Yeah that's basically what the little setup MSD offers isFSJ Guy wrote:One one Jeep I had that I couldn't find a crank and run power feed, I simply used two relays to combine the two and have power on crank and run. You could probably do it with some big diodes, too, but I had the relays lying around and they worked fine.
babywag wrote:One of your DuraSpark box wires should be hot in run & crank. Why not just tap that?
That is the ignition wire source for both of mine.
Single relay, with that wire as trigger on relay.
Sorry I edited my previous post a bit.babywag wrote:The voltage drop is created by a resistance wire, or a ballast resistor, depending on year etc.
There has to be a wire hanging out somewhere that is 12v crank & run.
I vaguely remember converting my '73 to Duraspark from points, and I know it's there.
Sorry, I just saw this post.Dr. Marneaus wrote:Hey Scott! Yeah it's just the 'on/off' 12v lead to the MSD power module not the actual power supply.
Any suggestions would be appreciated.
Sounds like you saying to run a diode between the 12v cranking terminal (I terminal on the solenoid) so that it cannot get power going back to it, and then just add another -2v switched power source? I was thinking about how a single relay would work with two power inputs being connected to each other and didn't think about a diode being used to separate the I terminal from the other 12v source.
I'm not a super big electronics guy so bear with me but it sounds like you're saying with a diode I could run one mechanical relay vs using a dual relay setup or the little MSD relay above.
But then wont the coil constantly get 12v? I thought it was all set up to only give the coil 7v when runningbabywag wrote:If you're going to tap the solenoid for power be sure to remove the resistance wire in the harness if it's still there.
That's why I said to use the DS crank/run wire, it's before the resistance wire (or should be). Or tap into the wire before the resistance wire.Dr. Marneaus wrote:But then wont the coil constantly get 12v? I thought it was all set up to only give the coil 7v when runningbabywag wrote:If you're going to tap the solenoid for power be sure to remove the resistance wire in the harness if it's still there.
"S" terminal (Wire 14) should be full 12V during Start. It should drop to almost 0V with key in run, off or Acc position. This is the terminal post on the starter relay that powers the solenoid coil which pulls in the contact tips.Dr. Marneaus wrote:But my S Terminal is resisted. It only puts out about 7 volts at run.
The DS run wire is only 7v when running.babywag wrote:That's why I said to use the DS crank/run wire, it's before the resistance wire (or should be). Or tap into the wire before the resistance wire.Dr. Marneaus wrote:But then wont the coil constantly get 12v? I thought it was all set up to only give the coil 7v when runningbabywag wrote:If you're going to tap the solenoid for power be sure to remove the resistance wire in the harness if it's still there.