i have a 1947 ****** jeep with a 302 two barrel in it.im having ingnition problems with it. i put as new coil and ignition switch and cap and rotor.it turns over but im still not getting any spark.theres two small posts on the coil with a neg and pos marking, which one goes to the cap and rotor and witch one to the key.i also installed a new seloniod.can anyone give me a fast run down of what goes where. there is no other wires in the way because the truck is stripped so i dont have a mess i just need to know what goes where so i can get it fired up. thank u

 

On the coil, the positive terminal goes to voltage (the starter switch). The negative terminal goes to the distributor. Pull the positive wire off the coil and turn on the key (for voltage only-you're not actually trying to start it), and see if the wire reads 12 volts. If not, the problem is somewhere around the ignition switch. If so, put the positive wire back on and remove the negative wire and read that coil terminal, again with the switch on, to see if theres voltage there. If not, the coil is bad (can happen even with new ones). Open the distributor and see if the cam is actually lifting the points as it spins. Turn the engine by hand until a cam lobe is under the points and see if the points lift. The hold down screw can slip and if the points arn't opening then no spark. If the points are opening (say at least .017") then see if there is a condensor connected to the points and check it for shorting (if it is, replace it).

The problem should show up with one of these checks. Back to the start; if you're not getting juice to the positive coil terminal, theres a problem somewhere in your ignition switch wiring. Also, some vehicles take ingition voltage from the starter relay during actual starting (or use resisitors in line), then revert back to direct ignition switch feed while running. To check this, remove the positive wire again and read for voltage as someone turns over the engine. If the voltage drops top 0, that's the problem. Otherwise, trace back the positive wire to the switch, or where ever else it might go, looking for shorts, disconnections, etc. Hope this helps.

 

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ok i have power to the coil,and i have power to the rotor and points and they have spark,but i still dont have spark to the plugs.but i did put in a new cap and rotor,the only thing i can think of now is that maybe the top of the rotor is not making contact with the coil wire.thanks for your help. angelo

 

You might want to take off the cap and rotor, and place the rotor underneath the cap centered, as if both were sitting on the distributor, and then make sure the gap between the rotor end and each of the distributor contacts is narrow enough for a spark to jump across. I once bought a cap and rotor for my 351W, and wound up with a rotor for a 6-cyl. The rotor to distributor gap was a good half inch.

Could you clarify what you mean when you say you have power to the rotor and points? On a breaker-point system, the points act as a switch to ground, which is why they go to the negative on the coil. When the points open, the coil loses its ground and the primary winding finds the next ground, which is through the plugs.

Also, make sure you have a good grounding wire in the distributor. There should be a small length of wire within the housing that connects the top part of the breaker plate to the distributor housing somewhere--this grounds the points.

 

What I do to check for spark on a point ignition system is to pull the coil wire out of the dist. cap, leaving the other end in the coil and then remove the cap. Make sure the points are closed, grab the coil wire well back from the bare end and hold it about 1/4 inch away from something bare metal on the engine and open/close the points with a thumbnail. Each time they open you should get a nice blue spark jumping between the coil wire and ground. If so, but there's no soark at the plugs then look closely at the cap, rotor and wires. The spark will take the path of least resistance, so if everything is up to snuff it should be the normal path through the rotor, cap and wires.

If it makes you nervous to hold the coil wire while doing this you can hold it lightly with insulated pliers or a plug wire puller if you have one.

But real men use their bare hands...

 

Try pulling the coil wire out of the center of the distributor cap and wedging the tip near (say 1/4") the block. Crank the engine, and if you get spark you'll know that the coil and points are working, and there may be a problem with the rotor/cap or maybe ancient resistor plug wires. If you get no spark from the coil wire then the problem is still in the coil or distributor (refer back to fmc400's post).