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Topic: 71 no sparky spark

71 no sparky spark (1/2)
 5/21/20 12:47pm
71 Sting
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Harrodsburg, KY - USA

Vette(s):
1971 Red


Joined: 5/21/2020
Posts: 1

Hello all -

 

I have a 71 that I started running last summer for the first time in over a year of sitting (pretty much). While driving it last summer I noticed it started to stutter (like it was losing fuel or spark). It eventually got bad to where it left me stranded while trying to limp it home.

When it got home I found that it would start idle rough for a moment then die. If I supplied it with fuel externally (I used carb cleaner as I was also checking for vacuum leaks) that it would pick up RPM and run happy for a moment. I deduced it was a fuel issue so I rebuilt the carb, ran the vehicle in the driveway using an external fuel tank and it ran great. I then went and connected it to the fuel tank (replaced all fuel filters) and it had the same issue. I looked into the tank and could see rust, goo, and what appeared to be a liner that had turned into a film and chinks all through the tank. I parked the vehicle as I was busy with other things so I could handle it this summer/fall and start doing a restoration (with an engine upgrade).

As luck would have it my other vehicle was stolen causing me to get the 'vette running before my budget was full enough for the upgrades  I had planned. I went out yesterday and replaced the fuel tank (better job if you have two people I found the hard way) rebuilt the carb again and thought I would be on my merry way. Unfortunately now that I have fuel in abundance I have no spark.

I decided to replace the plugs, wires, points, condensers (both dist and ign), and coil (about everything I could think that would be affecting my spark). I have to admit that points were a thing of the past before my dad even met my mom and all prior vehicle experience has been on HEI systems. That being said the ol' Google's got me the info needed for setting the gap. All installed - still no spark.

 

I measured across the coil and I have 4-6 volts. I have two wires and the condenser on the + and then the wire running to the points from the -. If I unhook all of this from the coil I get 12 volts from the wires to the + to the alt ground. I'm going to go pull 12 v from the battery to the + of the coil and see if it will start. I also was looking through these forums and found one with a 76 that was doing something similar (only he had HEI) and the issue was the tach cable. I have a mechanical tach, but I am going to figure out which wire is the actual 12 v and the one that isn't I am going to leave of and try again.

Other than that I am out of ideas, and could use assistance from you all.

 

Thanks in advance.

 

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Re: 71 no sparky spark (2/2)
 5/21/20 9:21pm
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: 19710

Welcome to C3VR !

You should expect to see 6-8 volts on the coil + with the key on, engine off. The coil gets a full 12v(or battery voltage) ONLY while cranking the engine to start. This full battery voltage comes from the "R" wire(outside small terminal) at the starter solenoid. Once the key is released from the "Start" position, the voltage is reduced thru a resistor wire from the ignition switch. Th voltage is reduced to keep from melting the points while the engine is running, but it requires full battery voltage to get it started. I would suggest you jumper 12v to the "+" terminal on the coil temporarily to see if the engine will then start. If it does start, then remove the 12v jumper to protect the points. At that point(no pun intended), you would need to see why you are not getting voltage up from the starter solenoid to the coil while cranking. Might just be a loose/corroded wire, or similar easy fix.

hth



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