No spark- what am I missing?

[YY1]

OK,

1- I have verified that the coil does discharge an HV spark if the - 12v lead is grounded.

2- I have also verified that the points do spark when open, during their rotation.

What is missing is that (3-) the points grounding during rotation DO NOT trigger the coil to discharge.

If #1 and #2 are true, why is #3 not true?

What is happening differently between me manually grounding the - coil lead, and the points opening and closing?

I think my next step will be to provide a better path to ground from the dist to the neg batt terminal.
(even though the points ARE sparking)

I already tried a better path for 12v from the coil to the points.

Perhaps there is a rift in the space time continuum.....

 

[67Dart273]

I think my next step will be to provide a better path to ground from the dist to the neg batt terminal.
(even though the points ARE sparking)

....

If the engine is grounded good enough to crank, it's good enough for the distributor

BUT is the distributor clamp reasonably tight? I spose it's possible the distributor is not grounding.

But see, that's why you need to check voltage at the points...........

Jumper power to coil........

points closed.........

measure voltage at coil NEG. it should be VERY low

The higher this voltage is represents..........

(at worst) a broken distributor primary wire

resistance in the points contacts

poor ground from distributor advance plate

poor ground from distributor housing to battery

Frankly, I'd have yanked the distributor and coil out a long time ago, carried them to the bench, and wire them up there.

 

[BillGrissom]

OK,
1- I have verified that the coil does discharge an HV spark if the - 12v lead is grounded.
... the points grounding during rotation DO NOT trigger the coil to discharge.
... me manually grounding the - coil lead ...

I can't answer why it doesn't spark with the points opening and closing, but your description above is incorrect. When the points close (or you manually ground coil-), the coil magnetic field charges up. When you break that primary current flow, i.e. points open (or you disconnect the grounded lead) that causes the HV spark. The energy in the magnetic field goes into the spark. You also get a smaller spark jumping the points (not desired).

Personally, I wouldn't fool with points too long before going to an electronic ignition retro-fit kit. They have been sold since the early 1990's because they make a big improvement in reliability and stronger spark.

 

[nm9stheham]

1- I have verified that the coil does discharge an HV spark if the - 12v lead is grounded.

Can you answer if the HV sparks when the coil- lead is grounded or when the ground on the coil- is UNgrounded after you have grounded it? Should be the latter.....

2- I have also verified that the points do spark when open, during their rotation.

So does this spark occur at the moment that the point's open? If too hard to tell, then rotate the engine so the points are closed, turn the key to RUN but don't crank, and then use an insulated rod or stick to open the points and verify that the HV sparks when you OPEN the points.

We just need some clairty on what is happening.

What is happening differently between me manually grounding the - coil lead, and the points opening and closing?

I think my next step will be to provide a better path to ground from the dist to the neg batt terminal.

It is almost like the points are not pulling the right amount of current.

Did you try to make the HV spark with the point and with the condensor disconnected?

OR.....this may be the issue...... The ignition switch is set up to send 12V directly to coil + when you are cranking the engine, instead of having the 12v reduced through the ballast resistor. This makes the ignition circuit 'hotter' when you are cranking the engine and when the starter is drawing down the battery voltage which tends to weaken the spark. This circuit may be broken/not connected.

If this circuit is not working when you have the key in START and cranking the engine, then the coil may not be quite getting enough juice to fire. As a test, try a short circuit across the ballast resistor temporarily and see if the coil now fires.

 

[YY1]

The last ting I did was install a third condenser.

When I put it back together, I got no spark at the points.

I put the second condenser back in and still no spark.

I was twisting and pulling on the dist plates.

Perhaps there is an intermittent bad ground in the dist, which gets aggravated by installing the cap. (I seem to get these types of problems ALL the time, so I'm kind of used to it).

I've got an electronic dist coming from my brother.
Really didn't want to do that, but if I'm yanking and fixing, I might as will put in an electronic system for the same amount of time.

 

[YY1]

Thanks to all who have contributed.

I'll report back when and if it finally runs.

 

[67Dart273]

Perhaps there is an intermittent bad ground in the dist, .

That could be. This was common in the dual point units because the advance plate in them rotates on what amounts to a ball bearing. They always had a tiny short flexible ground wire from the advance plate to the distributor housing.

I think this is a Ferd but it illustrates the idea

 

[TrailBeast]

I still think the coil negative is constantly grounded for whatever reason.

Either the wire is in the wrong place, or the points have been miss assembled.

And I'm sticking to it.

Until a test light touched to the breaker plate lights with the points closed and ignition on, I won't believe it's anything else.