I'm having some weird ignition problems with my '66 300 i6. If I take it on a short drive and then stop for a few minutes, it won't start up again unless I let it sit for 30-40 minutes. So, for example, if I drive to the gas station around the corner and fill up, I have to hang out for 30-40 minutes to get it to start. Longer drives it seems to be less of a problem though, if I drive it anywhere for more than 20ish minutes, I can usually stop and start just fine. It's only if I try to make a quick trip somewhere close by that for sure I have to give it time before it will let me start again. Starter motor cranks just fine, it's just not igniting.

I am having some other problems that I think my distributor is causing (My distributor has a loud vibrating sound, I lose power and backfire when I drive uphill, and the idle RPMs kind of wander up and down a little). I ordered a Pertronix kit that I'm hoping will fix all of that.

Any chance the distributor is causing this problem too? Any thoughts what else it might be?

Not sure if it matters, but it also seems like my motor takes forever to warm up (Like 15-20 minutes of run time before I can put the choke back in), which seems loosely to be about the amount of time I need to drive before it will start reliably after stopping.

Lastly, all of these things only popped up once the weather started getting "colder" here. Mind you I'm in So Cal, so winter means sometimes it's 50° in the morning, I'm not dealing with sub freezing or anything like that.

 

I would suspect the carb first. Did you change the fuel pump recently?

 

I replaced the fuel pump around two years ago. Carb was rebuilt back in May. What about the carb would be causing my problem?

 

Flooding or boil over. Check your fuel pump pressure, it should be no more than 5psi.

 

15-20 minutes to warm up before pushing in the choke does sound like a long time. Are you still running the original style log manifolds for intake and exhaust that are tied together in the area of the plenum chamber? I looked back at an older video you had posted of the engine running and something also looked a little odd in the area of the oil cap and air filter. Looks like a closed system, but seemed like maybe something has been changed there but it was a little hard to make out. It looked like the oil cap hose was routed to the side of the oil bath and then the top snout was routed down the side of the engine? Anyway, pics might help a little bit of both sides of the engine.

I'd also check if you have a thermostat installed and what it is rated at. If one is not installed or the rating is very low that could keep the engine from warming up as quickly as it otherwise would. I've also come across failed thermostats - when you open it up one of the spot welds might have failed allowing the thermostat to stay partially open all of the time. That would cause some odd problems with temperature regulation.

 

In addition to the thermostat, inefficient combustion can keep the engine from warming up in a normal time.
Things like clogged exhaust (if you have one of those flapper valve thingies, it could have failed closed), poor spark, erratic spark, not enough fuel or too much fuel can cause stuff like this.
And the lack of power and backfiring when going uphill (or under other heavy loading?) can be a bad spark as well.

If you have a timing light you can test the "regularity" of the sparks by clamping the pickup on each plug wire in succession to see if you see an even pulse at all wires. Missing sparks can be due to many things, but an old tired and worn out distributor is certainly possible.
A new Ignitor unit might get rid of the problems with points, but not a problem with the distributor bushings and shaft. Or worn out advance mechanisms.
I gather you're still running points at this point? When was the last time they were changed/cleaned/adjusted? And you might even test the capacitor/condenser/thingy (if they're testable under normal conditions?) to see if it's failing. A bad condenser will give you all sorts of issues.
As will a bad radio noise suppressor (capacitor also) that is failing to ground through it's case. It can stop the spark because it's grounding itself and not letting the points do their thing.

Also, insufficient voltage at the coil can cause issues.
I would take a spare spark plug if you have one, pull a plug wire (or even the distributor wire first as an initial test) and attach the new plug, lay it near a good grounding point and look at the quality of the spark. Spark testers are great for this kind of thing, but a plug will do the job too.
If you don't have a spare then you can just remove one of the existing ones for the testing.
You ultimately want a nice be fat healthy snappy white/blue spark. A yellow/white one is acceptable in a points type ignition of course, but the more yellow and red you have vs the amount of white, is a weaker and weaker spark than you really want. And if the snap it gives is just barely audible, it's also an indicator of weakness.

Physically, you can grab the tip of the distributor shaft with the rotor and try to wiggle it sideways. It's ok for it to rotate smoothly with spring pressure returning it to zero, but it's not ok to have side-to-side movement. We're talking thousandths of an inch here, so if you have a notably wobbly shaft, it's time for a replacement. If there is too much up and down movement too (I forget the specification, but it's out there), that's also call for a replacement distributor.
If the movement of the rotor and advance mechanism is sloppy, chunky, noisy, gummy or anything not smooth and "mechanical feeling" then it's time to at least dig into the distributor to see what's up.

And last but not least, back to the whole voltage thing, what is the condition of your wiring? Got grounds? Got good wire? Got tight connections? Got clean connections? All of those matter and will deteriorate over time.
Points by their design ground through the distributor base and through the engine block. If the engine is dirty/rusty/oily inside the distributor bore, the ground path gets harder and harder to jump.

You should have 7 to 9 volts at the coil's positive side under normal conditions I think. I'm not aware of your '66 being any different from most others of sixties vintage. Points ignitions used a resistor to lower the voltage to the coil, which when you first turn the key to ON you will often see the full 12v at the coil, but it will go down shortly as the wire heats up. If your running voltage is less than 6v at the coil, maybe you're not getting sufficient power to give you a good hot spark.

Good luck. Lots of things to check sounds like. But at least it'll be worth it all when it runs good again!

Paul

 

In addition to what ONETON said, there is also supposed to be a wire coming from the I terminal on the starter solenoid to coil +. This delivers full battery voltage while cranking to ensure a hot spark while starting. My 65 was missing this wire and when I replaced it my truck definitely starts easier.