Voltage Drop across coil

[Barry_Calgary]

My 440 quit a few times while out for a run but restarted, then quit completely and would not restart. I changed the ignition module and drove it home with no issues.
Took it out again today for the first time went to the gas station and would not re-fire until I jumpered it at the starter solenoid.
Still not sure what the issue is but if I check the voltage at the coil + to chassis ground its 11.8VDC in crank and run position if I hook up the negative side of the coil which goes to the Ignition module it drops to 4.9VDC in run and 8VDC during crank but no spark?
Any recommendations on what to test next? Seems like the ignition module is drawing the voltage down but could that be ignition switch or starter solenoid related.
I'm stumped.
Thanks for your advice

 

[Barry_Calgary]

My 440 quit a few times while out for a run but restarted, then quit completely and would not restart. I changed the ignition module and drove it home with no issues.
Took it out again today for the first time went to the gas station and would not re-fire until I jumpered it at the starter solenoid.
Still not sure what the issue is but if I check the voltage at the coil + to chassis ground its 11.8VDC in crank and run position if I hook up the negative side of the coil which goes to the Ignition module it drops to 4.9VDC in run and 8VDC during crank but no spark?
Any recommendations on what to test next? Seems like the ignition module is drawing the voltage down but could that be ignition switch or starter solenoid related.
I'm stumped.
Thanks for your advice

I recall that 4.9Vdc and 8 Vdc was normal when I tested it a few years ago but now looking at some posts that seems unusually low

 

[65CopCar]

8 Volts during crank is in my opinion way too low. If it were me I would be figuring out were your voltage drops were and I would be improving them. It could be in your bulkhead connector or ignition switch. Sounds like your voltage drop is in your ignition system. It makes sense because with the coil negative off, you are not drawing any current.

What I would be doing is putting a jumper directly from the battery to the ballast resistor and see at that point what your voltages are and if it fires. If no fire, coil or ignition module would be suspect in my opinion.

 

[Barry_Calgary]

8 Volts during crank is in my opinion way too low. If it were me I would be figuring out were your voltage drops were and I would be improving them. It could be in your bulkhead connector or ignition switch. Sounds like your voltage drop is in your ignition system. It makes sense because with the coil negative off, you are not drawing any current.

What I would be doing is putting a jumper directly from the battery to the ballast resistor and see at that point what your voltages are and if it fires. If no fire, coil or ignition module would be suspect in my opinion.

I have 12 VDC at the ballast resistor, it's only when i hook up the negative side of the coil is when the voltage drops. I checked the resistance of the coil, Primary 1.4 ohms and secondary is 9.46K ohms. What are the chances my brand new Napa ignition module is the issue?

 

[twecomm]

You should see full battery volts on + side of coil when cranking as the ignition switch bypasses the ballast resistor when cranking. When ignition switch is in the run position, the ballast resistor is in the circuit in series with the coil and you should see a slightly lower voltage on the + lead of coil. You could, have an intermittent ballast resistor or coil or... some electrical connection on any of those items is having issues. 4.9 or 8 volts ain't going to cut it.
Note to self : Always carry a spare known good ignition box. It will be needed isome day..

 

[Don Frelier]

All the above are correct.
Q. Do you have a secondary ground from the back of the cylinder head to the firewall?

 

[toolmanmike]

You should see full battery volts on + side of coil when cranking as the ignition switch bypasses the ballast resistor when cranking. When ignition switch is in the run position, the ballast resistor is in the circuit in series with the coil and you should see a slightly lower voltage on the + lead of coil. You could, have an intermittent ballast resistor or coil or... some electrical connection on any of those items is having issues. 4.9 or 8 volts ain't going to cut it.
Note to self : Always carry a spare known good ignition box. It will be needed isome day..

I bought a good one and a China built "extra" from @HALIFAXHOPS. He tests every box before selling them. The old 70's "new" parts he sells are well built compared to the junk from China everyone sells today. He has the correct ballast resistors and coils for your application as well.