No Spark Mystery?

[Tom Wesenberg]

I've been working several weeks on my new Model A shed and I had so much wood and tools piled behind and on the Model A that I haven't been able to drive it for a couple months. Also during this time we've had so much rain, heat and high humidity that I probably wouldn't have been out with it anyway. This past week nice weather has finally returned and Saturday I went to the New Brighton antique car run, driving the Model A. Since it has sat for a couple months in such high humidity I was wondering if I'd have to clean the points or dry the cap or coil to get it started. It spun over fine with my old junk yard battery, but never fired, so I pulled the coil wire and held it near a head nut. The spark was very small while cranking with the starter, but very good when I opened the points with my fingers. The cap and coil were perfectly dry. I gave the points a light sanding and pulled a piece of cardboard through them, but it still had weak spark with the starter. I got the hand crank out and it started right off on the first pull. Everything was fine the rest of the day and today, but I can't explain the weak spark Saturday morning when using the starter for the first time in two months.

Every winter the car sets untouched for 5 to 7 months and fires right up first time in the spring, and I never have had to use a battery charger or maintainer. Just another one of those unsolved gremlins that may never show up again.

[Jim Mason]

I'd vote for weak battery, or poor contact through the starter. hand cranking pulls the full 80amps through the points. Like I can tell you anything about electric...fwiw,jm

[johnbuckley]

My vote would be little juice left for the essential things such as ignition circuit because of a starter motor sucking all the power maybe because of damp or minor short in it. ( may be with combined with a weaki battery). Had similar problem with a rogue starter once.

[Kurt in NJ]

I have had a sort of similar problem, when tickling the points with a screwdriver the contact is made in a different spot than when cranking --

My strange problem was opposite Toms, crank--crank---crank --no start, decide to use starter to move car out of garage into light --while starter is moving car it tries to start ---back to neutral, crank--crank no start, back to driving out on starter ---fires right up while cranking in gear moving car???, car ran fine for 100 mile trip, 1 month later same thing, no start, start while cranking car out of garage ---this time I took out moveable point screw and cleaned surface with diamond stone, cleaned point arm contact in place ---no more problem ---why it would start with the slow cranking of moving the car and not with the fast cranking of neutral I don't know--

[James Rogers]

Next time it happens,try shorting across the terminal box wire brass nuts. This takes all the wiring inside the car out of the equation. I have had this happen before and just clipped a paper clip across the hold down nuts on the terminal box and fire it right up. Once running I removed the paper clip and didn't have any more problems till it wouldn't start so, I did it again.
Puzzle?

[Tom Wesenberg]

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Originally Posted by James Rogers

Next time it happens,try shorting across the terminal box wire brass nuts. This takes all the wiring inside the car out of the equation. I have had this happen before and just clipped a paper clip across the hold down nuts on the terminal box and fire it right up. Once running I removed the paper clip and didn't have any more problems till it wouldn't start so, I did it again.
Puzzle?

That would eliminate the amp guage and two short wires running to it, but my junction box, amp guage, and two short wires are in excellent condition. Like Kurt, I also used the starter to crank the car out of the shed and into more room and light. Like Kurt said, when I opened the points with my fingers they could easily make contact in a slightly different spot on the points, but when I hand cranked I'd have thought they would be making the same exact contact as using the starter.

Guess it's time to throw away those unreliable 83 year old points and go to electronic ignition. .................................................N OT!

BTW, when you open points with your fingers you get a small shock from the higher voltage induced into the primary windings, but it isn't even enough to make one twitch.

[Milton]

Originally Posted by Tom Wesenberg

Guess it's time to throw away those unreliable 83 year old points and go to electronic ignition. .................................................N OT!

BTW, when you open points with your fingers you get a small shock from the higher voltage induced into the primary windings, but it isn't even enough to make one twitch.

Sounds like the junk yard battery is fading into the sunset! With the capacity decreasing the battery, as mentioned above, is to low to supply the starter, practically a dead short, and the coil. Path of least resistance, therefore, a weaker spark when using the starter.

I have never felt the shock you refer to. But, this is a fact, by using your fingers to open the points the spark will be better. Que paso? With fingers the points stay closed longer to allow the coils magnetic field to become fully saturated. But I bet you already knew that.

[Purdy Swoft]

With all due respect, I've got to agree with Milton. No offence but just such problems is why the auto manufacturers went to twelve volts in 55 or 56 for Ford.

[85930tudor]

I would go with the battery also. newer cars with computers wont start with a weak battery the late 80,s ones when the voltage dropped below 9 volts the computer would quit. the starter is using all the availlable voltage.

[Mike V. Florida]

Bad Battery!

[Tom Wesenberg]

I really doubt the battery is bad because it was cranking over just fine. The first thing I should have done, after checking the spark at the end of the coil wire, is to check the voltage at the coil feed primary terminal, while cranking with the starter.

[Mike V. Florida]

Originally Posted by Tom Wesenberg

I really doubt the battery is bad because it was cranking over just fine. The first thing I should have done, after checking the spark at the end of the coil wire, is to check the voltage at the coil feed primary terminal, while cranking with the starter.

What compression do you have in the engine? Would not a well worn engine with poor compression spin easy but the battery still not supply a good hot spark? That would explain the non start with the started but good start with the crank.

[Kurt in NJ]

I still think it is a dirty points type of problem, with the starter the "dwell"--points closed time is shorter than hand cranking ---perhaps when hand cranking with the ignition on the current burns through the remains of the oxide layer while you are getting a good position and grip on the crank, once it starts the arc at the points burns off the rest.

If the battery is good enough to move the car out of the garage and still crank the same it is good enough.---it has passed a load test.

[Elcastor]

Try new points just for the heck of it!

PS: Tom, what is the story behind your avatar?

[Richard Lorenz]

Tom: I have observed something similar. If the points are not working perfectly they do not provide a good spark when opened slowly. The problem might be that the points are not opening squarely. They could be rolling open which might result in a slow break instead of the sharp break that is needed. Slightly dirty points might cause the same slow break. You could test this by turning the engine by hand to where the points are ready to open, then slowly move the rotor by hand to open the points and see what sort of spark you get.

[Tom Wesenberg]

Originally Posted by Elcastor

Try new points just for the heck of it!

PS: Tom, what is the story behind your avatar?

I just like steam engines and think the American type (4 - 4 - 0) is one of the most beautiful steam engines ever built. The Pacific type (Southern Cresent Limited) at the Smithsonian is also a very beautiful steam engine, and I'd like to see it in person some day.

I agree with Kurt that the weak spark was some kind of points anomaly. I don't expect it will happen again, but if it does, then I'll check the coil voltage to be sure it's OK.

[gweilbaker]

Tom,
From all evidence, a voltage drop would have to occur at the starter cable stud between the clamp of the cable from the battery and the wire to the junction box whilst engaging the starter. To me it seems impossible due to the immediate clamp of the stud and nut junction but oxidation is a nasty word in the world of current flow and does occur everywhere.

Puzzling for sure but there is and answer to the condition you experienced, it just has not been found yet.

GW