Weak spark

The Voltage Drop "across" the Ballast is dependant on the current in the Primary Circuit.. The higher the voltage.. the higher the current... It is the current that is important to the Coil..

Normal System = ~ 3.2 Volts

Marginal System = < 2.0 Volts

If you have low voltage across the Ballast it means you have some unwanted resistance in the circuit...,Wire connections, ignition Switch,Bad Points, Bad Ground connection in Dist, etc.

Just hook up your meter to the Ballast and then jumper Stuff until the Voltage Jumps Up to Normal, and you have found your problem.

Hope This Helps,

Sounds like you need a good tune-up with correct specifications. Yes, I concour that your description is consistant with weak sparkies.

Modern no-lead gas needs hotter sparkie heat range Autolite AL-437 or Champion H-12..... gap 0.025

Ignition points..... .gap 0.015.....too wide a gap gonna give you weak sparkies.

And while I recommend nice soft flexable coppercore sparkie wires 'cuz old hard cracked sparkie wires gonna cause misses, not stop ya from runnin'.

BUT if you have modern anti-radio static carbon core, that carbon is gonna cut yer sparkies and cause missin' after a couple hours runnin' time. Be smart and replace with NEW COPPER CORE sparkie wires, ok?

As for voltage readings, a good OEM 6 volt frontmount (with mandantory "infamous ballast resistor") should read with points closed about 3.5 volts (2.5 min, 4.0 max) and 6 volts with points open. Any other volts gonna give ya sparkie problems..... .....respectfully, Dell

My voltage drop story is about a '79 Datsun 280ZX w/fuel injection. JUST DIED one day. I replaced ALL the sensors, tried a new "brain". Nuttin doin'!!! Figgered I'd re-terminate the battery cable ends since they looked nasty and corroded. Guess what!?!?!?!?! IT STARTED!!! The voltage drop at the corrosion was enough to keep the fuel injectors from opening!!!!! !!!!!

Nuff said..... ..... ....