Hi Everyone, I apologize in advance if this question has been asked (and answered) several times before. I did a search and nothing really fits my need.

I have a small block 350 1972 Corvette. Due to an avalanche of circumstances, I stored her for the winter in less than ideal conditions. Timing issues were FINALLY over just before storage, but there's still something wrong with the electrical and I'm not sure what.
What is good: Timing, cables, coil, starter, distributor cap, battery and alternator.
What I doubt: the "power" going to the spark plugs.

What I know, when cranking a cold engine, all sounds OK, except that the "cranking RPM" is a little slow thus doesn't start... if I get a boost, she immediately starts (the "cranking RPM" speeds up").

What I know: with the engine OFF and the key in "ON" position, I have 2.8V on the coil and 4.0V on the "ceramic resistor" upstream the coil (unsure of it's technical name).

My electrical schematics don't really show it, don't know how many ohms it should be (when cold) and I don't know if the voltage measured is "normal"

edit update:
I also know that I have *only* 1.72V when cranking.
I have no clue RE condenser and points. only that my mechanic said all was good... (Bubba was here ways before)
Any ideas?

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Conclusion: bad connection on battery terminal.
Thank you everyone.
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Frank

 

The voltage in the 'on' position is irrelevant for your problem as the coil is fed a full 12V when the key is in the crank position. No C3 Corvette came from the factory with a ceramic resistor. Bubba's paid a visit. There should be a resistor wire instead.

Are the points and condenser in good condition and properly adjusted?

 

Hi Mike

I edited my post with cranking volts. They seem low. Any ideas on what I should be looking at tonight?

 

Sounds like the coil supply wiring is obviously cobbled up. It's probably a simple issue to correct, but if you can give me a couple of voltage readings we can probably clear it up quickly. With the key-on and the engine not running can you give me the:

1) Battery voltage
2) Voltage on each side of the ceramic resistor
3) Voltage on each side of the coil

My main question is trying to discern if the original ballast resistance has been damaged or bypassed.

 

As always,start at the battery.Check all of your grounds,sounds like there is a very poor one between the battery and the engine.

 

Sounds like a bad battery to me.

 

The path for electrical ground to your starter is a good place to start looking. There should be a large (2 awg) wire running from a right side frame member to a right side motor mount bolt on the engine block. You should also have a front mounting bracket for the stub-bolt on front of the starter that also bolts to the block. Wiring and wire connections must be good.

The ignition system components must be matched to what your system needs. An early C3 base ignition system uses ignition points and has s resistor wire feeding voltage to the coil (for a points system). That resistor wire is there to limit current going to the coil. You should not have a ceramic resistor in the system...unless someone removed the resistor wire and then reversed direction. If you have a ceramic resistor AND a resistor wire, I'm surprised that it runs at all. Remove the connection for that line from the coil and use an ohmmeter to measure the resistance in that line from where it comes out of the fuse block (engine side) to the place where FIRST connects to the ceramic resistor. If resistance measures more than one ohm, it is resistance wire and you should remove that ceramic resistor. You should also replace the condenser inside the distributor, if you haven't done that for a while. It lasts about 2-3 years, at best.

Make sure you have a coil that is compatible with the ignition system you have in the car.

Your starting problem is a battery or wiring issue; your running problem is in the ignition system somewhere.