If you look at the bottom plate for the points, you should see a notch in it that corresponds with a triangular hole in the distributor plate. You slightly loosen the points mounting screw, then stick a flat blade screwdriver into this notch and have some one crank the engine while you “adjust the points”.
Be sure the screwdriver has an insulated handle, just in case.
Yup, thanks, I know all about the notch and screwdriver trick. So you’re saying the dwell meter still works this way? I thought it might, but wasn’t sure. I’ll give that a try tonight. Though I think I first need to figure out why there’s no voltage crossing the points when they are closed. I do have an emery board to use.
Points open: Bright light on both coil posts and movable arm of points.
Points closed: No light on points or at negative side of coil.
If this is not the case, replace the points. You can try cleaning the points, filing them, sanding them, but this seldom works for long if at all…
On a 6 cylinder, dwell angle is less critical than a V8…Set the new points about .018-…020" and that should do it…
If you’d really like to get the motor running and perhaps driveable again: I’d replace the cap, rotor, plugs, plug wires, points, and condensor. These all standard tune up items on a car of that era. You can use a feeler guage to set the points, a dwell meter is a bit more accurate. Then see if you have spark. If yes, the car should start and it it runs smoothly after a bit you can check and set the timing if needed.
If no spark, a coil is easy to check or just swap in a known good coil and try again. Your distributor is likely a vacuum advance for quick response and may also have a centrifical advance. If the car runs but not too well you might have some issues with the old distributor after sitting so long. If you are getting power from the ignition switch to the coil, then getting “spark” shouldn’t be hard to track down any problems.
Coil and plug wires of that era cars sometimes were carbon impregnated radio resistance wires which were just junk. If you leaned on them they would break internally and then cause all kinds of problems, misfiring and backfiring commonly. It is very possible those old coil and plug wires are completely wasted internally while they might not look bad to the naked eye. That’s why I’d start off with new cap and wires etc. to reduce the possible problems you might encounter.
Thanks Caddyman. I just double checked, with points closed I still get bright light at the points, and at the neg post of the coil. So I guess that means that the points are bad according to what you wrote. I’ll try later to clean the points just to see if that does anything.
@Uncle Turbo. Thanks for the careful explanation. The vehicle is being sold as is, buyer wants the engine to rebuild, and the body will be scrapped, so it’s not really worth much effort. I was just curious if I could at least find the spark problem, not necessarily intending to solve it - sort of as academic exercise. It looks at least that the points are bad. I have a spare set and may swap those in if cleaning them doesn’t make a change. After that, I won’t spend for wires, cap, etc, it’s just not a priority, but I would if I wanted to make this thing run. I’m sure the wires are worthless now too even if I have no data to prove that. But I’m grateful for all the information I’ve gotten, thanks everyone. This will be helpful for a project I’ve been considering that might be more worthwhile.
If I get this beast to start, I’ll report back, otherwise, I’ll let the vehicle (and this thread) rest in peace. Thanks everyone for all the clear and detailed instructions, they have been very helpful.
–Roadtripper
This vintage ignition system is actually very easy to understand. Put simply, a 12VDC that runs through the points is turned on and off by the points, which are opened and closed by the cam on the distributor shaft. Eberytime the points are closed, current runs through the coil primary windings. When the circuit is opened bu the points, the field collapse induces a voltage spike in the coil core. The rotor directs the voltage spike to the appropriate spark plug, where it arcs across the gap to ground.
Thanks Mountainbike. That’s pretty much what I understood. I’ve long known about the concept of collapsing field generating high voltage spike (took an above average number of physics classes way back when). I’ve always thought the lowly distributor was a clever - if not elegant - way to create the high voltage and send it where it was needed. This much I understand, I’m clueless on modern electronic ignition with all the sensors etc.
I’d guess the ol’ girl simply needs new ignition points and condensor. She’ll probably spark right up after that.
If that doesn’t work, – well, there’s lots of things that could be full of cobwebs and not working correctly – so ask back here.
OK, I can’t give up yet…I have some intriguing observations.
I’ve reset the points to about .016 or so, and then checked to see the indications from the test light. Still getting a good bright light on the neg terminal of the coil. Still no flashing on the neg terminal when I crank the engine, but the light does get dimmer when it’s cranking. I can definitely see the points opening and closing, and I’ve cleaned them a bit with an emery board.
I connected my simple dwell meter - black to ground, red to the neg side of coil. The scale for 6 cyl is 60 on the left side, 20 on the right. The needle rests on the left, that is, near 60, or zero on the rpm scale. When I put key in ON position (before cranking) the needle pegs to the right, so showing less than 20, presumably zero since it’s definitely pegged. If I manually rotate the engine to open and then close the points, the meter doesn’t budge. Same when I crank the engine, the needle doesn’t flicker at all.
So I’m guessing the problem is in the distributor, and related to ground or lack of it. But I’m not clear enough on where there should be 12v and where zero voltage. Does it sound like I’m on the right track here?
As posted previously please check rotor and distributor cap.
The rotor and cap are not involved at this stage, I’m working on the 12 volt side of this. The 12 volt circuit is not doing what it’s supposed to do, flowing then breaking. It’s probably the points but I can’t see anything even with points out of the distributor in good light at my desk.
Starting at the battery current flows from the battery to the ignition switch, then through a resistor wire (or ballast resistor) to the POSITIVE side of the coil. Through the coil and out the NEGATIVE side, then to the points. The points have only one place to connect a wire, so this is the COIL side. When they’re closed current continues through the points to the body of the point set, to the plate the points mount to. This plate, called the breaker plate moves with the ignition advance, so it is not directly grounded. It needs a wire from the breaker plate to somewhere inside the body of the distributor. Once current gets to the distributor body it can go directly to the engine block since the distributor is directly connected to it.
If you can measure 12 volts all the time at the points themselves the wire connecting the breaker plate to the distributor body is broken. This is not too uncommon, since the plate moves every time the spark advances and retards, so it moves a lot. It’s 40 years old, so it may have flexed one time too many.
@JayWB: That makes perfect sense to me, and it’s one of several things I didn’t know about distributors. However I’m thinking it’s a different problem since I can’t get 12 volts on the stationary contact point when the two points are closed.
When they're closed current continues through the points to the body of the point set, to the plate the points mount to.
The current is just not crossing between them. I can’t see a problem, but there must be one. I’m going to pick up a new point set, to check that out, and I’ll look for that breaker wire that you mentioned. I’m SURE you’re right that the years of motion for advancing the dist has damaged that wire.
Thanks very much for this explanation.
Have you disconnected the wire between the points and condenser and checked for dwell? A shorted condenser can cause no spark.
I do think you need new points, but if you ever get 12v on the stationary side of the points, you have a problem. That side is grounded so it should always be 0VDC. If the points are closed and you get 12VDC on one side of the points, then there is no conduction through the points. When closed, all the voltage should be dropped by the ballast resister and the coil, mostly the ballast resistor.
Since you stated that the test light probe is lit but isn’t flashing while it is placed on the minus side of the coil while the engine is cranking it means that the connection to the points is open somehow, or the fixed side of the points isn’t connecting to ground somehow and that would be kind of hard to believe. Use your probe to verify power is getting to the points where the wire from the coil connects to the disty and to the points. If you have no power there then the wire is broken internally.
If you want to verify that the fixed side of the points are making a ground connection then tie the clip lead of your test light to the minus side of the coil with the ignition ON, or to power. Then touch the fixed side of the points with the probe tip and see if the light turns on. If it does then the connection to ground is ok.
that would burn up the points thats why you have the condenser to absorb the the spark from the ppoints opening an closen
Parts makers developed a “Uniset” points and condenser in one unit for the GM V8 engines. I don’t know if they were ever used in the 6 cylinder engines, but they were often troublesome on the V-8 engines…
From what you are describing, the points you are using are shot and simply not conducting when they are closed or they are not truly closing completely, jamming or friction at the pivot point holding them open enough so a good contact is not made…
Most distributors did indeed use a ground wire between the movable breaker plate and the body of the distributor… If this was the problem, BOTH the movable and fixed contacts would show 12V with the points closed…I think if you obtain a NEW point set, your problems are over…
I was lossing spark intermittently on my boat. I found the ballast resistor was loose and bouncing around in its mount and was shorting out. One side of the resistor had contacted the grounded metal mount. I just had to tighten things down and all was OK. You could have a bad ballast resistor.