Starting Problem

[Bob Malone #35242]

How do you test a coil?

Thanks Wayne, I found the MSD troubleshooting page last night and guess what..., therein lies my problem. My wipers do work with the ignition in the "on" position. What I don't know is if I have a bad coil. How do you test a coil?

[Bob Malone #35242]

How do you test a coil?

Thanks Wayne, I found the MSD troubleshooting page last night and guess what..., therein lies my problem. My wipers do work with the ignition in the "on" position. What I don't know is if I have a bad coil. How do you test a coil?

[Wayne C.]

Re: How do you test a coil?

A (disconnected) coil is tested with a multimeter by reading primary resistance (across the + and - terminals after cleaning them up thoroughly with emory cloth to get a good contact), and secondary resistance by reading from the coil wire receptacle to either the + or - terminal. One problem is that you need to know what those readings should be in ohms for YOUR coil. I do not know. Primary resistance in a stock coil is usually quite low, in the 1 to 2 ohm range, while secondary resistance is quite high, perhaps around 7500 to 10000 ohms. Unfortunately this static test won't always tell you if the coil is working properly. Since your car fires up with the key in the "start" position, I would be disinclined to suspect a coil problem... something in that MSD system does the job of the original ballast resistor. Unfortunately I am not conversant with MSD ignitions; how far did you get into the MSD troubleshooting checklist?

[Wayne C.]

Re: How do you test a coil?

A (disconnected) coil is tested with a multimeter by reading primary resistance (across the + and - terminals after cleaning them up thoroughly with emory cloth to get a good contact), and secondary resistance by reading from the coil wire receptacle to either the + or - terminal. One problem is that you need to know what those readings should be in ohms for YOUR coil. I do not know. Primary resistance in a stock coil is usually quite low, in the 1 to 2 ohm range, while secondary resistance is quite high, perhaps around 7500 to 10000 ohms. Unfortunately this static test won't always tell you if the coil is working properly. Since your car fires up with the key in the "start" position, I would be disinclined to suspect a coil problem... something in that MSD system does the job of the original ballast resistor. Unfortunately I am not conversant with MSD ignitions; how far did you get into the MSD troubleshooting checklist?

[Bob Malone #35242]

Re: How do you test a coil?

Wayne, thanks again and I'm sorry it took so long to respond. I've been gone since Friday morning to the Texas Hill Country with a bunch of Harley buddies for the annual spring wild flower ride.
I got as far troubleshooting the MSD determining if the coil is good. I have a new coil but I don't remember what it's for and it didn't start with it either. I ran out of time but now I'll check to see if I have 12v on the red wire. I'm suspecting I have an MSD that's gone bad. It did that once before when I had the car in the shop for six months (don't ask why it was in the shop six months, thats a real sore subject with me.)

[Bob Malone #35242]

Re: How do you test a coil?

Wayne, thanks again and I'm sorry it took so long to respond. I've been gone since Friday morning to the Texas Hill Country with a bunch of Harley buddies for the annual spring wild flower ride.
I got as far troubleshooting the MSD determining if the coil is good. I have a new coil but I don't remember what it's for and it didn't start with it either. I ran out of time but now I'll check to see if I have 12v on the red wire. I'm suspecting I have an MSD that's gone bad. It did that once before when I had the car in the shop for six months (don't ask why it was in the shop six months, thats a real sore subject with me.)