Any help is appreciated...

[RCSB73]

Daily driver, 73 stock original 350..

Recently, I started getting a random loss of ignition while driving. My first though was module going out... It would randomly die, backfire, but start back up effortlessly... So I stopped in a parts store and put a new module in (yes, heat sink applied). Two days later it did it again, replaced entire distributor, it was on the list anyway. Next day same thing... Checked grounds, cleaned all connections positive and negative, getting full voltage to coil feed... I think it is in the steering column, possibly actuator rod or harness connection. I have a pretty much pristine wiring harness, no dry cracked insulation, no splices, all factory connections.
Is there anyone who has had the steering column apart past the ignition lock? Or know what I should be looking for besides between the keyed switch and coil? Had the switch out, it is in great condition, the geared cam it engages is funtional and not missing any teeth or loosely fitted.... I can't replicate the problem when parked and testing... It's completely random... Might be doing 70mph, might be adjusting the carb, might be pulling into a parking spot... Doesn't always backfire, sometimes it resumes running by itself, sometimes I have to go to neutral and start it back up, thinking of renaming it to Lazy Christine...

 

[HotRodPC]

Since I don't actually hear it, you're 100% positive it's ignition related and not fuel? Possibly a clogging fuel filter?

I mean usually you'd get a least a spit and sputter for fuel related in a carbed vehicle or does it just flat shut off? The fact it restarts makes me think fuel.

 

[RCSB73]

Flat loses spark momentarily... New carb, new filter though, been chasing other issues with bog on acceleration... Narrowed that down by seeing the marks where previous owner "adjusted" the pedal rod to get more throttle, seems like it was pulling the metering rods too far up, new trans filter and kickdown cable, bog is far less now, just playing with secondary opening rate till that gets dialed in... Biggest problem is that it has sat for 20yrs in a garage, now it gets dailied, so gremlins are bound to keep popping up.
Cruise afr is approx 14.3, hard accel is approx 11.9, idle is approx 14.0..according to cheap innovate afr setup. Would check the fuel sock on the pickup but haven't seen any lean out at wide open....
Timing is 12 initial, 30 total, vacuum advance connected is 27 at idle, 40 at 3000...
50,000v coil, new plugs and wires...

Edit: vacuum at idle is 21hg, if that matters

 

[Danderson]

I had a very similar issue with my 1977 K10. Sounds like you have an intermittent loose connection somewhere in the ignition circuit. I was able to find my problem by starting at the distributor and wiggling the +12 volt connections and wires at each juncture in the circuit with the truck running. When I wiggled the problem connection the truck died. I was finally able to narrow down my issue to a dirty connection at the firewall junction block. I split the connector and sprayed everything down with contact cleaner and haven't had a problem since.

Another likely culprit where I have seen similar symptoms is the ignition switch. I know you said you had it out and it looked good, but they are spring loaded and the internal electrical connection sliders are prone to wear and can cause intermittent electrical issues like you describe.

 

[Vbb199]

Bad ground?

 

[RCSB73]

Bad ground?

But where do I look, every ground I can find I have removed, wire brushed, (rifle bore brush on drill for internal threads, etc.) And reconnected... Tomorrow I will run a temporary toggled hotwire to coil and drive for next week... Maybe that will tell me if it is a damaged wire or bad connection assuming if its ground related, the problem will continue, and if it's positive related the problem should stop...right?

Edit: no other electrical issues when it happens, no flickering lights or anything other than loss of spark...

 

[Matt69olds]

My first thought was broken wires on the pickup coil. Since you said you swapped distributors, thats ruled out. Unless you installed a distributor with the same problem?

Check the wiring at the bulkhead connector by the brake booster. Maybe some mice have made a feast of your wiring harness?

 

[RCSB73]

My first thought was broken wires on the pickup coil. Since you said you swapped distributors, thats ruled out. Unless you installed a distributor with the same problem?

Check the wiring at the bulkhead connector by the brake booster. Maybe some mice have made a feast of your wiring harness?

I've felt and looked and wiggled and tugged, but unless a wire is damaged inside the factory loom, I can't find Any damaged or loose wires or been able to cause the issue on demand. That's what has me leaning toward bad connection somewhere in the column, has to be somewhere that I can't jiggle or clean....I have never seen what goes on inside the column as the cam connecting to the ignition lock turns so I can't mentally troubleshoot that area of the process. I'm a locksmith, so it drives me nuts when a mechanical item outsmarts me, my gut reaction is to remove and completely dissemble the column even if that just rules it out... Coming here is an attempt at not over-reacting and completely disassembling the interior before giving someone on the forum the chance to point out something simple... I really do appreciate the responses! I will take a closer look at the bulk head connections before I run the temp hot wire.

 

[HotRodPC]

Do you buy any chance have an electric tach hooked to the distributor cap? If that wire going to the tach grounds out, it'll kill your ignition. I've seen that happen where a guy didn't use a grommet to run that wire through the firewall and he was grounding out the coil and had an intermittent problem like you're having.

 

[RCSB73]

Do you buy any chance have an electric tach hooked to the distributor cap? If that wire going to the tach grounds out, it'll kill your ignition. I've seen that happen where a guy didn't use a grommet to run that wire through the firewall and he was grounding out the coil and had an intermittent problem like you're having.

Not yet.. probably run a tach at some point but just hook up the timing light with tach readout to set idle rpm etc...

 

[RCSB73]

Thanks for all the replies guys.. the more I've run through it in my head, it seems likely that the column mounted switch isn't properly engaging the "ignition" position or might be corroded.. I'll just drop the column and test it for function... Couldn't hurt to replace a 47 year old switch anyway...

 

[HotRodPC]

OK, so if you want to narrow this problem down and confirm the problem is in your wiring or ignition switch... Unplug your ignitiong wire of the dizzy cap. Run a hot wire from your positive battery to that IGN terminal on the cap. Start it up and drive it and see if you still have the same problem. IF you do, its in the coil, dizzy or ICM, if you don't, now you know for a fact it's in your wiring, ignition swith or something is ground out. That will also work to get you home if it is indeed wiring or ignition switch so you don't have to call a tow truck. Back in the day we called that hot wiring. But for process of elimination give it a try to narrow down where the problem is or isn't.

 

[75gmck25]

The key switch mounted on the upper column is just a lock cylinder, and the actual electrical switch is located down low on the column just behind the dash area. There is a small toothed “rack” that connects to the back of the lock cylinder, and then a rod that runs down to the electrical switch. It is quite common to have the pot metal rack break, and then it no longer moves the rod and electrical switch correctly.

A new ignition rack is cheap and easy to find, but a PIA to replace because it requires disassembly of the upper column after you pull the steering wheel. It should be similar to the Dorman 83211 rack and sector kit.

 

[Snoots]

Don't forget to check your Neutral Safety Switch too. It's raght neer tha ignition switch on the bottom of da column. Two fat purple wires.

 

[HotRodPC]

Don't forget to check your Neutral Safety Switch too. It's raght neer tha ignition switch on the bottom of da column. Two fat purple wires.

P N Safety Switch only affects the starter being able to engage. Wouldn't affect losing spark at all.