59AB no spark at plugs

M

macbubba

Junior Member
Howdy, `42 -`48 Crab style Disto. Over night I suddenly lost the spark to the plugs?? Coil, Wires, Batt all check out. Could it be the condenser or should it start even if the condenser is bad? Thanks for any help. Another question, 6V system, there is a resistor on the coil - side, is this normal?
 
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Check the voltage across your battery. Should be a little ove 6 volts. Then with the ignition on, check the voltage at the coil. If the points are open, the voltage on both sides of the coil should read very close to battery voltage. If zero volts, start tracing back to the ignition switch. If you have battery voltage on the coil side of the resistor, you have a bad connection or broken wire to the coil. If you have battery voltage on the ignition switch side of the resistor but not on the coil side, the resistor has gone open circuit. If zero on both sides of the resistor, check for voltage to the resistor at the ignition switch. If you have battery voltage there, the wire from the ignition switch to the resistor is open. If zero there at the resistor side of ignition switch (with the ignition switch on, of course), check voltage on the battery side of the ignition switch. If you have battery voltage there, the ignition switch is bad (not uncomon). If you do not have battery voltage on the battery side of the ignition switch, the wire from the battery side of the starter solenoid to the ignition switch has gone loose or broken, or has a corroded connection.



If the points are closed, the voltage on the battery side should read about 4.5 volts, the drop being caused by IR drop across the resistor. The voltage on the distributor side should read very close to zero. If the voltage is less than 4 volts, the resistor may need to be replaced; but check the wire from the resistor to the coil for internal corrosion. If you see any green corrosion on either end of that wire, it must be replaced.



Too get between open and closed points you will need to turn the engine small amounts. That can be done with a big wrench on the crankshaft pulley nut, but it is usually easier to put the car in high gear and push the car a few inches while watching for the voltmeter on the distributor side of the coil to change from battery voltage to zero, or vice versa.



Good luck. Report your findings please.
 
Hi Again, Do I really need a resistor on the coil if I have a 6V battery on a 6V system with a 6V coil? Thanks
 
There should be a resistor on the circuit breaker panel up under the dash on the firewall, to the left. Stock type 6v coil needs that, but not a resistor on the coil itself. Maybe post pictures of the breaker & resistor panel, and of the coil. In either case, the results of the voltage tests will be interesting.
 
It should be noted that the 4.5 volts at the coil noted in post #3 is for a running engine only!
If you are taking a reading on a stopped engine, will be closer to 3.5 volts. Later with engine running, points open 20% of the time, averaged voltage will jump up to around 4.5 volt.
 
JayChicago said:
It should be noted that the 4.5 volts at the coil noted in post #3 is for a running engine only!
If you are taking a reading on a stopped engine, will be closer to 3.5 volts. Later with engine running, points open 20% of the time, averaged voltage will jump up to around 4.5 volt.
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I forgot that I knew that. Good catch.
 
Hi all, everything checked out on what Drolston & JayChicago sent me, thanks for that. A local shop thinks its the Cap or Rotor & both look perfect to me, I can hold coil wire while cranking & it has spark, not like a 12V coil, can I burn anything up if I try to jump with a 12V battery? Thanks again.
 
Jump 12v straight to the starter and bypass anything going into and under the dash, you can burn your coil up for sure!!! Your starter should handle the 12V's to get it to spin. I wouldn't sit there and grind and grind on it. You should be able to feel the starter IF you can't seem to get it going and make sure IT's not getting super hot!!!
 
macbubba said:
Hi all, everything checked out on what Drolston & JayChicago sent me, thanks for that. A local shop thinks its the Cap or Rotor & both look perfect to me, I can hold coil wire while cranking & it has spark, not like a 12V coil, can I burn anything up if I try to jump with a 12V battery? Thanks again.
Click to expand...


The starter will take it indefinitely, as long as you do not crank too long at one time. Any lights that are on may burn out. If on 12 volts very long, it may also burn out gauges and sensors.



Pull the coil wire from the distributor. Was it fully inserted? If not, it may appear dirty. When cranking, you should get a half inch blue or white spark from the end of the coil wire to ground. If that is good, hook the coil back and check at several spark plugs. If not equally good there, it is your rotor, cap or spark plug wires. Pretty easy to see if the rotor is bad, but a cap can be bad but not obvious.
 
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