Hi All Camaro enthusiasts / lovers !

Help needed pls ! have a 1970 396 SS. Car cranks, wouldn’t fire up. 3 to 4 volts at coil and no spark. Not sure what to do and where to start. [Had a friend come and he checked through multilmter just at the coil and says not enough volt coming. 4 to 3 Volts only. There is no spark at the coil going to the distributor.

He took this cable off and kept it close to the coil end, he connected battery positive to the coil positive, and I cranked, it didn’t give any spark.

How do we narrow it down as to what the issue is ? I don’t want to spend money on getting a new coil or dizzy only to find out they were ok.]

Note: I am unfortunately not very handy with DIYs especially with electrical stuff.

Hi there @Y2Keglide

 

Disconnect the positive side, check the voltage while it is disconnected. If that is still reading 3-4 volts that is an issue that will need address. To bench test the coil you need full time power wire and you need the strike the ground test lead. You also need a spark light or a ground wire near the top of the coil to see if you have spark.

Think of it this way the positive a negative wires on the sides charge the coil. When the ground goes away the coil fires out the top. In a original setup power comes from the hey and ground comes from the distributer. The distributers is what pulses the ground.

Is this a stock ignition?

 

Hi there @Gorn thank you very much.

I guess it is stock engine mostly but was redone in 2011. 396 (6.5L). And I assume a stock ignition (although it looks much newer, so could have been after market).

UPDATE: I checked and both positive and negative terminals of the coil are showing 12v on the volt detector. But still looks like there is no spark. (I was probably wrong previously that coil is showing low voltage).

 

Maybe you should post some pics of the ignition so we have an idea of what you have there.
Do you know if it's points fired or electronic? Is there a brand name on the dizzy or coil?
Was the car running with this ignition before and now it's failed or is this new and first time trying to start?
Are you sure there's a rotor,I've seen guys having fits trying to get a car to start only to eventually find that they forgot to put the rotor in.

 

Hi there,

Thank you. Yes the car had been running ok all along and just developed this problem last week or so. It has a rotor and I guess the electronic module within it. Could not see any ballast resistor.

The coil is Intermotor Ignition.
Dizzy is: Mallory Unilite
Par no: 4748201H
Carb EO: D-70-9

Will try to post pics.

 

Next thing I'd do is with the dist. cap off spin the motor over and check that the rotor is turning.

 

So I am guessing your whole ignition is aftermarket. Here are some videos that may help you.

I think of this more of an explanation of what you need to do for a real world coil test.

This explains how to test a coil with a ohm meter

If the coil passes these tests it MAY be good. One thing these tests do not check is load. As the compression in a cylinder goes up the voltage needed to fire the coil goes up, this can cause internal arching inside the coil. This means the coil can fire a plug sitting out in the open but not fire one that is in a cylinder. This requires some way to add a load.
https://www.harborfreight.com/in-lin...ker-63590.html ( any parts store will have spark testers.)

Now we know how to check the coil. Assuming the coil is fixed or replaced the next we need to check spark at the plug. This is what the spark test is designed for. If you have spark at the coil and not at the plug now it is leaking out someplace else. Most likely the rotor cap or a cracked distributer cap.

That assume you are getting the ground pulse from the ignition system. There are two sides of the distributer/ignition system. The primary side and the secondary side. The primary side is what fires the coil. The secondary side starts with the coil and guided the high voltage spark to the plug. So the first question to a no spark is which side is not working. You seemed to focus on the coil. There is a lot more that can go wrong even just on the primary side. I do not know much about aftermarket ignition systems so if the coil is fine and the primary side is is not telling the coil to fire

On common failure points in GM primary side was the spark model itself. Going into the testing would be moot since your setup is aftermarket. I would have to go to the manufactures website and look the their process for testing spark models and pickups.

On common failure points in GM secondary side is the rotor cap. The high voltages comes in the distributer from the coil to the cap. The rotor turn the sends the power to the different plug wires. Sometimes the rotor goes bad and the the power goes right through the rotor and into metal shaft then into the motor. If you remove the rotor and flip it over there will be a black area the highvoltage burned through the cap. With GM's HEI ignition this was 10 times more likely then a bad coil.

 

And even that is rare,I'm a fan of the HEI,pretty damn reliable and easy to service.
My old '78 GMC truck is probably the most reliable hunk of iron I've ever owned,Q-Jet carb and HEI ignition.
I think if I was the OP I'd yank that Mallory and put in an HEI.

 

Thanks to all the great help above ! Really appreciate your time and your guidance.

Unfortunately most of this is too advanced for me :-(. I will seek some professional help to get this diagnosed (and they will rip me off I am sure :-)).

I guess Classic cars is not a passion for the faint hearted and for those who do not know enough about the basics. Will probably put it up for sale once it gets started :-(

 

Don't get too discouraged ,it's probably something simple and once sorted out the car will be a gas to drive again.
Like I said earlier I'm a fan of the GM HEI dist. that will bolt right in the older motors and can be very reliable.
My old 1978 GMC (Big Blue) has one in a 454 big block,more reliable than pretty much anything I've ever owned and simple to work on.
It sits for months at a time not being driven because it gets horrible gas mileage and I have other vehicles but when I need it for whatever reason like a heavy haul or deep snow event it's eveready, I used to daily drive it back when gas was just a dollar a gallon.