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Ignition issues. Need some help from the Gurus! (1/8)
 7/9/19 7:20pm
somekidwithanm4
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Hi all, I'm Justin

A friend of mine and I had the lucky opportunity to acquire a 1973 Corvette Stingray recently (literally yesterday) and it has been fantastic so far. But now it has one issue.

Today, I pulled it out to give it my full detail treatment. I run and own a detailing company that regularly touches classics and high end exotics, so I'm generally very conservative with the water used on such jobs. After the wash portion it was turned on and pulled into the garage to be dried in preparation for a claybar, paint correction and sealant. After drying off, I went to restart the car, which sputtered for a moment and now is dead as a doorknob. 

After some brief digging, I verified no water entered the distributor and also seemingly none in any of the wires surrounding the area. There was a little that got into the cabin around the windows where they seal to the T-Tops (typical, but nothing crazy). I then verified that we were getting some ignition the the coil. The coil is getting 5.67 Volts with the key in the ignition position and the same when it is cranking. All fuses are dry and intact. Fuel is pumping into the carburetor as it should so there's no issue there. To further verify fueling was not the issues, a small dose of ether was used, but also produced no results. Coil wire was verified to be plugged into the distributor all the way. Next thing I will be checking before i check back here is whether any spark at all is actually making it to the spark plugs which my assumption so far is no. Battery is also new. Any information or tips on where to start would be greatly appreciated!

Here's a picture of the car for fun!

 



|UPDATED|7/9/2019 4:20:32 PM (AZT)|/UPDATED|
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Re: Ignition issues. Need some help from the Gurus! (2/8)
 7/9/19 9:26pm
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


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somekidwithanm4 said:

The coil is getting 5.67 Volts with the key in the ignition position and the same when it is cranking.




There's a problem right there. The ignition coil should be getting full battery voltage(12+ volts) while cranking. The voltage is stepped down only AFTER the key is released from the "Start" position. Try jumping 12v directly to the + side of the coil and crank it...it should fire IF that is the problem. Do not continue to let it run with 12v on the coil...just try it to see if it will fire off and run. If it does, then you have lost the 12v power from the starter solenoid to the coil, which is hot only while cranking. I'd haft to dig the wiring diagram out to be sure, but I THINK it is a yellow wire, connected to the small, outer terminal on the starter solenoid. The actual color isn't that relevant, but it will be attached to the outer terminal. It's possible the fuse-link has burnt on that wire...could be a co-inky-dink, or it may have just gotten a little wet. Try the jumper tick and let us know how that works. 



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Re: Ignition issues. Need some help from the Gurus! (3/8)
 7/9/19 10:58pm
somekidwithanm4
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Adams' Apple said:
somekidwithanm4 said:

The coil is getting 5.67 Volts with the key in the ignition position and the same when it is cranking.




There's a problem right there. The ignition coil should be getting full battery voltage(12+ volts) while cranking. The voltage is stepped down only AFTER the key is released from the "Start" position. Try jumping 12v directly to the + side of the coil and crank it...it should fire IF that is the problem. Do not continue to let it run with 12v on the coil...just try it to see if it will fire off and run. If it does, then you have lost the 12v power from the starter solenoid to the coil, which is hot only while cranking. I'd haft to dig the wiring diagram out to be sure, but I THINK it is a yellow wire, connected to the small, outer terminal on the starter solenoid. The actual color isn't that relevant, but it will be attached to the outer terminal. It's possible the fuse-link has burnt on that wire...could be a co-inky-dink, or it may have just gotten a little wet. Try the jumper tick and let us know how that works. 

Hey Adam, Thanks for responding so quickly.
I grabbed a spare good battery and some primary wire and got the coil wired up with 12 volts. Results sadly ended up the same. No starting with either running on fuel alone or ether. Not even any sputtering. I'm curious if there may be multiple issues going on as the carburetor also seems slightly dry. 

Thank you again for the info as I'm a newer era mechanic which has almost exclusively worked on 90's and 2000's European cars and is fairly inept when it comes to carburetors, mechanical fuel injection and distributors. 

Re: Ignition issues. Need some help from the Gurus! (4/8)
 7/10/19 12:15am
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: 585

Since it won't fire w/ ether, then you must not be getting any spark.  You can check this w/ a clamp-on induction timing lite.

If you rotate the outside mirror 180*, you'll get to see less of the rear fender and more of what's behind you.  🙂



______________

1973 L-82 4 spd

Re: Ignition issues. Need some help from the Gurus! (5/8)
 7/10/19 4:33pm
somekidwithanm4
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Hey Thanks for the responses everyone. 

I finally got it started last night. I swapped out the coil and even though it was hitting 12 volts when cranking, it still wouldn't start. 

What I found is that the auto choke was stuck closed. Again, I have little experience with Carburetors so I didn't think about it until later. So after opening the choke manually and giving it some gas while starting, she fired up in a billow of unburnt fuel. After that the choke remained in it's proper position after several starts. 

This morning, it started just fine. I took it out to the grocery store to test it out further. Drove great. Upon restarting it struggled a tiny bit, but it is 96 degrees today, so that isn't too surprising. On the way home though I noticed at 3/4 and up throttle, it would start misfiring. When I opened up the hood and removed the air cleaner top, I found that the flap for the rear barrels isn't opening under full throttle like I believe it should. Please feel free to correct me if I'm wrong as at this point I'm just hunting for info as to what to adjust.

 

Re: Ignition issues. Need some help from the Gurus! (6/8)
 7/10/19 7:38pm
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: 585

It sounds like you need to check all of the carburetor linkage associated with the choke and the secondary lockout.

FWIW, my experience with small block Chevys is that if it is properly tuned, it will start within one revolution of the crank whether it's hot or cold.



|UPDATED|7/10/2019 4:38:13 PM (AZT)|/UPDATED|


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1973 L-82 4 spd

Re: Ignition issues. Need some help from the Gurus! (7/8)
 7/10/19 8:59pm
somekidwithanm4
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Joined: 7/9/2019
Posts: 4

73shark said:

It sounds like you need to check all of the carburetor linkage associated with the choke and the secondary lockout.

FWIW, my experience with small block Chevys is that if it is properly tuned, it will start within one revolution of the crank whether it's hot or cold.




That's my limited experience as well. Most of the time it's great and starts on one turn. So we'll just begin double checking all linkages. 

Re: Ignition issues. Need some help from the Gurus! (8/8)
 7/10/19 9:43pm
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: 585

On the psgr side of the carb (assuming it is the stock Q-jet) the choke linkage will actuate a secondary lockout unless the choke is completely open.  I assume this is to prevent full throttle blasts before the engine is completely warmed up.  Most of this info is detailed in the factory service manual.  Here's a couple of places where you can find it: https://www.zip-corvette.com/73-shop-service-manual.html

and   https://www.amazon.com/CORVETTE-REPAIR-SERVICE-MANUAL-INCLUDING/dp/B00LTYPFC4/ref=sr_1_12?hvadid=3520538016&hvbmt=bb&hvdev=c&hvqmt=b&keywords=corvette+manual&qid=1562809007&s=gateway&sr=8-12

There are plenty more if you want to search Bing and/or Google.  You can find used ones on ebay that are a lot cheaper.

BTW, the car looks nice in the pic.  How many miles, engine, tranny, options, etc?



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1973 L-82 4 spd