Ignition Issue - Switch?

[rwantin]

Hello, did some searching first, found some things of interest, but wanted to tap into the collective here.

Like many of us, I have been cooped up a while, and decided it might save my soul if I went for a little spin. Nice day and for a change, not too hot. Car started right up, and headed out. Glorious.

Got about three blocks away and just died completely. It was an abrupt shut off, so immediately thinking it was ignition related. It cranked fine, no fire, not even a hint of it. Thankfully, some helpful neighbors came along and helped me push it back. Fun.

I did the basics yesterday back at the garage. Battery fine, connections fine, and again, will crank all day. Swapped out the coil wire, had a look at the cap, wires, etc. It's a Pertronix ignition and Flamethrower coil. Two main things determined yesterday. 1). No spark and 2). no power at the coil with the ignition on. I think that may help narrow things a little, anyway.

I have heard of Pertronix module failures but would that cause no power to the coil? The car is a Mark IV, the ignition switch has the nice key with black plastic logo (well, it was nicer than my MK II). I obviously have a multimeter, what is the best way to go about testing? I am lacking any sort of wiring diagram/schematic.

Other things of note - I have a mechanical fuel pump. And for whatever it is worth, the tach has never worked in this car.

Going back out there soon to see what I can find. Any thoughts/guidance/your own personal experience more than welcome. Beyond more than welcome, even.

[Avalanche325]

The first thing I would check, especially since you suspect a bad ignition switch, is the voltage at the primary of the coil. You should get 12vdc on the + post to ground with the switch on. If not, do the jiggle test and see if you get the voltage intermittently.

If you have that, the next thing is to test the coil. Ignition off! Disconnect the + wire and check the primary resistance (+ and -) posts. It should be somewhere in the .3 - 2 ohms range. You would be best to find the actual specs from the manufacturer. IIRC, a Pertronix coil is at the low end of that. Then check the secondary resistance. From the coil wire (the big one that goes to the distributor) to the (-) post. That should be high, something like 6k - 15k ohms.

If all that is good. It is likely the module.

[edwardb]

Assuming a Ron Francis wiring harness? While I suspect others are the same, I can only positively say for the Ron Francis harness that it's somewhat unlikely that a defective ignition switch would isolate to one circuit, e.g. power to the coil, if everything else is working. Again, at least for the Ron Francis harness, battery power comes into the switch, and routes +12V battery voltage to the headlight switch and the battery portion of the fuse panel. With the key on, that same +12V battery is added to the rest of the panel. So if everything else is working, wouldn't expect the ignition switch to be the culprit.

I don't have any experience with the Pertronix parts, so can't offer any suggestions there including the tach connection.

[rwantin]

Thanks a TON gentlemen. I opened it up yesterday as I wanted to try and track the tach issue anyway. The switch seems pretty heavy duty, not seeing any evidence of singed wiring or the like (disregard the blue tape - brain fart when I could have just simply pulled the insulation back over). Does this look like the RF harness.

I’ll head back out and see what I can determine today.

Appreciate the time, especially from such esteemed members.

131792

[Jeff Kleiner]

The Ron Francis harness has a fuse for the coil...since you aren't showing power to the coil start with the easy stuff...check that fuse. It's 15 amps labeled in the box as "EFI/COIL"

Jeff

[rwantin]

Also much appreciated. Will do!