Coil voltage?
 

I need some help with coil issues,
I'm trying to start this flathead (1946 59AB) I'm not using any of the cars original wiring except battery cables and starter cable. I'm using an ignition switch from auto store like you would see in boats. I can crank the engine no problem, I have power going to coil (trying to use a modern 70's coil) I have power leaving coil and going to distributor. I don't have power going to the plug wire to the distribor. Should I have a voltage reducer from my ignition switch to the coil? I've tried 4 different coils and can't beleive they are all bad. I've started engines like this in the past without issue but wondering if I burnt these coils up? Any suggestions please.
Thanks, Mark

Re: Coil voltage?
 

Measure the resistance of the coils divide the voltage of your battery(dont know if youre using 6 or 12v) with the resistance you get, that will give you the amps going thrue the circuit if it ends up in the 4amp region your good to go.
Have you checked so your points are opening/closing as they should ??

Re: Coil voltage?
 

I have not checked the points yet because I'm not getting power out of the coil to the main plug wire. Once I get power from the coil I will pull the distributor and set the points (new ones). I will check the resistance this weekend and see what the reading is.
Thanks for you reply

Re: Coil voltage?
 

You won't get anything out of the coil if the points are not working, that is there function:). I would suggest that this might be your problem and not a flock of bad coils! You have to have a way to make and break the current flow through the coil to produce a discharge out of the coil primary wire. You could do this with a piece of wire used to provide a ground and remove it, but I would think it would be a lot easier to just set the point first and then check the coil.

Re: Coil voltage?
 

If you have 6 volts you should use a 6 volt coil 1949 thru 1953 NO resister.

Re: Coil voltage?
 

You can start with checking your coil for proper resistance per this diagram:

http://i1059.photobucket.com/albums/...tion_coil2.gif

If that's OK then bypass the points in the distributor by connecting a jumper wire in place of the low voltage wire that leaves the coil and goes to the points. Also, unplug the high voltage wire from the coil and plug in a spare spark plug wire. Rest the other end of the spark plug wire near a head bolt. Then, with the ignition on and known current to the battery side of the coil, tap the other end of the jumper wire to ground repeatedly. You should see a spark where the temporary spark plug wire is near a ground. If you do, you know for sure that the coil is OK and it's some other problem.

Next, test the points by connecting a test light between the distributor terminal on the coil and the wire to the points. Crank the engine and the test light should go on and off when the points open and close. If so, at least you know they're doing something. May not be exactly right gap but at least they're opening and closing.

Then, hook the wire back up to the coil from the distributor with the temporary spark plug wire still resting near a head bolt and crank the engine. You should see a spark at the end of the spark plug wire. If so, then you know the coil and the points are OK and there is a problem in the distributor cap, rotor, or spark plug wires that is stopping the high voltage current from reaching the plugs.

Good luck and let us know how it goes.

Re: Coil voltage?
 

Thank you George and Prof. that is exactly what I needed to know. No resistor and how to test the coil. I will report back on progress this weekend.

JSeery and flatheadmurre, thank you too for the good tips. I didn't know the points give the signal to the coil when to emit spark out high voltage wire. I thought it was constant power sent to rotor button and when it passed the leads on the dist. cap that allowed the spark to transfer to that designated plug/wire. I'm learning and thanks to all of you guys and this awesome sight.


Mark

Re: Coil voltage?
 

The best thing to do is set it up the way it was originally. That
means rebuilt stock coil, good condenser and the stock resistor.
When set up like original it will be more dependable and if a
problem does happen it's very easy to trouble shoot. G.M.

Re: Coil voltage?
 

I should have mentioned that this is a spare engine I bought that was in a 46 I'm parting. I pulled it last night and now it's sitting on my garage floor. The seller (I beleive is a member on here) states that it did run. I just want to hear it and go from there to determine its destination. Hopefully into the 40 sedan I'm building.

Re: Coil voltage?
 

Pull the spark plugs, lubricate the cylinders and spin with 12 volts to the
starter. Also install a mechanical oil pressure gauge. This will show you
how the rings are and the oil pressure you see is what it will be at 40-50
MPH. It would also be helpful to take a parts washing air gun, put the syphon hose in a bottle of Marvel Mystery Oil and spray in the spark plug holes and down both throats of the carb, turn the engine to open the other valves and spray again. G.M.

Re: Coil voltage?
 

Well, not much progress, I cleaned and gapped the points, confirmed all valves are moving and looked good, also fogged them as suggested. All my coils had resistance like the primary picture posted by Old Henry, none of them had resistance with the secondary test was done as Old Henry suggested. I ordered new points, cap, rotor and wires and will buy new modern style coil locally. I didn't do a compression test but this engine seems good to the ear LOL. Thanks for all the suggestions. Mark

Re: Coil voltage?
 

Are you sure you had the meter on the correct ranges of the test? Primary should be checked at a different range than secondary.

Re: Coil voltage?
 

The capacitor (condenser) in the system is overlooked a lot of times when troubleshooting problems. If it isn't building and holding a charge as designed, the system will be weak with an unstable or non existent spark from the coil primary high tension circuit. Points will fry quickly with a bad one in the circuit.

The last time I tried to start an old motor it sounded OK but would only hit on one or two cylinders. Did a compression test and it had two with very low compression. One ended up having a busted ring with a big blow by gouge in the cylinder wall & piston.