1963/64 Cadillac Starting - Cranking System Basics

[Jason Edge]

I have had this info written up for some time and meant to post so here it is. I will link to this from our Help Page:

1963/64 Cadillac Starting - Cranking System Basics

Wiring
You have a positive cable from battery to the large bolt on the starter solenoid, a yellow wire from the (R) side of starter solenoid switch to the ignition coil, and a dark blue wire from the (S) side of solenoid to the Neutral Safety Switch, which in turn is fed by the purple(violet) wire from the ignition switch. There is a large ground strap from right frame rail to transmission bell housing bolt to engine block.  The frame is grounded directly by the negative battery cable which attached to the frame on the right side just in front of the radiator support under the battery tray.

The Neutral Safety Switch Prevents Cranking in “Drive” Gears 
The blue and purple cranking circuit is closed when the shift selector is in Park or Neutral, and open in any drive gear in order to prevent cranking the car in gear.
  
Starting - Cranking
With ignition switch turned to far right cranking position, the purple wire feeds the 12 volts to the blue wire at the neutral safety switch which feeds the starter solenoid switch. The yellow wire from solenoid switch in turn provides a full 12 volts back to the ignition coil for cranking. When you release the switch and have the switch in "run" position, the voltage to the coil is reduced to 8 1/2 to 10 1/2 volts since current is then  provided through the brown resister wire, which gets it's current at the pink ignition wire under the dash.  On the solenoid switch, the outer terminal away from engine is marked R and has the yellow wire connected. The inner wire is marked S and has the blue wire connected. The yellow wire is often dirty and hard to see the color and requires some cleaning.

Cranking Problems
One of the most important and overlooked components in the cranking circuit is the large ground strap that runs from the right frame rail over to the large bolt through transmission bell housing to engine and starter. If this is not connected and making good connection your starter will not work.   Check your ground strap and make sure it is making good connection.  If all other wiring is connected correctly, you could also have a bad ignition switch or melted and shorted ignition switch connector. Remove lower dash panel and disconnect the ignition switch connector and inspect closely with a light looking for melting and shorting. If all looks good, you can bypass the ignition switch and hot wire the car as noted below.
  
Hot Wiring
You can disconnect the large connector on the back of the ignition switch and hot wire the car by connecting the red (battery) to pink (ignition) wire and touching to Purple (starter).  I had a switch go bad on the way to a car show a few years back and made a quick 3 way jumper to hot wire the car. Here is a video showing how simple it is: https://6364cadillac.ning.com/video/hot-wired-ignition-switches
 
Bypassing the Neutral Safety Switch is Easy  
It is just a matter of unplugging the connector with the purple and dark blue wire and jumping the connector.  Be aware the car will now crank I any gear.

[Jason Edge]

Bumping this up since we have had some newer questions about ignition and cranking wiring.

[Dennis P. DiBari]

Linda,

     I concur.  This is a great review of all the wiring and the grounds straps that are paramount!  Just replaced some of mine recently.  Dennis DiBari, NY

[Linda M. Brooks]

Hi Dennis,

Yes now I have electrical issues, left VA Thurs am, drove 7 hrs and in Notwich, OH.  I stopped for gas twice and once at a rest area, car shut off and restarted without a problem.  Stoped at a BP at this exit to get directions to motel, shut car off.  On restart it sounded different (starter), but ran OK.  Motel just down the road, and I couldn't shut the car off.  Pulled in front of room, put in park and pulled the coil wire - couldn't find a ground fast enough so it went through me.  Thought it was my ignition switch but it ohms out OK when cool.  Long story, but replaced switch with aftermarket 4 terminal one and now no start.  Checked wiring at starter/solenoid, cleaned terminals and ring connectors, no breaks or shorts.  Glad my sister is with me but hate putting her through this.  Going to get her to turn key while I check for voltage at solenoid.  Wiring to NSS and to ignition connector (dark blue and violet) ohm out ok.  Getting frazzled, some snow may be coming Sun night.  Was recommended a good repair shop down the road, but had to try myself first.  Oh, I do see the large ground strap between frame and trans/engine but haven't removed and cleaned.

[Linda M. Brooks]

Well, just checked voltage @ starter.  10.8v at dark blue wire at solenoid from NSS with key in start, and 6v at yellow solenoid wire from coil.  Volts at coil + yellow wire is 12v.  I know this is bad.  Battery reads 12.6v sitting.  

[Jason Edge]

Your voltage drops at the ignition coil in the "run" position. The resistor wire (brownish) drops the voltage to about 10 or so volts to help protect the points. You would only have the full 12 volts when in the crank position with key turned all the way to right like you are cranking the car. When you release the key to run position voltage drops to the 8.5 to 10.5 to ignition coil as indicated in write-up. 

[Linda M. Brooks]

Thanks Jason, very good write up!  Yes, my sister had the key to full right/start and volts @ the R solenoid terminal/yellow wire were 6v, and 10.8v at the blue solenoid wire.  Correction re: yellow wire on coil (paired w/resistor wire) also 6v in start position.

[Jason Edge]

From the description, and given the fact you have tried replacing the ignition switch I might try replacing the solenoid switch. The ignition switch and starter solenoid switch is where several wires come together and can do weird things if they short or ground. Make sure wires to/from solenoid are tight and not touching metal as they go down/up the right rear of engine. They can burn from the exhaust manifold if not shielded or away from it.

[Linda M. Brooks]

Yes, actually disconnected those two wires, felt them from underneath the car and they were routed too close to the manifold, where it melted the plastic loom that was installed by previous folks.  I failed to see that before.  I cut away the damaged loom, and found the blue, yellow and #10 red wires were OK.  Cleaned them up, re-routed them closer to the block and above the starter, and reconnected them.  It was after that that I checked the volts at the blue (10.8) and yellow (6) wires on the solenoid with key in start.  Ign and NSS both had 12v.  

I've been reading that a bad starter can kill a solenoid, and there are very few aftermarket ones, mostly out of stock, and rebuilt ones on eBay for $325 and up.  Solenoids are more readily available.

Jacked my baby up and can get to that ground strap so will pull that off soon and clean things up.  Just checked voltage at the #4 cable from +battery to starter motor lug, and reads 12.8, like the battery reads now.

Thanks for your input Jason!  Also, I've never done a Zoom before and not sure where I'll be on that date, hopefully home.  My tablet has the camera and maybe a mike, but my HP does not.  May need instruction on that....

[Dennis P. DiBari]

Hi Linda,

     Was thinking about the long trip you were taking after we spoke.  This is terrible that you got stuck with this ignition problem on the road, no less.  I read your post and you have checked everything correctly.  The sitting battery seems fully charged at 12.6 V.  Changing the ignition switch was a good try - it's too bad that was not it.  If possible, loosen the bolts and clean that Main Ground Strap.  It is worth a try.  This is a tough diagnosis on the road.  It might be worth it to put back the original ignition switch, and try again to start it.  It could be the main ground, but this is just a guess.  I don't know how old your starter is, but could be drawing too much?  Sorry I can't be more help to you.  I hope you get it going or get it to a garage.  If you can, keep me posted and good luck - be careful.

Dennis DiBari

[Linda M. Brooks]

Thanks Dennis!  I think by the trunk stuffed with spare parts and tools I was ready for anything else to happen.  I'm not the sharpest tack in the box when it comes to electrical problems, but I'm trying!  Jason's Cranking Basics is super helpful, and good to be able to learn more about this car.  It had previous owner/mechanic messes besides the vacuum tubing, such as live 12v wires to the trunk (Amp or audio stuff?), the thermogauge wire twisted and taped to adapt a ring terminal, non-soldered splices to 3 of the voltage regulator wires, a fairly new alternator with female spades in place of the DN connector and more.  I have noticed the resistor wires have a brown cloth covering, like the coil resistor wire.  There is a black cloth covered wire where they crimped a female spade connector to, and I don't know where that goes.  It was on the RH side of the firewall area, I thought it was to the A/C compressor clutch, because that was rigged too.  I removed the compressor, would like to replace the seals one day, I still have some R12.

I will jack it up and get to that groud strap as soon as I can, maybe it is corroded and I need to eliminate that possibility.  I did put the original ignition switch back in, no change.  It doesn't look bad, nothing in the harness is melted and it checked out good with the ohmmeter.  That starter could be original, I see the old Delco logo on the solenoid.  Maybe the voltage drop is the ground strap or bad solenoid, I'm losing juice somewhere.  I did have 12v from ign switch, through NSS with key in start, but not at the solenoid.  Heck, I appreciate you listening to me and your input, really.  Thanks, I'll let you know what happens.  If the starter is bad I'm sure I can change it out here, can't be heavier than the Caprice starter.  Odd that it would not shut off and now it won't even crank - seems like two problems.  Have a good night,

Linda

[Dennis P. DiBari]

Hi Linda,

     See how the main ground strap looks.  Try to remove it, clean and sand the connection points to the frame and housing.  Look at the negative battery cable as well and the ground strap there on the front radiator frame.  If the starter is drawing too much amperage, could be a bad solenoid or armature in the starter.  Wish I was better with the electrical system as well, but what I am suggesting is what I have experience with.  You really checked everything and you were very thorough!  I am hoping it is in the starter and you get on your way to Montana.  If you can, keep me posted and again, good luck with the mechanic work. It is terrible when someone works on the car and they really mess it up.  I try to do most of my work, but sometimes it's too big a job without a lift.  Sounds like they really made a mess of some of your wiring.

Dennis DiBari

[Linda M. Brooks]

Hi Dennis!

Yes, heading back out to remove that ground strap and do just that.  I can see it's not broken, maybe a little tattered along one edge.  Since it's bolted to the aluminum bell housing there may be corrosion there.  Bad of me not to check that one, I removed the two at the rear block to firewall and cleaned and polished the copper braid a bit, also that battery ground you spoke of.  They cut off the original terminal end and added another #4 ground cable to the alternator bracket, I left it like that but cleaned it up, including the original braided one at the radiator frame.  I always clean and scrape the surfaces too.  My battery is a fairly new Interstate, and I did replace the positive cable and new #8 alternator cables, suggested by PoweMaster.  I have the alternator that was on the car in the trunk, just in case.

I really appreciate you sharing your experience and your suggestions, they are very welcome.  I try to be thorough, maybe too much sometimes.  I couldn't stand looking at the dented vacuum canister, probably dinged when they pulled the engine, so I removed it, loosened the clamp, and rotated the dent to the firewall.  I know I'm sick, an old friend says I'm a special case, ha ha.

Snow and really cold weather coming, I have to make the decision tomorrow to get help from the garage close by or get a solenoid or starter shipped here, may be able to get the solenoid locally.  OK, back outside, not so wet now.  Take care and will keep you posted,

Linda