tjvette

I have been helping a neighbor work out some electrical issues on his 57. He has been working on this car for years and is in the final stages. He put a new wiring harness in the car and we have already resolved some issues with connections on the ignition switch, tail lights, headlights, etc.

The starter is working and the engine turns over fine, however, we are unable to get a spark. The distributer is orginal (dual points). I took a voltage reading across the coil terminals and we are not getting any voltage with the car turned to on. When I disconnect the wires from the positive side of the coil and take another reading from the green wires that were on the positive side to the negative terminal on the coil I do get 10-11 volts. Whenever the wires are connected to the coil voltage drops to zero. This led me to believe that the coil was shorted and pulling to voltage down to zero (although the resistance of the coil measured fine). We have plenty of spare parts, so we went ahead and replaced the coil and ballast resistor but now we still get the same results.

I have a 66 vette that runs normally which I measured the voltage across the coil and I get 5-6 volts. Does anyone know what could be causing the voltage to be dropping to zero across the coil terminals on the 57?

Can someone with a 57 please measure their voltage on the coil terminals and let me know the result?


Thanks

midyear1

Have you checked to see if you're getting continuity in the pigtail wire from the points to the coil negative?

Scarlet63

Disconnect the wire on the Negative terminal of the coil.

With the swich on, and the Positive wire connected to the coil,
check your voltage.

If good, something is shorting the points.

tjvette

Hi,

Thanks for the responses.

Scarlet63,
With the positive wires (the two green wires) connected to the positive terminal on the coil and the black wire from the negative side disconnected, I have a good voltage reading between the positive terminal and ground. I will check to see if he has some spare points - we never swapped them out.

midyear1,
I checked continuity from the coil negative side to each of the connectors on both points - all checed out.- 0 ohms.

I will take a closer look at the points and let you know the results. BTW, I measured voltage across the coil while cranking since I understand that the full 12V is supplied while cranking on the second green wire. Also while cranking I get 0V so I agree something is getting shorted.

tjvette

Just to give an update - I discovered the problem. Scarlet63 was right - the points were shorted. The spade connector on the wire connected to the terminal on one set of points was turned just enough to be shorted to the base of the points. End result - the black wire was shorted to ground. Now all is working correctlty and we are getting a spark. The voltage accross the coil is at about 8V.

Thanks for the help