Thread: no current over coil

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After breaking in the engine this morning, I turned the car off. Then it would not restart. There was no spark. With the ignition switch on, I could not find any power on the pos. and neg. sides of the coil. (I no longer have the HEI, but a seperate coil, feeding a eletronic distributor - but not an HEI type) I took the coil to a store, who tried to test it, and determined it was not up to par. I had 19 volts on the pos. side of the coil, at the ignition wire connection, using the neg. side of the alternator as the ground to test the pos. side of the coil. Soooo, I got a new coil, and had the alternator tested, and it was fine. The store replaced it anyway. Soooo, with a new coil, new alternator, I still get 19 volts on the pos. side of the coil, still no current across the pos. and neg. of the coil with the ignition on, and still no spark! Everything worked fine this morning and has since we put the engine back in the car. It's hard to imagine that this new coil is bad. And why would the alternator show 19 volts coming out? Hellp. Thanks - kip :-? Just to clearify - there are 19 volts across the battery terminals, and thus 19 at the back of the alternator...

Sorry if I am simplifying stuff here, but you do know how a coil works, dont you? Putting any DC voltage on a coil will result in zero output. A coil REQUIRES that you have a expanding/collapsing field to work. In a points distributor, the points act as the "interruptor" to cause the field to collapse when the points open and the field to expand when the points close. This alternating action causes the magnetic field to induce voltage to the output windings of the coil..... the voltage output is the product of the input voltage X the winding ratio X some efficiency number.

How did you test the coil?

By the way, an alternator output should be about 14.7 volts, certainly not 19. What are you using for a voltmeter?

Test your battery voltage with the motor off. You should read somewhere in the 12 VDC to 13.5 VDC range. If it is higher, you have an optimistic voltmeter....make sure it is on the DC scale.

If you put an ohmmeter across the + and - terminals of a coil, you will read what is called the primary resistance. If you put you ohmmeter across the secondary terminal (the big wire to the distributor cap), you will not see continuity to the + coil terminal because the primary and secondary windings are not connected.

The distributor is a Procomp Electronic distributor, so there are no "old fashion points" in it; and of course it uses a separate coil. I did not think about the voltmeter being messed up, but it has had its share of drops and such... to test the coil I took it to an auto parts store, and they tested it with a voltmeter across its various terminals, and it read less than it should have. Should there be a voltage reading across the coil's positive and negetive terminals with the ignition on? I'm guessing the answer is no, unless the engine is running... Tomorrow I'll get a new voltmeter and test the readings. But, the deal is, it still will not start, because there is no spark at the plugs... thanks - kip

Take a plug wire and stick it in the coil tower,put a plug in the wire and lay it on the block so the threads are grounded. Now turn the key on and off,if the coil is good you'll get a spark every time. This being so,your ignition fault is in the distributor. If your alternater is putting out 19v,you've got a bad regulator. Hope this helps you,Hank

Rather than replace parts willy-nilly, test the voltmeter first!! Place it across the battery terminals with the engine off...it WILL NOT read 19 volts unless it is really a bad voltmeter OR you have it on the wrong voltage setting.

Have the alt. tested at the auto parts store. Good or bad you still have no spark, one easy thing to try disconnecting the Tach. line and see if you have spark. If so you have a short in the tach line, if not drop in a spare distributor. I think this is were your problem is.

Certainly you have two problems. The 19 volts could be a voltmeter problem. The spark issue I have had a similar problem. Runs good and you shut it off and never to start again. Voltage to the distributor but no spark. Sound familiar? My problem was that the distributor grounds itself to the block. The problem is you use of gasket to keep the oil in around the distributor hole. This gasket can isolate the electrical ground. Now you must rely on the hold down bolt. Bottom line - I ran a ground wire from the underside of the distributor to the block. Solved my problem.
Let us know how you turned out.

Another possibility is that you are misreading your voltmeter---19 volts isn't a reasonable number in itself, however if you have an auto ranging digital meter you could be misreading 1.9 volts which wouldn't be suffienct to operate the ignition----I hate the auto range meters, especially when reading ohms

At 19 volts something might blow if not fixed. Had that problem on a trip once. One wire alternator, regulator went nuts and over charged, battery exploded, wires melted. Not pretty. Check voltmeter, the alternator/regulator, all grounds and other key parts.