Verify coil

-
Backally

Backally

FABO Gold Member
FABO Gold Member
Joined
Sep 4, 2011
Messages
631
Reaction score
401
Location
Wisconsin
70 Duster. Chasing down an issue, think it’s my Holley Sniper but want to eliminate any ignition issue. With key in run, I got 12v at the blue Wire going into the ballast resistor. How much voltage should I have on the other side, and is that the same as the coil + stud?
 
And off the coil +, would this possibly be a ballast resistor problem?

3226082D-54E0-4FB0-ADD7-C747A222F721.jpeg
 
I would guess so, but it may be something else, wired wrong, etc

Did it ever run?

Are you sure you don't have "something else" hooked to the coil + side of the ballast? That would load the reading down
 
67Dart273 said:
I would guess so, but it may be something else, wired wrong, etc

Did it ever run?

Are you sure you don't have "something else" hooked to the coil + side of the ballast? That would load the reading down
Click to expand...

Man, this has been killing me for a month. Long story, try to make it short. Put Holley sniper on last winter. Was running great for 6 weeks, then became inconsistent, would run great then die. Start it would sound like it’s on 5 Cylinders. Next day run great. Holley thought rfi so I rerouted wires. Had a thread a couple weeks ago about how I had it hooked up to ign 1 & 2. So tried starting it today and it won’t run. Power to the handheld is good, which shows 12v from ign 2 when cranking, ign 1 when in run. But Sniper is not showing rpm so it shuts down immediately after the prime shot is burned. So is coil not getting enough voltage in run to keep it going? It may be the efi, I’m trying to eliminate ignition from being the issue

Ballast resistor ohm checked at 0.8, which is what the msd coil calls for.
 
As I said earlier check carefully that nothing accidently got wired to the coil + side of the coil. Is this factory wiring?

Another thing to check is that the factory coil bypass is hooked up correctly. It is the brown wire tied into the coil+ side of the ballast, goes through the bulkhead connector, and to the IGN2 terminal of the switch. It is even possible that the switch itself is AFU

What exactly is hooked to the coil plus and minus terminals?
 
67Dart273 said:
As I said earlier check carefully that nothing accidently got wired to the coil + side of the coil. Is this factory wiring?

Another thing to check is that the factory coil bypass is hooked up correctly. It is the brown wire tied into the coil+ side of the ballast, goes through the bulkhead connector, and to the IGN2 terminal of the switch. It is even possible that the switch itself is AFU

What exactly is hooked to the coil plus and minus terminals?
Click to expand...

I wish you lived closer, I’d throw a big chunk of beef on the grill and pick your brain for an hour.

As far as I know factory wiring. But some things don’t jive with the wiring diagram I got. I got a black wire with a yellow trace going to the coil +, my diagram says it should be dbl. Negative is dark blue, along with a wire to the sniper that tells it the rpm. Wiring diagram says it should be gry/tracer. My distributor has a blue wire and a grey/blk wire, my diagram shows 1 unlabeled wire. My ballast resistor has a light blue/y and a dbl, wirei g diagram shows only the dbl. it looks factory. It ran fine the 8 yrs I’ve owned it. Ran fine beginning of this year. Just this last month it’s gone downhill.

I do have the snipers trigger wire connected to ign 1 and 2. It needs power both while cranking and running and I didn’t know where else to get it. But like I said, it ran fine for first 6 weeks of this year so I am assuming it was ok.
 
Last edited:
Trash can the ballast resistor and go with a HEI setup. One of the best things you can do with these cars. Google it up you will be a happy camper

F13A2A70-DA6F-4DF0-8911-6471FAF60EE4.png
 
If it is a points system and the point happen to be closed when you check the voltage it will be dropped. Just an idea
 
If I got 12v going into the ballast resistor, what should I show coming out with the ignition on run?
 
Backally said:
If I got 12v going into the ballast resistor, what should I show coming out with the ignition on run?
Click to expand...

Somebody mentioned "if it is breaker points." That is a good point

Key in "run" points open: Should be same as battery on both sides of ballast resistor and on coil plus and coil minus

Key in "run" points closed: Should be nearly same or same as battery on "key" side of ballast and coil PLUS side should be anywhere from 5 lowest to maybe 9, highest. This depends in part on the type of coil.

Coil MINUS with points closed will be a small voltage, 1/4--1 volt

Key in "start" Coil PLUS side of ballast should be "same as battery" during cranking and should be at LEAST 10V or higher
 
MSD pro-billet dist, orange box, MSD blaster 2 coil. Ballast resistor ohmed.8, which is what it’s supposed to I believe. I get the same voltage coming out as going in, I thought it should be less but idk.
 
Backally said:
MSD pro-billet dist, orange box, MSD blaster 2 coil. Ballast resistor ohmed.8, which is what it’s supposed to I believe. I get the same voltage coming out as going in, I thought it should be less but idk.
Click to expand...

This is confusing. "same" where in/ out? Under what conditions? Are you saying that both ends of the ballast (key in "run") are 1.4?

What is this "orange box?" You running an Mopar orange box with an MSD distro?
 
Here is the deal.........Mopar ignitions draw coil current with engine stopped and key in "run." So "what I would expect" at the ballast is "same as battery" very close to 12--12.6 at "key side"

Coil + should be somewhere from 6--9v depending on type of coil. A "hotter" coil might show less than OEM because they draw more current

Coil neg should be quite low perhaps 1-1.5V
 
You must log in or register to reply here.
-

Back
Top