Advice needed on no start for old coil/points system, test light usage.

[ArtDecoWorld]

Engine: 1962 Slant 6.
Was running a month ago. Now: cranks, no start. Won't fire with starter fluid or gas. Fuel flowing.

With key in run position, no cranking:
Test light shows bright light to one side of ballast resistor. Other side is a bit dimmer. (Makes sense as the resistor steps voltage down?). Positive terminal on the coil shows the same light intensity as the dimmer side of the ballast resistor. Negative terminal of coil shows no light. Should the negative terminal also be energized?

While cranking: Positive coil terminal shows pulsing light. Negative terminal shows nothing. I read somewhere that the pulsing at the positive terminal could be the starter fluctuating the power.

So, where to go from here? What should I see or not see at the negative coil terminal with the test light? What else to do? Thanks

 

[mk378]

The negative side of the coil should go to ground when the points are closed, and show a voltage when they are open. Either there is a short in the points/condenser/distributor circuit, or the coil is open. Disconnect the minus lead of the coil and check that there is voltage coming through the coil with the key on. If there is, check the distributor circuit for shorts to ground.

 

[Chris142]

Make sure the points are opening and closing. Wouldn't hurt to pull a piece of emery paper between them. See if you are getting 6+ v at the + on the coil. If you are it should run unless the coil or condenser is bad .

 

[Trav]

There are plenty of videos on how to do simple test on coils, condensers, and resistors but don't forget the point gap and coil HT wire.
The coil wire fires 6x what each plug wire does, when it fails nothing is firing.

 

[JeffKeryk]

Simple test is to work backwards. Hook up timing light and crank engine. Does it flash? Same check for coil wire.
Lift disty cap, crank engine. Spark? Check points gap. .016" to .020"; I forget. low 40's degree dwell...
Look for damaged points wire; it happens. Inspect cap and rotor!
Ballast will normally drop voltage from 12v to 8v.

Power to coil but no spark could be coil or condensor.

Slant 6 is one of the greatest engines ever, used in Darts, Chargers, pickups and ?

 

[atikovi]

Anybody with a vintage car needs one of these ignition bypass tools in the trunk,

 

[ArtDecoWorld]

Ok, here is some further testing I just did:
-Took distributor cap off and checked the continuity of the wire from the negative coil terminal to its connection inside the distributor. The wire checks good.
-Cranked with remote starter switch and distributor cap off. Checked continuity between the negative coil stud and engine chassis ground. If I bump the engine a little at a time, I can get either an open circuit, or a ground. Does this mean the switching is working as it should?
-I am reading no power at the negative coil stud, regardless of whether the above circuit is open or closed. Power does exist at the positive coil stud.
-Resistance between the positive and negative coil studs is about 2.2 ohms.

 

[mk378]

That doesn't make a lot of sense unless the coil had a short to ground internally. Detach all wires from the coil and test if the negative stud has continuity to the grounded case. If it does, the coil has an internal short, replace it.

You may want to just try a new coil anyway. The points and all the wiring in the car seem to be working.

 

[eljefino]

If you detach the coil negative wire, turn the key on, and tap a jumper wire from ground to the (-) terminal rapidly you should get sparks out the coil wire. This takes the distributor and points out of the equation, and, if it doesn't work, indicts the coil.

 

[Trav]

Ok, here is some further testing I just did:
-Took distributor cap off and checked the continuity of the wire from the negative coil terminal to its connection inside the distributor. The wire checks good.
-Cranked with remote starter switch and distributor cap off. Checked continuity between the negative coil stud and engine chassis ground. If I bump the engine a little at a time, I can get either an open circuit, or a ground. Does this mean the switching is working as it should?
-I am reading no power at the negative coil stud, regardless of whether the above circuit is open or closed. Power does exist at the positive coil stud.
-Resistance between the positive and negative coil studs is about 2.2 ohms.

Points open you should have 12v at the pos and neg terminal and points closed 0v at the neg, try another condenser.

 

[BigCahuna]

Years ago I had a boat with a 318 Chrysler in it. It had points and a external resister. What used to steam my clams, the boat would run perfect all day out on the water. But after the three minute ride to my slip, I couldn't get it to stay running during slow speed maneuvers. I figured out that if I jumped the resister out of the system, it would stay running. Happened in mostly warm / hot weather. I've also had the condenser crap out, which prevented the boat from starting. At the time, they were cheap, so I always carried a spare. I would get a new resister and condenser and not have to worry about it for a few years. Or, you could do the conversion to Electronic IGN, and be done with the old setup forever.,,,

 

[Propflux01]

I’d say condensor. I would go ahead and either replace the points and condensor as a set, or just replace the ignition with an electronic conversion.

 

[Number_35]

Simple test is to work backwards. Hook up timing light and crank engine. Does it flash? Same check for coil wire.
Lift disty cap, crank engine. Spark? Check points gap. .016" to .020"; I forget. low 40's degree dwell...
Look for damaged points wire; it happens. Inspect cap and rotor!
Ballast will normally drop voltage from 12v to 8v.

Power to coil but no spark could be coil or condensor.

Slant 6 is one of the greatest engines ever, used in Darts, Chargers, pickups and ?

... and the base-model Plymouth Fury I, at least in 1967. Later on, the Volare and Aspen as well. Plus there was a marine application.

It's funny, I did ignition troubleshooting on pre-electronic-ignition cars for many years, and never thought to check for spark with a timing light. I always did it the cumbersome way - pull a plug wire at the plug, stick a screwdriver blade in the plug-end of the wire, hold the shaft of the screwdriver close to ground while a helper cranks the engine, and watch for spark. (Or alternatively, pull the plug and hold the base up against a ground and watch for spark.)

The timing light makes so much sense - thanks, I'm always learning.

As far as dwell angle, the old rule-of-thumb if you didn't have the spec was to take 240 (2/3 of 360 degrees), and divide it by the number of cylinders. Thus, 60 degrees for a 4-banger, 40 degrees for a 6, and 30 degrees for an 8. (From my rusty memory banks, 30 was typical for a SBC, 37 for a Slant Six, and 52 for a Datsun B210.)

If I suspected the coil, I would take an ohmmeter to it - can't remember the typical resistance offhand, but the primary side would be low and the secondary side quite a bit higher. They would typically fail open, so a reading of infinite Ohms would be a red flag.

 

[Number_35]

Engine: 1962 Slant 6.
Was running a month ago. Now: cranks, no start. Won't fire with starter fluid or gas. Fuel flowing.

With key in run position, no cranking:
Test light shows bright light to one side of ballast resistor. Other side is a bit dimmer. (Makes sense as the resistor steps voltage down?). Positive terminal on the coil shows the same light intensity as the dimmer side of the ballast resistor. Negative terminal of coil shows no light. Should the negative terminal also be energized?

While cranking: Positive coil terminal shows pulsing light. Negative terminal shows nothing. I read somewhere that the pulsing at the positive terminal could be the starter fluctuating the power.

So, where to go from here? What should I see or not see at the negative coil terminal with the test light? What else to do? Thanks

When a Mopar ballast resistor fails, the engine will crank fine and start but quit as soon as you release the key (i. e. as soon as the key goes from START to RUN).

 

[JeffKeryk]

I had points eliminator module, MSD box and whatever in my old Corvette. Ripped all that crap out and went back to points. I even had the original coil on the shelf. Fired right up. Love my points.

 

[ArtDecoWorld]

Thanks for all the replies. Lots of good advice.
So, there is spark coming from the coil, but nothing out of the plug wires.
I changed the condenser, and did a new cap and rotor.
I can visually see the points open and closing, and as mentioned previously, resistance measured from the coil negative stud to ground goes from open to ground depending on whether the points are open or closed.

 

[Trav]

Did you try another coil wire to the cap?

 

[ArtDecoWorld]

Spark is coming out of the coil wire.

 

[zrxkawboy]

Roadside Troubleshooting

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[Number_35]

I had points eliminator module, MSD box and whatever in my old Corvette. Ripped all that crap out and went back to points. I even had the original coil on the shelf. Fired right up. Love my points.

The GM points on the V8 were the best - pop up the little window on the cap, and use an Allen key to set the dwell to 30°.