power to coil

I just put a fresh 304 in my 79 CJ5 and I can't get it to start. I checked the voltage to the coil, with the + wire disconnected from the coil I have around 12.5vdc on the wire. With it connected to the coil I'm reading around 6.5vdc. Those reading are on the + wire coming off the solenoid. Does the coil draw the voltage down that much or is it posible the coil is bad. It worked on the old 304. I'm taking these measurements with the key on. No I haven't checked for spark yet, I have no help to turn it over while I check a plug wire, I may have to get the wife out here.

 

I'm not quite understanding your wiring setup. Are you saying you have a wire running from the + terminal of your starter solenoid to the + terminal of the coil ? If so that wire would always be hot and and be independent of any switched supply.
The wire that is connected to the coil on my 75 comes from a switched source and reads normal voltage with the key on and no voltage with the key off.

 

If you want to crank the engine from outside the vehicle you can build a remote starter switch by simply using a short length if wire jumping from the + side of the starter solenoid t one of the small terminals of the solenoid.

 

With the wire hooked up you have to know if the distributor points are open or closed to get a proper reading.

 

I thought the positive wire to the coil came from the solenoid, maybe not. Anyway I still only have 6.5VDC on it when its hooked to the coil, but 12 if I disconnect it from the coil. I do have the engine at TDC while doing this. It doesn't have points, it has a module.

 

Try running 12 volts stright from the battery to the coil. See if it starts. You need 12 volts could be a bad coil.

 

Wire to the coil from the sol is only for power while cranking. With the key in the run position power comes from the switch through a ballast resistor if it has one, if no bal/res then just from ign switch. Depends on which igniton system you have wether you have a ballast or not.

 

If its HEI, pull a plug, roll it over and look for spark. no spark = bad coil, or bad coil ground.

Otherwise just pull the coil wire off the top of the distrib and ground it during rollover. Look for spark. Easy diagnosis.

One of the common mistakes with a fresh swap is getting TDC 180 degrees off. If you have spark, make sure both valves are closed on #1 cyl at what you think is TDC by looking under the tappet cover. If exhaust or intake is open, your 180 off. Sometimes what you think is TDC, is off.

 

Thanks guys. I'll pulled valve cover, both valves are closed. I thought maybe bad ground so I ran a ground direct from battery to neg side of coil, still only measure 6.5 volts accross coil. Does anyone know what the ohms reading should be accross the neg and pos of the coil with the wires unhooked. That should tell me if the coil is bad. Something is drawing it down in voltage.

 

Electronic ignition coil is triggered by the module. Dont connect battery pos to coil plus and the coil neg to bat neg you will burn wires and or coil. the coil neg should be going to the module. Is that what you have?

 

You need the serivce manual on page 1g for ignition system tell you step by step. does it crank over but doesn't start . on step 4 it say to replace the starter solenoid.