455 no start, low cranking voltage at coil

4

48469

Newbie
I have a situation where my '70 Electra, verified to have air, fuel, and spark, turns over (plenty of cranking power) but will not fire. The car is bone stock, all original, and started and ran great when I last parked it.


I'm getting spark out of the coil and at the plugs. I checked to see what voltage I'm getting at the coil when cranking. Expecting to find full battery voltage (minus some for voltage drop at the starter, so 11v give or take) at the coil when cranking, I only get 6v. This is what I'd expect in the run/on ignition position, but not what I'd expect when cranking, when power comes from the starter solenoid's R post and bypasses the coil wire's in-line resistance of 1.8 ohms (according to the wiring diagram). I measured 11v (battery voltage minus starter voltage drop) at the solenoid's R post while my wife cranked the starter, which is what I'd expect.


How can I get 11v out of the solenoid while cranking, but only 6v at the coil while cranking?


Anybody have any insight into this? Assuming this isn't normal, what's the most likely or least likely explanation for this? Am I on the right track or going down another rabbit hole?


Thanks,
Lee
 
You more than likely have a bad battery that can't hold the amperage draw while cranking.
A possible problem is bad battery connections or bad grounds. They don't just need to be tight but clean & shiny on the connections.
Next, don't just say it's new have it checked with a GOOD battery load tester.

Tom T.
 
I'd try connecting the coil directly to the battery by a temp. wire (which has to be disconnected to stop the engine!).
If the car starts now, the problem has to be located between the starter/solenoid and the coil.

Cheers,
Harry
 
Agree 100% with Harry using a 12v jumper wire from the battery. The only thing I would add is that if the car starts you should immediately disconnect the 12v jumper wire so you don't burn the points (assuming you have points and not an electronic conversion kit in the distributor.) Once the 12v jumper is disconnected the car should continue to run if you have 6 volts at the coil. My guess then would be a suspect solenoid or wire. Good luck with the problem...

Ken
 
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