Question for the Electrical Gurus; Distributer not getting juice during cranking.

[WorkinLonghorn]

'69 GMC has been running fine, then I hit some deep water (I forgot that I don't have a Passenger side inner fender). The next time I went to use it, it stalled out in traffic and wouldn't CRANK. So I pushed it. in the rain, 1/2 block while steering it away from the parked cars, finally finding a spot (hey, I'm only 70).
So anyway after sorting out the wires attached to the post near the battery (one was bare from vibration against the body), it will crank but not start. I check the lead to the HEI style distributor and I see 12+ Volts. So I bought a distributor for $50 on Amazon. Still nothing while cranking. So I run a lead from the battery to the distributor and it fires right up, just before I would have gotten a massive parking ticket. Of course, it won't turn off, even with the battery ground disconnected but at least I got it home.
I take the ignition switch off and I see that "Ign." has 12+V until the start position is attempted, then nothing. Ah! Bad switch! Cough up $30+ at Auto Zone and that switch does the exact same think; Ign.voltage cuts out during cranking.
I did wiggle the wires under there initially and my ancient brain remembers that there was some sort of jury rig in the wiring. I notice that the Brown wire is off with fresh 1/4" copper showing. I crimp a new female spade connector on there and plug it into Aux.
My question is this; If both of these switches are good, then the only "hot" terminal on the back of the switch during cranking is the "Sol" to the starter solenoid . How the heck does the ignition circuit get it's electricity during cranking.
There is one wire going from "Ign" on the fuse block directly to the distributor (not a resistor wire, I still had a brain when I did the conversion to HEI 20 years ago). The purple Solenoid wire disappears into a harness into the fuse block I think. What am I missing here? The only way I can explain it is if both switches are bad. MUCH thanks, -BA

[RustyPile]

I don't see how driving through high water or pushing a "dead" truck in the rain will cause wires to switch places in a plug, but I suspect the wires that plug into the ignition switch plug are pinned wrong. When the ignition switch is in the start position, the acc wire/circuit will not have voltage on it.. The pink wire at the plug is the ignition wire, not the brown wire. I think that possibly the pink wire and the ACC wire are switched.. Comparing what you have to the wiring diagram will tell you what wires do what, and where they should terminate in the plugs.

I offer this advice to anyone trying to solve an electrical problem.. Go to the ELECTRICAL forum on this site and down load the wiring diagrams for the vehicle year being worked on. BTW, this is a good time to correct that "jury rig" in your wiring.

[kwmech]

I've always replaced the resistor wire at the engine compartment bulkhead connector and that's it. If no juice while cranking with the OE connection it would be the ign switch.

[Richard]

Believe it is normal for IGN to lose power while in start position. Stock wiring IIRC there should be an additional wire running to starter solenoid to provide a full 12 volts at distributor during crank/start. Think the resistor wire gets power from the IGN circuit.

[MikeB]

Originally Posted by WorkinLonghorn

How the heck does the ignition circuit get it's electricity during cranking.

The switch is or should be "mutually bussed". That means the IGN terminal is hot when the key is in the "start" position. My 69 has had two IGN switches over the years, and both of them worked like that. If you have an ohmmeter, you can check that on the switch you removed.

Just occurred to me that on earlier cars and trucks, like the 1950s, that was not the case, so a later model mutually-bussed switch was required for HEI installations.

I have seen some 60s cars (like a 64 GTO) use a resistance wire for the connection from IGN switch to distributor, instead of a ballast resistor. Be sure there isn't any resistance wire or a ballast resistor between the ignition switch IGN terminal and HEI input.

I can't envision where your bare wire touched the body, but you could have potentially blown a fusible link. If the deep water incident didn't cause the problem, it would be a coincidence.

Also, the jury rigging you found may have something to do with the problem.

[Bigdav160]

While cranking the ignition is fed through the "bypass". On a GM it's a yellow wire, IIRC. Once the key is released the ignition gets it's power through the resistance wire.

When installing an HEI full battery power is required so many just find a place in the fuse box that is hot when the key is on.

[RichardJ]

>> How the heck does the ignition circuit get it's electricity during cranking.<<

I've removed most of the unnecessary wires from this drawing. I'm showing four wires on the Ign sw, although only three are needed to start the engine.

Red 12 volt wire:
Follow the red wire from the battery junction block, past the alternator to the bulkhead connector. Inside of the bulkhead connector the red wire feeds the part of the fuse panel that is always Hot and feeds the Ign sw with 12 volts.

Pink 12 volt wire:
This wire is hot (12volts) when the key is in the Run position and the Start position. This wire feeds the inside of the bulkhead connector and plugs into the ballast wire that is in the outside of the bulkhead connector. This pink wire also connects to part of the fuse panel that is Hot in Run and Start positions.

Purple 12 volt wire:
This wire is Hot in the Start position only and connects to the "S" terminal on the starter solenoid.

Brown wire.
This is a resistance wire that is part of the alternator Exciter circuit. This wire is used for the original Ex-voltage regulator and connects to terminal #4 on the regulator. On a In-regulated SI alternator, this wire connects to alternator terminal #1. This resistance wire is the same if the dash has a idiot light or a ammeter. This wire is not part of the Run or Start circuit.

On a HEI conversion there should be no wire connected to the "I" terminal on the solenoid. On a HEI conversion where the whole world insists that you must remove the ballast resistor or the sky will surly fall, there is no reason not to connect the HEI to the bulkhead connector where you just removed the ballast resistor.

[kwmech]

What the yellow wire does from the starter is give a full 12v to the coil while cranking the engine for a quicker start. Voltage is still at the resistor wire while cranking...not full voltage though.

[RichardJ]

It depends on what you consider full voltage. While the starter motor is cranking, you are hoping your 12.5 V battery charge will be providing 10.0 V. That's 10.0 V through that yellow wire and probably 8.5 V through the ballast resistor. That's not bad when you consider the same points distributor was being supplied 5.0V while cranking with the 6 Volt systems used in the 50's.

Same induction ignition system used in the 6V and 12V systems. Believe it or not 6Volt batteries actually cranked the engine and still supplied enough voltage to the distributor to start the engine. Imagine that. 5.0 volts to the coil and the plugs still fired to start the engine.

Induction coils, including ignition coils, AC clutch coils and solenoid coils, all generate a large magnetic field. All generate a high voltage when the voltage is removed and the magnetic field collapses.
AC clutch coils use a diode to protect any electronics in the AC controller.
An ignition coil relies on that magnetic field collapsing in order to generate the secondary coil voltage.
The magnetic field collapsing in the solenoid goes unnoticed in a points ignition, but with an HEI, that 300-400V spike can fry the module.
That yellow or any other wire should always be removed from the "I" terminal on the solenoid with a HEI.

[WorkinLonghorn]

[QUOTE=RichardJ;9184594]>> How the heck does the ignition circuit get it's electricity during cranking.<<

"I've removed most of the unnecessary wires from this drawing. I'm showing four wires on the Ign sw, although only three are needed to start the engine.



Pink 12 volt wire:
This wire is hot (12volts) when the key is in the Run position and the Start position. This wire feeds the inside of the bulkhead connector and plugs into the ballast wire that is in the outside of the bulkhead connector. This pink wire also connects to part of the fuse panel that is Hot in Run and Start positions."

This is the part of the puzzle that I don't get; On the 2 switches that I have, the Pink wire (attaches to the "Ign." post and that post is only hot in "Run" position NOT during "Start". The ONLY hot pin on the back of the switch during "Start" is the "Sol" (purple wire). So there must be a connection from this Purple wire to the Ign. circuit but I don't remember how this occurred after the HEI conversion. Anyway, wouldn't the solenoid stay activated with current coming from the ignition circuit during "Run"? Thanks.

[RichardJ]

>>Anyway, wouldn't the solenoid stay activated with current coming from the ignition circuit during "Run"?<<

Is you purple wire hot in the Run position?

Is your new switch exactly the same as the old switch with the acc position. Post #2 from rusty is probably correct.

read through this thread about the '67 and later Ign sw.

http://67-72chevytrucks.com/vboard/s...d.php?t=735184

[PbFut]

Couple things going on here.
1 HEI system often fail (at the worst time) if you don't provide a full 12v while running. Long term exposure to low voltage burn up the trigger curcuit. That is why it is recomended the resister wire be abandond.
2 There are 3 auxiliary pins on the fuse block.
Full time hot even with key in off position.
Hot in run and start poition.
Hot only in run poition.
2 common aftermarket upgrades are often not connected correctly. HEI needs a new wire direct to the run start pin. This avoids the resister wire and need for the jumper at the solenoid. Be sure it is not connected to full time jot pin or you will run down the battery.
Elec fans need to be connected to the run only pin. Think radio circuit. Doing so drops power to various devices not absolutely needed during cranking. Aftermarket fan draw a lot of juice so this trick help on hot days when cracking is already stressed from hot tight engine and heat soked starter.
To the OP, I would simply run a new wire direct to the run start pin with a inline fuse close to the fuse block pin. This eliminates any issues with damaged wires and simplifies the circuit. I beleive the resister wire was used to protect the points from burning.

[MikeB]

Originally Posted by RichardJ

IBelieve it or not 6Volt batteries actually cranked the engine and still supplied enough voltage to the distributor to start the engine. Imagine that. 5.0 volts to the coil and the plugs still fired to start the engine.

Depends on the engine and ignition components, I guess. The 64 GTO I mentioned had an OE distributor with HEI internals (Dave's Small Body HEI), but the installer did not know about the under-dash resistance wire between ignition switch and coil. That resulted in around 8-9 volts reaching the coil.

The engine was hard to start when cold, and very hard to start when warmed up. Also the engine did not have the performance you'd expect out of a Tri-Power GTO. Bypassing the resistance wire put full battery voltage on the coil, which solved the start and performance problems. So while the engine may start with 8 volts or less, that doesn't mean it will run good. It's kind of like using a flashlight with old batteries. You will get some light, but not the full potential of the flashlight.

[WorkinLonghorn]

Originally Posted by PbFut

Couple things going on here.
1 HEI system often fail (at the worst time) if you don't provide a full 12v while running. Long term exposure to low voltage burn up the trigger curcuit. That is why it is recomended the resister wire be abandond.
2 There are 3 auxiliary pins on the fuse block.
Full time hot even with key in off position.
Hot in run and start poition.
Hot only in run poition.
2 common aftermarket upgrades are often not connected correctly. HEI needs a new wire direct to the run start pin. This avoids the resister wire and need for the jumper at the solenoid. Be sure it is not connected to full time jot pin or you will run down the battery.
Elec fans need to be connected to the run only pin. Think radio circuit. Doing so drops power to various devices not absolutely needed during cranking. Aftermarket fan draw a lot of juice so this trick help on hot days when cracking is already stressed from hot tight engine and heat soked starter.
To the OP, I would simply run a new wire direct to the run start pin with a inline fuse close to the fuse block pin. This eliminates any issues with damaged wires and simplifies the circuit. I beleive the resister wire was used to protect the points from burning.

Wish I knew where that "hot in run and start position" pin was. I guess I'll have to start checking/ The thing is, it always worked just fine plugged into the "Ign" pin on fuse block. Now it doesn't get current during "start". Thx. BA

[WorkinLonghorn]

Originally Posted by Richard

Believe it is normal for IGN to lose power while in start position. Stock wiring IIRC there should be an additional wire running to starter solenoid to provide a full 12 volts at distributor during crank/start. Think the resistor wire gets power from the IGN circuit.

Right. I guess it doesn't matter what was happening before, I will just remove the starter to add a wire to that solenoid terminal and run it to the Distrib Ign.