1969 Engine Wiring Harness Replacement - will not fire

[Richard M.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

James,

That's what I thought too. See my post #3 above. But Rich then gave me an education on TI, so I don't think that's the problem. If I understood him correctly, when the ignition switch is in the START position, the TI module acts as a relay and sends the voltage to the coil, so the resistor wire from the ignition switch to the coil isn't needed. In my case (non-TI), Bubba replaced the resistor wire with a common piece of wire he cut from his old tractor and added an external ballast resistor from an old refrigerator that he attached to the firewall with a drywall screw.

-Floyd-

Floyd, Yes at Crank the feed voltage resistor wire is bypassed and supplies full Bat+ directly to PU coil and TI circuits. After Crank and engine running, the circuit voltage reverts back to raw IGN power. Since the alternator is now charging and potentially 13-14 volts, the resistor wire in the feed circuit takes over to reduce voltage to both the PU and the TI Module. The feed resistor wire is around 0.7 ohms. I've never measured the running voltage at the TI module or PU inputs, but probably in the 12.5v range as a guestimate.

TI is more thought of as a electronic high speed "switch", i.e. transistors, to trigger the primary Ign Coil+, and Coil- is fixed directly to ground(66-71 TI).
Note on 64-65 TI, Coil- is actually grounded via the resistor wire, and coil+ directly from TI output transistor circuit, not through a resistor. Explanation for this change in configuration? I have no clue.

Rich
PS - a few years ago I did some TI bench testing to diagnose and old Delco circuit. Some waveforms of the "switches" included. HERE
Full thread HERE if bored.

[Floyd B.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Thank you, sir. I learn something new here every day.

[Richard M.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Hi Rich,

Yes, I do have an inductive timing light, whatcha thinking?

I do have to take a pause for a bit as I don't have any time during the week and am out of town this upcoming weekend. I was concerned that perhaps I may have turned the distributor rotor when it was pulled, so I actually pulled a few spark plugs, reset the motor to TDC on compression at #1, reset the rotor to pointing at #1, reinstalled plugs and tried to fire again - no change.

Peter, I was searching the forum and came across this old post.

I know this thread is over a year old, but did you ever get this resolved?

Rich