No spark

hb32

hb32

Well-known member
I have been having no luck in getting spark to the plugs on my C69a. Crab distributor and cap, which I have swapped out both, stock coil, 42-46 which I have also swapped out, rotor also swapped, condenser also swapped. 6 volt positive ground, switched power to the coil is good, frustrated, help
 
6 volts at the coil is good, only if the points are open. So check at the coil wire and condenser connection at the distributor. Should also be 6 volts with the points open. If not, check the distributor wire connection at the coil. If that is tight, the next step is to disconnect it at the coil and check that wire for continuity. That is, zero ohms between the coil end and distributor end of that wire. Those wires have been known to corrode internally and go open from that and flapping in the fan breeze.

If that checks good, hook the coil wire up again, put the voltmeter on the distributor side of the coil and bump the starter until the points close, as indicated by a drop in voltage at the coil from 6 volts to near zero volts. If you can not get it to drop, the points aren't making ground. Points could be fried or grossly out of adjustment; pigtail to points loose or broken, distributor housing not grounded to block.

If you do get the voltage to drop, leave the motor in that position and go back and check voltage at the ignition switch side of the coil. Should be about 4.7 volts, due to IR drop across the ballast resistor under the dash. If it drops much below 4.7 volts, the coil is drawing too current. probably due to windings shorted internally.
 
For some reason I am showing approximately 1.6 volts at switched power at the coil, initially it was 6 +. Wiring is based mostly on 32 schematic except for the addition of a starter solenoid. Is there a possibility that have an issue with the amp meter ? Thanks for the help so far.
 
hb32 said:
For some reason I am showing approximately 1.6 volts at switched power at the coil, initially it was 6 +. Wiring is based mostly on 32 schematic except for the addition of a starter solenoid. Is there a possibility that have an issue with the amp meter ? Thanks for the help so far.
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Disconnect the wire from the coil and then check the voltage at the wire. Like was said before, the points need to be "open" to check the available voltage. If they are closed then you are doing a voltage drop test. You cannot check for available voltage to the coil while the circuit is energized, current flowing (points closed). The points might have been open when your first checked the voltage and got the 6 volt reading and then they were closed when you got the 1.6V reading.

The easiest way to think of voltage is that it is the measurement of electrical "pressure". If that was instead a water pipe connected to the coil and you wanted to see how much water pressure was available to the coil you could not tap into the pipe at the coil and get total available pressure if the water was flowing though the pipe. That is because you would have a pressure loss at the end of the pipe. You would need to shut the flow off at the end of the pipe and then you would see what the the total available pressure was at the coil. Always think of what water in a pipe would be doing when diagnosing electricity. With electricity have pressure (voltage) and volume (amperage).

You called it an ammeter. I think you mean voltmeter. Make sure you have selected the appropriate "DC" and the correct voltage scale. Check the meter at the battery first.
 
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I disconnected the per from switch to coil and show approximately 1.6 volts. Hence the question regarding the in dash amp meter failure.
 
If you have a terminal type ammeter you can check the voltage on the "in" terminal and the "out" terminal to be the same.
 
hb32 said:
I disconnected the per from switch to coil and show approximately 1.6 volts. Hence the question regarding the in dash amp meter failure.
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Just run a wire from the battery directly to the ballast resister and bypass your ignition switch, dash ammeter and car's wiring. That will eliminate all that stuff as the possible cause.

I keep a bunch of different length and size wires/cables with alligator clips on each end. In matter of seconds I can clip a fire from the positive post on the battery to the ballast resistor, fuel pumps. Air condition compressors or anything else I want to bypass the cars wiring.
 
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TJ said:
How old is the wiring?
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All new wiring. Just took the ammeter out of the equation, weak spark. Still need to follow through on some of the steps as per previous posts but at this point interest and motivation are fading fast
 
Run a wire straight from the battery to the coil, and see if it starts, If so, the coil is weak and should be replaced. Many of us have our original style coils rebuilt by Skip Haney in FL.
 
4dFord/SC said:
Run a wire straight from the battery to the coil, and see if it starts, If so, the coil is weak and should be replaced. Many of us have our original style coils rebuilt by Skip Haney in FL.
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That’s what I have done, batt to coil, weak spark. Going to have a closer look at the 2 supposedly rebuilt distributors.
 
drolston said:
6 volts at the coil is good, only if the points are open. So check at the coil wire and condenser connection at the distributor. Should also be 6 volts with the points open. If not, check the distributor wire connection at the coil. If that is tight, the next step is to disconnect it at the coil and check that wire for continuity. That is, zero ohms between the coil end and distributor end of that wire. Those wires have been known to corrode internally and go open from that and flapping in the fan breeze.

If that checks good, hook the coil wire up again, put the voltmeter on the distributor side of the coil and bump the starter until the points close, as indicated by a drop in voltage at the coil from 6 volts to near zero volts. If you can not get it to drop, the points aren't making ground. Points could be fried or grossly out of adjustment; pigtail to points loose or broken, distributor housing not grounded to block.


If you do get the voltage to drop, leave the motor in that position and go back and check voltage at the ignition switch side of the coil. Should be about 4.7 volts, due to IR drop across the ballast resistor under the dash. If it drops much below 4.7 volts, the coil is drawing too current. probably due to windings shorted internally.
Click to expand...

Wire from coil to condenser checks out good.
Voltage does not drop to 0 and have checked for points grounding, which they do, gapped at .015, look fantastic, and checked for distributor ground on block, which it does. I am now using a 3rd distributor and coil. Still making no sense and has to be something common with 3 different coils, 3 different distributors, 3 different caps and 2 rotors. :confused:
 
4dFord/SC said:
Run a wire straight from the battery to the coil, and see if it starts, If so, the coil is weak and should be replaced. Many of us have our original style coils rebuilt by Skip Haney in FL.
Click to expand...

Wired directly to coil from battery. On my 3rd coil which meters out like the other 2.
 
Double checked both the coil wire and the power wire from coil to distributor capacitor, both are good. Power to coil is direct to battery. Checked rotation of distributor. Checked for ground at distributor. Still no spark and running out of ideas.
 
It appears that you and I are in the same boat.
I’m following this tread as well as the one I have going.
 
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