Simple Wiring Question I Hope..

[Badcat]

Accel HEI Dist./Coil, one wire from ign switch. Should the switch allow continuous power in ON and START?

[Ironangel]

Run the 12ga wire from the switched spade terminal on the fuse block. Wire will remain hot during start. I'll see if I can find a pic... See the two terminals marked "IGN unfused?" Either one of them will work nicely...

[Badcat]

Thanks, that's what I thought and actually that's what I have but for some reason I'm losing juice when I go to start... switch maybe???

[Ironangel]

What year of truck do you have? Those two terminals should remain hot during start and run, unless the fuse block or the ignition switch has been molested...? You need to run a new 12ga. wire from either of those two terminals because the original ignition wire is a resister wire only allowing 8 or 9 volts to the old points distributor. The original ignition wire was brown if memory serves correct, discard that wire and run a new 12ga. wire. And yes, if someone tried to run an ignition wire from the ignition switch itself or confuse the purple solenoid wire for the ignition wire then you would only have power while the key is in the start position. Make sure you have a good ground from the battery to the engine block as well as good clean surfaces on the distributor hold down clamp. Theres always some voltage drop during start while the starter is engaged but as long as your getting a full 12 volts to the dizzy while the key is on you should be good to go...

[Badcat]

Micheal,
It's a '72 but a bit mod-ed, you can see the it here..

http://67-72chevytrucks.com/vboard/s...d.php?t=746354

Looks to me like when they added the Accel they ran a new wire (12ga) from the IGN UNFUSED to the coil, just as you suggested, and that is a good 12V in the ON position. As soon as I go to start it drops to "0".
The truck is "new to me" and I noticed the issue the day I picked it up, but the previous owner said he never had a prior problem. I actually believe him because I don't remember the issue when I test drove it.
I'll put a meter on the back of the IGN switch today and see what I get..
Thanks for the input..

[VetteVet]

.......................

Originally Posted by Ironangel

What year of truck do you have? Those two terminals should remain hot during start and run, unless the fuse block or the ignition switch has been molested...? You need to run a new 12ga. wire from either of those two terminals because the original ignition wire is a resister wire only allowing 8 or 9 volts to the old points distributor. The original ignition wire was brown if memory serves correct, discard that wire and run a new 12ga. wire. And yes, if someone tried to run an ignition wire from the ignition switch itself or confuse the purple solenoid wire for the ignition wire then you would only have power while the key is in the start position. Make sure you have a good ground from the battery to the engine block as well as good clean surfaces on the distributor hold down clamp. Theres always some voltage drop during start while the starter is engaged but as long as your getting a full 12 volts to the dizzy while the key is on you should be good to go...

Good advice however I would like to clarify the bolded part.

There is a resistor wire that runs from the key switch, but it is not for the ignition. It is a 24 gauge brown/white stripe wire that runs to the inside of the firewall behind the fuse panel. On the engine side of the firewall block this wire continues to the external voltage regulator as a 16 gauge brown wire.
This B/W wire is needed to provide resistance for the regulator to turn it on to start it charging.



This wire shares the ACC terminal with a 12 gauge brown wire that feeds the fuse panel unless the key switch is pre 68. Then the key switch has no ACC terminal and the wire is tied into the ignition terminal on the key switch. GM installed this wire as a backup to the charging light in case the bulb failed it would provide the resistance needed to excite the alternator. If the truck has all gauges then the wire is the primary resistance for the alternator.


shown here is the brown ACC wire (black arrow), and just below it is the resistance wire for the alternator. The pink ignition wire is just below that. Follow that and it splits to provide voltage to the fuse panel and the firewall block.





As to the coil resistance wire, It is provided by a cloth covered orange/purple/white wire that doesn't begin until the engine side of the firewall block. This wire is joined by the yellow resistor bypass wire from the starter. It is connected to the key switch by a pink wire on the inside of the firewall block using a regular 12 gauge pink wire, that also feeds the fuse panel and the cluster panel. In the earlier years a ballast resistor was used for coil resistance.

Here is the resistance wire shown by the three color wire to the starter.



Here is the wire in real time. it looks like a white wire because the colors have faded from age. The 1 and 3 wires are the oil pressure light and the temperature sender wires.



I wanted to explain this so Badcat would not remove the wrong wires and wonder why the alternator wouldn't charge.

[Badcat]

WOW VetteVet THANKS!! Might take me a while to decipher all that but I'll get on it.
Maybe I should just pay you to drive out to Decatur and help me fix it

[VetteVet]

Originally Posted by Badcat

WOW VetteVet THANKS!! Might take me a while to decipher all that but I'll get on it.
Maybe I should just pay you to drive out to Decatur and help me fix it

Well you really aren't that far from me and I would love to see that gorgeous truck in person. If your only problem is not getting ignition voltage in the start position, then there is an easy work around to fix it. it sounds like IronAngel is right about the ignition switch. It should have continuity between the ignition and start terminals while the starter is cranking. The ACC terminal is the only terminal that is cut out in the starting process. Check to see if the pink ignition wire on the switch ( Ign terminal) is not swapped with the brown and brown/white stripe wire on the ACC terminal.

When you crank the engine with these symptoms it usually won't fire until you let off the key and while the engine is still rolling it will get ignition voltage and will fire up, Maybe!!

If the wires are correct then it's possible that the key switch is faulty. You could replace it and keep the lock cylinder, or you could do the easy work around.

All it involves is running a single wire from the starter R post to the distributor BATT terminal or to the IGN Unfused terminal on the fuse panel.
The R post on the starter becomes hot when the solenoid engages and it sends 12 volts to the original coil for a full 12 volts to aid in starting. All you have to do is tie that into the distributor ignition wire. As soon as the solenoid disengages the R post becomes dead again.

[Badcat]

Some times the simplest thinks can be the most difficult to diagnose. I've had enough cars in my life to have a fair understanding of how IGN wiring works and "a little" knowledge is often a bad thing. Thanks to Ironangel and Vettevet, I was able to confirm my knowledge of the system (and lack of for that matter) and "I think" found the problem.
The truck is wired the way Ironeagle suggested. (IGN UNFUSED direct to coil). Don't remember seeing this before so when I didn't see a wire from the R side of the coil I was baffled.
After tracing every wire I could, and much frustration, I narrowed it down to two intermittent issues. 1) the fuse block connection was loose in side the connector (sometimes it worked sometimes not) 2) The original IGN switch has an internal intermittent problem, if you wiggle the key just so it will lose connection in almost any position.
So, a new switch is on the way and I fixed the fuse block connection..
THANKS FOR THE HELP GUYS!!