT)|/UPDATED|
Re: Engine wont shut off (6/6)
 9/1/18 4:28pm
73shark
Standard Member
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 540

I agree that the first place to look would be the possibility of a fast idle allowing run-on with no ignition. Also the HEI system probably provides a hot or hotter spark than the MSD system does. I remember reading when they were developing the HEI system that they actually had to dial back the spark output voltage because they couldn't get good enough insulation on the wires to a stand it.

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1973 L-82 4 spd