No Spark out of Coil

[BadJoey]

Coil has power going in (+ side) Neg side is grounded at least test light comes on when touched to + side of bat . Has to be a bad coil Right ? Only about 2 years old maybe 1500 miles . Cheap one nothing special . Thanks in advance .

[Chryco Psycho]

the only time the coil should spark is when you disconnect the ground wire . Are you using electronic or points ?

[MEK-Dangerfield]

The coil should have about 1.5 Ohms resistance on the primary side. Anywhere from 8K to 12K on the secondary side. You will need to remove the wire(s) from one side at least to measure resistance.

[BadJoey]

Electronic ignition . I was jumping the selinoid to check for spark . Key was on . Clutch was not pushed in . I know with point cars long as you had juice to coil and points were good you get spark right ?Not sure how electronic works .

[Chryco Psycho]

same thing , key on , power to the ECU & coil the reluctor in the dist sends a signal to the ecu to open the ground on the neg coil wire creating a spark so you can test the coil by connecting the coil to ground & opening the ground circuit & it should fire a spark if it is  then the ECU is bad

[BadJoey]

same thing , key on , power to the ECU & coil the reluctor in the dist sends a signal to the ecu to open the ground on the neg coil wire creating a spark so you can test the coil by connecting the coil to ground & opening the ground circuit & it should fire a spark if it is  then the ECU is bad

Thanks Chryco . Just did this test and got what looks like a week spark out of the coil . Is the ecu bad or might it sill be the coil ? Thanks .

[MEK-Dangerfield]

Some other thoughts. Is your coil mounted vertically or horizontally? Some don't like the horizontal mount.

[dodj]

Thanks Chryco . Just did this test and got what looks like a week spark out of the coil . Is the ecu bad or might it sill be the coil ? Thanks .

ECU only controls when it sparks, not how strong a spark. So I'd vote for a bad coil. 

[Chryco Psycho]

coil will create minimal voltage to jump the gap , widen the gap you get more power , if thereis no sprak while cranking I say it is a bad ECU

[BadJoey]

Now that I think about it , I was getting a lot of spark from the ground wire as I touched the ground to make the coil spark . Although the ecu still looks new I'm betting $40.00 (price of new one)  that's it . Will let you know soon as I get one Thanks

[dodj]

coil will create minimal voltage to jump the gap , widen the gap you get more power

How?

[Chryco Psycho]

It takes increased power to jump a larger gap , a coil can jump 1/4" or more. 
 Go to page 241 & it explains the basics , the coil has a given amount of voltage output available but doesn't use all of it , as condition change , wider gap or higher pressures in the cylinder it become harder to bridge the gap , it will build enough voltage / pressure to create the spark & voltage drops once the spark is created.
 Electricity will always take the easiest path to ground & may not require full voltage to get there .  Electricity is lazy !!
 Increasing the gap too far may exceed the coils ability to make enough voltage to jump the gap & can damage the spark plug wires as well with the extra load they have to carry. GM experimented with this on the HEI systems increasing coil output past 80,000 & increase plug gaps into the .080 -.100 range . Most seem to have dropped back to the .045 -.050 range again

[dodj]

How much voltage is produced at the secondary, as I understand it, is a function of the ratio of the secondary turns to primary turns. It's power output is determined by the initial construction, not the gap at the end of the ignition wire. If the coils output is 50,000 volts, when it jumps the gap, it's 50,000 volts jumping .035 or its 50,000 volts jumping .050. As rpm increases, the primary turns have less time to create a magnetic field, thereby reducing secondary output, but I don't see how changing the gap can change the coils output power.  Again, as I understand it....but always willing to learn, page 241 of what? 

[Chryco Psycho]

forgot to post the link  I will have to go look for it again

[BadJoey]

Well it's not the ecu .If I hook the test light to the neg side of the coil it goes off and on as the motor cranks . Not very bright though (the light or me ) Going to try a new coil today .