No Spark

Johnnybgood

Member
1975 V8 auto. I can't get a spark at all. I have fuel. I've changed the cap, leads and plugs. I've tried new points and condenser, and both my spare powerspark units. The engine spins well on the starter. Strange things, I have 12 volts at the coil but when the engine is cranking the volts drop to about 4.5 and no spark at all. I've tried both ballasted and unballasted could with no results. Any ideas please? Getting very fed up with this it's been like this for weeks. I've had it for over 4 years and it's been OK til recently. Thanks.
 
Points were opening OK but I've put the old Powerspark back on. I have 12.3 volts at the battery. I think there must be a dodgy connection somewhere if the voltage at the coil drops when it's cranking.
 
12.3 Volts at battery is only about 50 to 60% charged . May be worth putting it on charge before dong anything drastic
 
Check the wire from the sissy to the coil via the tachometer. It also has a ballast resistor hidden in the harness that can fail and stop power reaching the coil.
 
Thanks. I'll try both. Charge the battery and think about the resistor. Good to get second opinions as on your own you can just go round in circles.......Thanks
 
a 75 model should have the tacho in parallel ,not in series. the voltage drop when cranking would seem to be the issue. my car is a 74, D suffix engine, has a non-ballasted coil (3 ohm), 12V at the coil, works fine. Check the coil resistance - 3ohm is no ballast, < 2 ohms should have a ballast. Disconnect the coil input lead and check its volts.
 
Back
Top