Hey everyone, I have what appears to be an electrical gremlin. The symptoms include:

*High speed miss. Started at around 7000RPM, then 5000RPM, then 6000RPM.
*Random instances of shutting the car off with the ignition switch and the car doesn't shut off unless I flip the master disconnect switch. Then it acts normally again.
*Random instances where I turn the ignition switch on and it takes a few seconds for it to actually power on. Also a delay when shutting off the car.
*Tachometer randomly jumps upwards of 400 to 500 RPM.

I've changed the following making one change at a time: Coil, plugs, plug wires, ignition box (from 6AL/2 step module selector to 6AL2), master disconnect, ignition switch in the switch panel, distributor, cap, rotor, master disconnect. I've unplugged/disconnected the alternator as well. Checked all grounds.

Car was rewired several years ago. I do see one ignitor wire on the fan relay that has gotten hot and intend on replacing that relay (fan still works).

I'm running a 6AL, however the miss was still there when switching to a 6AL2 which eliminated the 2 step module selector.

I'm planning on throwing a different tach on the car as I'm wondering if there's some sort of feedback through the tach to the ignition box.

Any advise on how to attack this issue?

This message has been edited. Last edited by: David_D.,

Well, it is a little late to tell you to change / replace one thing at a time, sooooo.......

Run on with the ign. switch off is usually related to the alternator feed not having a diode, but I have no clue how much O.E. wiring you're using. ?

Yes to unplugging the tach, usually that is the first thing to do.

Ignition on / off delays?
Are there relays involved?

We need a LOT more information.

You mentioned you changed the ignition switch, but did you change the wires to it as well?

If you’re using a K&R wiring panel, I’d try taking that out of the equation and run a separate switch to the ignition for testing.

What brand/ model relay panel and toggle switch panel are you using?

quote:

Originally posted by Goob:
Well, it is a little late to tell you to change / replace one thing at a time, sooooo.......

Run on with the ign. switch off is usually related to the alternator feed not having a diode, but I have no clue how much O.E. wiring you're using. ?

Yes to unplugging the tach, usually that is the first thing to do.

Ignition on / off delays?
Are there relays involved?

We need a LOT more information.

I did replace one thing at at time. Updated post to indicate that.

I've run all new wiring, however I'll have to check if I used a diode on the alternator wire. It's a two wire alternator. This issue just started happening out of nowhere, and the car was re-wired several years ago.

This message has been edited. Last edited by: David_D.,

quote:

Originally posted by markemark:
What brand/ model relay panel and toggle switch panel are you using?

It's a panel that I built myself. I can't remember exactly what brand relays I used on this panel, however I generally use PICO brand.

The switch panel is a Painless and it's been in the car for quite a while.

This message has been edited. Last edited by: David_D.,

Change/Add grounds. Same thing happened to my wife's car a few years back. Changed/swapped everything. Drove me crazy, car worked fine for years then started having a miss. I changed and added grounds EVERYWHERE from directly off the battery including added them to BOTH cylinder heads. The next weekend the issue was gone.
Don't know which one ground fixed it but it didn't matter at that point.

quote:

Originally posted by David_D.:It's a panel that I built myself. I can't remember exactly what brand relays I used on this panel, however I generally use PICO brand.

The switch panel is a Painless and it's been in the car for quite a while.

The only item you did not list replacing was the relay that the ignition ON switch is wired to (ignition ON relay). Was that relay replaced?

quote:

Originally posted by markemark:

quote:

Originally posted by David_D.:It's a panel that I built myself. I can't remember exactly what brand relays I used on this panel, however I generally use PICO brand.

The switch panel is a Painless and it's been in the car for quite a while.

The only item you did not list replacing was the relay that the ignition ON switch is wired to (ignition ON relay). Was that relay replaced?

That is correct. I don't have the switch panel powered through a relay.

Sounds Simple....But check your Battery Cable connections..Clean, bright and shiny and tight..
Replace the Battery if you have a good test one available....Have seen Bizzare issues with Batteries...Have seen good techs tell me the Cable Connections were good....and they were crap

quote:

Originally posted by David_D.:

quote:

Originally posted by markemark:

quote:

Originally posted by David_D.:It's a panel that I built myself. I can't remember exactly what brand relays I used on this panel, however I generally use PICO brand.

The switch panel is a Painless and it's been in the car for quite a while.

The only item you did not list replacing was the relay that the ignition ON switch is wired to (ignition ON relay). Was that relay replaced?

That is correct. I don't have the switch panel powered through a relay.

NOT the switch panel being powered through a relay. I’m talking about what relay feeds the ignition ON for MSD, tach and whatever else it’s tied to. Does the Ignition ON switch not power a relay??

I have a fuse block that is powered directly to the battery, and a fuse block that is powered by ignition switch ON. Neither of those are through a relay. All of my accessories are triggered through relays.

I think I need to be looking at anything that can feed back to the ignition box. As stated, I'm going to replace the tach with an older unit I have here. I've heard of faulty tachometers causing issues.

quote:

Originally posted by S/S Dart:
Sounds Simple....But check your Battery Cable connections..Clean, bright and shiny and tight..
Replace the Battery if you have a good test one available....Have seen Bizzare issues with Batteries...Have seen good techs tell me the Cable Connections were good....and they were crap

I've also heard this about batteries. I'll plan on switching it out as a test.

Remove the wires from the alternator and see what it does. The delay when you turn the ignition on and a delay shutting off doesn't make sense. What are you using for an ignition switch? 6AL should have a heavy power wire direct to the battery power and a heavy ground direct to battery ground, no other junk on that line has to be clean. Ignition switch just triggers the 6AL box to turn on.

any battery or power wire that is soldered and in heat shrink can cause issues if the solder joint goes bad.been there done that.

quote:

Originally posted by David_D.: I have a fuse block that is powered directly to the battery, and a fuse block that is powered by ignition switch ON. Neither of those are through a relay. All of my accessories are triggered through relays.

I don’t understand how this is wired and would need to see a diagram to make sense of it. This being your design, you have more knowledge of it.

The statement below from your initial post is the part that is the most confusing and I’m guessing goes back to the Ign ON wiring method.

*Random instances of shutting the car off with the ignition switch and the car doesn't shut off unless I flip the master disconnect switch. Then it acts normally again.

Do you have a relay triggered by the ignition switch that is powered by the battery? Possibly that is backfeeding???

What alternator are you running?

quote:

I'll have to check if I used a diode on the alternator wire. It's a two wire alternator.

If it's a Delco style, you need to replace the regulator with a one wire style, or, the diode that comes with the MSD must be installed in the ignition feed to the regulator to prevent the run on. But not always, it's hit and miss.

quote:

Originally posted by Goob:
What alternator are you running?

quote:

I'll have to check if I used a diode on the alternator wire. It's a two wire alternator.

If it's a Delco style, you need to replace the regulator with a one wire style, or, the diode that comes with the MSD must be installed in the ignition feed to the regulator to prevent the run on. But not always, it's hit and miss.

I’ll check the wire that needs the diode to see if I have one installed.

quote:

Originally posted by Eman:
Do you have a relay triggered by the ignition switch that is powered by the battery? Possibly that is backfeeding???

I have several relays powered by the battery when the ignition is on. They aren’t triggered until I turn on the accessories that they power. I need to test those relays for failure.