Continuity from both side of coil to ground. Not good, right?

[pktaske]

No spark on my 2.5L Chevy Merc. I've tested both sides of my coil and have gotten continuity from each post to the engine block (!?) I have just replaced my alternator but I think the problem was from before I did this.


Also what is the small black wire running from under the distributor to the bow side coil post?

Thanks...and if anyone can recommend a post hear to read through thats pretty comprehensive around testing the ignition system on a 2.5L. I would greatly appreciate it.

 

[thumpar]

Re: Continuity from both side of coil to ground. Not good, right?

Test for ohms. Most meters will beep on anything close to 0 so you need to find out exactly what it is.

 

[rodbolt]

Re: Continuity from both side of coil to ground. Not good, right?

ok, draw a simple switched circuit, go from the coil primary + post, through the primary windings(very low resistance by the way) then from the ign coil primary post down the black wire to the points. remember the points are simply a mechanically driven on/off switch.
switch open no continuity,switch closed continity to ground via the dist body.
there is your answer
open the points and the resistance will change dramatically, if it does not,check the condenser(blocks DC passes AC.
remember when running the peak voltage rises to about 160VDC and falls to roughly 0VDC rapidly.
the condenser sees this as an AC(rapidly changing) voltage and acts accordingly by charging and discharging thus aiding in absorbing the ringing effect of the ign coil(inductive transformer). if the condenser is shorted it bypasses the points(on/off switch) and you never get a collapsing field in the ign coil primary.
I prefer voltage tests, with points open you should have close to battery voltage on the coil primary terminals and close to 0 v when points are closed.

 

[pktaske]

Re: Continuity from both side of coil to ground. Not good, right?

Thanks for the clarifications.

Any idea where I can get a schematic?

How can I tell if my coil is bad? Could it by my points? I'm going to pull off my disty cap and take a look now.

 

[pktaske]

Re: Continuity from both side of coil to ground. Not good, right?

Also - I can get points and disty cap from NAPA? Anything special about them if I plan to change them each year?

 

[pktaske]

Re: Continuity from both side of coil to ground. Not good, right?

FOLLOW UP - replaced points, coil, cleaned up terminals all over the place and she runs like a charm. Alternator is working now too. At last.