1974 Cj5 Hei Wiring

Hello guys,
Heh I am rewiring the above Jeep (adding an HEI also), and following some You tube video's I added a fuse panel that is powered up via a solenoid when the key switch is turned to 'ON" position. My problem is when the Key switch is turned to "Ign" the panel temporarily loses power since the "On" terminal goes dead temporariliy. So how do I wire the HEI thru the fuse panel with this setup? Do I need to setup a relay that is turned on and provides power to the HEI from the battery direct when the key switch is turned to ignition, but then have another power source from the fuse panel when the key is returned to "ON" position? Maybe I need a key switch that does not lose power at the "ON" terminal when turning the key switch to "Ignition" Not sure so any help would be appreciated. Thanks!

 

I added a fuse panel to mine, but it does not have a solenoid.
The ignition switch should not lose power to "ON" while moving switch to "START".
Catalog (madelectrical.com)
I was going to provide a link to a suitable switch from NAPA, but there are too many styles from which to choose.
1974 Jeep Cj5 Ignitions Switch | NAPA Auto Parts (napaonline.com)

Here's good info that I followed building my new electrical system.
MadElectrical.com - Electrical Tech

 

There is one post on ignition switch that does not loose power when cranking. The “Accessory” post does lose power when cranking.

 

Thanks guys. There is real popular hot rod wiring on YouTube video I think called rescue wiring that lays out a complete schematic but lacks the HEI part and for some reason they are promoting that the fuse panel should lose power temporarily when you go to ignition. I don't know if that's to reduce the load on the battery or? He explains why in the video. I'll just have to look back at it to see why he thought that's the way the fuse panel should be set up. Unfortunately this is how this OEM switch works though.

 

I did find a key switch that does not lose power in the on position during ignition cycle so I think I have the problem solved. Thanks again guys.

 

Not sure which ignition you have,
but,
you should have three posts on the switch. ACC, IGN, and START.

The ACC is on when the key is turned to the left. It runs any time the key is turned there. You would typically run your radio, amps, and any other accessories you wanted to use with the engine off.

The IGN is the first notch to the right and runs anything, including the coil, you want when the engine is on as well as the ACC. You would typically run such things as your gauges through this post. It is dead in the ACC position, however, the ACC post remains hot in the IGN position.

The START position runs the solenoid. It's sole purpose is to crank the engine.

So, in a perfect world, your HEI would be running off it's own solenoid, which is triggered by the stock ignition wire. There should be no need for any added wiring from the switch, as the IGN wire should stay hot between START and IGN.

 

Ignition cycle or START (cranking) cycle?
If it is the cranking cycle, you can run a bypass from the I terminal of the solenoid to the HEI, which will provide power during cranking.

 

I'm pretty sure my key switch is the original key switch. And there's actually four positions. Off then to the right one step for "ON" and then further to the right spring loaded to crank the engine. ACC is in the fully left position past off. My "ON" terminal loses power like I said when the engine is in the crank position. The one I picked up from Carquest, however, does not. So powering my HEI from the fuse panel works fine now.

 

The OEM switch on the back side has terminal outputs and one battery input. Two "ON" position connections, two accessory connections… one battery and one crank. I'll add a few pictures of it when I get back home later. I'll show you a picture of the new switch also

 

Posts. A place to attach a wire.

There is no post for off.

 

Correct - there is no post for off. Here are some pics of the original OEM and my Dorman replacement Thanks for all the help guys!

 

I run my HEI with a standard Bosch relay and a standalone fuse and wire from the battery instead of trying to draw all that power through the fuse block. It's triggered off of the original coil wire.

 

Exactly how I ran my HEI.

 

Be careful guys about explaining the operation of jeep ignition switches. It is an operational fact that several years of early jeeps Ignition switches made the ignition terminal go dead when in the cranking (start) position. The purpose for this was that it lifted all the accessories that were ON removed from battery load and the coil + was wired to the ballast resistor and the (R) terminal of the starter solenoid.