any thing that can go wrong will

[Don Jordan]

I know this is an old story:  "It was running when I shut it off."  (Long story)  I took the engine out, had it rebuilt, put it back in, and now nothing.  No spark to the plugs.  I read some posts about testing the coil.  It didn't say how.  I know I will have to trouble shoot every line.  I just don't know the proper SOP for testing the coil if the motor won't start.  Because the motor is new it's very tight and putting a strain on the battery.

I know this is right out of auto shop 101 but I don't remember ever testing a coil.

thanks for your help,

 

d-

[fhubler]

Well, this isn't right out of a book, just out of experience with old Model A's...  You may be able to pull the boot back on the coil wire on the distributor cap end & rest the end close to the point where it goes into the cap (as close as you can & still see it, and watch for a spark while someone cranks it over...  Just don't touch it while they're cranking...   or do the same thing on one of the plugs to see if you have spark at that point...

[Plymouthy Adams]

testing is described in the repair manual....lot easier to read it there than try to type it here....

[Tubman]

Do you have a multi meter? Set it to the proper "ohms" scale and first test the primary circuit (between the two smaller terminals). It should be in the range of 3 to 8 ohms. Then use it to check the secondary circuit (coil tower terminal to the coil case). That reading should be in the 10,000 to 25,000 ohm range. This is not a definitive test, but a good start. Infinite ohms on either circuit show an open in the coil. No resistance (zero ohms) show a short. If either of these conditions exist, beg, buy ,or steal another known good coil.

[Pete]

Hi Don,

Assuming the engine cranks: The easiest way to test the coil secondary wiring is to use a timing light. Put the inductive pickup on the HT lead from the coil to the distributor. Crank the engine and look for STEADY light flashes.

Pete

[John Reddie]

If you are using a point type ignition system, this is what I did once. Removed the distributor cap and turned the engine over so the points were closed. I removed the coil secondary wire from the cap but left it plugged into the coil tower. Turned on the ignition switch and while holding the end of the coil wire with insulated pliers about a quarter of an inch for a good clean ground, opened and closed the points with a screwdriver. You should see a nice fat spark jump from the end of the coil wire to the ground. If you don't or the spark is  very slight, then the coil could be the trouble. I was fortunate to have a spare coil on hand and when I hooked it up, the engine started and ran great. Good luck to you.

John R

[Plymouthy Adams]

this can tell the coil is good, but can bypass a high resistance set of point that could ultimately be the real failure...using a nonmetallic object to open and close the point will reflect the condition of the breaker points surfaces as they meet...

Edited November 28, 2017 by Plymouthy Adams

[Don Jordan]

it's not easy going through life really stupid.  Checked the coil and it was okay.  Pulled the dist. out - there was a very little wire, the insulation had worn off just enough to ground - I'm going to put it all back together tomorrow and hopefully be able to get it started.

For all of you who pitched in thank you.  It's always something small.  "For the wont of a nail the shoe was lost..." 

[pflaming]

"Something small" how true! I could not get my new alternator to work, when I hit ig I fried wires, so disconnected it. A good friend, a mechanic looked at it yesterday. I had the wires connected to the brush bolts!!!  DAH!

[jhm1mc13]

Did you change the condenser?  Try and find an American one as the Chinese replacements are poor. 

[pflaming]

We put a meter on it today and it is charging according to the book. 

[Silverdome]

Murphy is always lurking in the shadows and will follow you around silently like a cat on the prowl then pounce on you when you least expect it. He is nobody's friend.

[pflaming]

I thought Murphy's cat died in my shop fire! 

[Plymouthy Adams]

4 hours ago, Silverdome said:

Murphy is always lurking in the shadows and will follow you around silently like a cat on the prowl then pounce on you when you least expect it. He is nobody's friend.

Murphy came a calling last night, my coffee pot went belly up.....had to break out the percolator this morning....back on line tonight with a new drip model...got no use for Murphy