1957 engine randomly quitting

[dn010]

So this is a new one. 1957 Sedan DeVille randomly dies while idling. Can't be fuel related because it doesn't sputter out, it just dies like you turn the key off and fires right back up when I try restarting it. I tried looking at coil connections and making sure everything is clean and tight but it still happens randomly. It happens regardless of engine temp and it hasn't happened while underway so far (luck?). Anything else I should check or anything anyone can think of that may be failing that I am overlooking?

[Cadman-iac]

So this is a new one. 1957 Sedan DeVille randomly dies while idling. Can't be fuel related because it doesn't sputter out, it just dies like you turn the key off and fires right back up when I try restarting it. I tried looking at coil connections and making sure everything is clean and tight but it still happens randomly. It happens regardless of engine temp and it hasn't happened while underway so far (luck?). Anything else I should check or anything anyone can think of that may be failing that I am overlooking?

  Dan,
  I have experienced something similar to this when my ignition switch was worm internally. Just the slightest movement of the key, (rotation), would allow the contact to break and kill the engine.

 My dad and I have also had problems identical to what you are describing. His was on a 64 Impala, and mine was on a 66 Chevrolet truck.
 What the problem was, was the main harness connection at the firewall would work loose over time and would kill everything, engine, headlights, signals. The connector is only pushed together, there wasn't any retainer or bolt to prevent it from being pulled off like newer cars have.
 I'm not familiar with the 57 Cadillac, but my 56 does not have any connector between the inside and the engine/ front end harnesses, it's all one harness in 56.
  The only other thing that I have had that killed the engine was an overheating coil, due to an aftermarket tachometer on my 56 Chevrolet. But it took about 30 minutes before it would restart after the coil cooled down.
  Good luck with finding the problem.

 Rick

[Lexi]

Well said Cadman-iac. My thoughts exactly. The ignition switch and coil came to mind. I thought the coil would first have to heat up for a while before cutting out issues arise. Not sure how long your car is running before it dies. I think these coils are filled with oil as a coolant, so if some of it has leaked out, perhaps it could even overheat rather quickly? If it was me I would first thoroughly check the ignition switch. I thought a way back I saw a post on the dissasembly and repair of them. Attached are images of a '56 switch housing disassembled. I believe the '57 is very similar (but a different part #). Last I checked no one reproduced the '56 and I have changed mine 3 times with used original parts. The issue I had with them all was random dead key at start. No cranking-no start situation. Then it might catch when I wiggled the key as Rick suggested. I don't recall the car stalling out when idling, but I guess anything is possible. Seem to recall that the area around my key-way was also hot with one of those worn out switches, i.e. resistance. Not good. Clay/Lexi

[fishnjim]

Rules of troubleshooting say, if an intermittent problem, look for intermittent causes.   Loose, thermal, vibration induced, etc.
Look at the wiring diagram in the manual for the ignition system circuit and check one by one.  I concur, doesn't look like a fuel issue.
I suspect the wire from the switch to the coil is "bad", if not the switch being worn as noted above.  I don't know what the expected cycle life is for those but, one can assume, it's seen it's better days*.   I found a lot of wire damage concealed under the harness tape on the'58.  These were wired to an old standard, that allowed multi GA wires to be branched and run on large fuses.   When the ohms go up the wire gets hotter and then resistance goes up, (vicious cycle) so won't meet voltage.  Plus eventually becomes a fire hazard.   I had one wire fire on the horn circuit.  Same thing can go wrong inside the coil but they usually burn out and not intermittent.   The connecting stud can loosen from overtightening and not stay tight.  Corrosion build up under the mounting strap, etc.
I re-wired the whole engine compartment when the engine was out for rebuild.  With a DVM and some wire/long leads one can check the Ohms from the switch to the coil, and see if higher than normal, indicating corrosion.  Shouldn't be much more than a ~10' length of 16 GA or whatever is specified. 
It might just be a loose connection, but suspect the worse in anything this old.
The ground straps at the rear of the engine are another overlooked issue.  If that ground(s) isn't good the engine can't fire.  Once it stops, you have to engage the starter again.  The new engines can shut off and start themselves without starter but that tech is 66 years forward from your cars.
Experience has shown, I always like to bite the bullet, start fresh and put new parts and wire in so I know it's good, rather than chase "weird"problems.
* - a temporary by-pass with an off the shelf universal 3 way IGN switch can confirm if the switch or not.

[Lexi]

Yes, was going to mention to run a switch by-pass to test. Clay/Lexi

[Chopper1942]

Just run a jumper with a ballast resister from the battery to the coil B+ terminal.  Start the engine. If it dies, you have eliminated all the wiring and switches up to the coil.  The issue now would be the coii or the condenser. If it does't die, then start looking at all the connections and components for the ign system between the coil and the battery.
You say that this only happens when it is idling and OK while driving. This leads me to believe that the issue is a fuel delivery problem.  The fuel pump, at idle, may not keep the carb bowl full.  I would check the fuel pressure at idle. Rule of thumb is 5-7 lbs., volume pt in 30 seconds.  Then connect a vacuum guage to the fuel pump inlet and check the vacuum: 15-18 inHg. If it doesn't meet these specs, it needs a fuel pump.  Also,the return spring for the pump lever may be broken and the lever is not returning against the eccentric.

[Dave Shepherd]

Excellent advice

[walt chomosh #23510]

Dan,
  I had a worn secondary throttle shaft that caused my motor to intermittently die at idle. Daytona replaced it and did it quick and cheap ....walt...tulsa,ok

[dn010]

Gentlemen, thank you for all your advice. I will have time this weekend to diagnose this further.

When I say it only dies at idle, it is the only time I've ever experienced it; I am unsure, with the limited driving I do in this car, if it would die at speed, it just hasn't done it to me yet. I am 99% positive it is not fuel related. When it dies, it starts right up at first crank. My mechanical fuel pump is gone and I'm using an electric pump, my carburetor is an aftermarket Edelbrock and even though it has maybe 400-500 miles on it total, I went through the carburetor last October anyway to see what sort of damage the wonderful 2022 fuel had done to it.

To begin, I will try your suggestions of running jumper & bypass wires to see what happens, I'll report back with the results.

Thank you again.

[dn010]

Nearly a year and a half later and I can finally close this case. A few days ago, I've be dealing with the circuit breaker  connected to the cigar lighter circuit constantly tripping. During this time, the engine died while I was trying to back it up. The next day, the car didn't want to start - it always starts after cranking a few seconds. So after tracing wires and unplugging nearly everything within the lighter circuit in an attempt to try to figure out what was going on, I finally found the insulation on the +12v wire going to the rear cigar lighter that is on the back of the front bench seat was rubbed bare and was shorting out on the ash tray support metal. Taped it up and my breaker is finally quiet, and my engine has not died randomly since. The cigar lighter circuit has a wire that goes to the ignition switch so I'm assuming when it was shorting out and getting hot enough, it would cause the engine to quit.