73 cj5

You forgot to answer the question....

Does it 'run' as long as the starter is turning and then die when the key goes to 'run' or not?

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

KC wrote:

That vintage shoud have a ballast resistor. The issuie here is simply that you have no power to the coil when the key is in the "ON" position, opnly when it is in the "start" position. YTou need a wiring diagram showing the starting circuit for that MY & powertrain. Then you need to replace the missing wiring.

Did this friggin' thing run before you bought it? If so, what happened afterwqards? In other words, what repairs or mods were done that caused this problem?

I'm pretty sure that he said that he doesn't have the ceramic resistor, but rather the OEM resistive wire spliced into the harness.

In any case, KC should measure the voltage at the [+] terminal at the coil with the key switch in the "run" position.

That is a failure in the ballast resistor wire or it's circuit or a dead ignition module or a screwed up ignition switch wiring....

If you don't have an ignition module, then the ignition switch is next likely, but only 5 volts on the coil power when the key is in run could be an issue all its own. There is a crimp connector where the ballast wire and the wire from the starter solenoid join. They fail over time and you might just have one thread left, enough to tag some volts, but not pass much power or load.

You can take a wire and tag the coil positive from the battery direct and see if it runs. If it does, then you need to trace wires. This is fine for test running, but be sure and disconnect the wire when stopped or the coil can cook.

Oh, make sure you are checking the correct side of the coil for the power. One side will read 9 volts or so and the other can read (ground side) 4 volts or so.

The ignition switch has a direct battery connection through the starter solenoid main battery wire bolt and a fuse link wire.

When the starter cranks, the side post from the solenoid sends power to the coil.

When in run, the red wire with the white stripe from the switch sends power via a crimped in ballast wire. The ballast wire starts around the brake master cylinder and runs inside the harness loom over close to the coil. The coil end of the ballast wire is where the solenoid start wire hooks in.

Mike

KC wrote:

One more thing, if you have the GM alternator, unplug the plastic 2 wire plug and see what happens. Sometimes they can short inside and ground the excite wire (small solid core, usually a brown one) that tags the coil power line killing the run power.

Mike

Mike Roma>

You do (should) have a resister wire instead of a ballast resister on a '73. It is shown on your wiring diagram. Turn your key to the "run" position (where it would be driving down the road)and check voltage from your "+" on your coil to ground. It should be in the 8 volt area. If no voltage is present then you should look at things up stream of this supplying resistor wire like your ignition switch. Are there any other wires on your "+" coil terminal? I got into one that had the "+" for a tach, the "+" for an electric fuel pump, and the "+" for the electric choke anchored to it. Not only does this drain away some voltage it also only gives 8 volts to things that want 12 volts. As Mike kind of said you could buy a ballast resistor and run a hot wire with it in series just to see if it would run. This could also point you up the harness to the ignition switch. Good luck!!

You can run straight 12 volts to the coil for testing purposes.

I just noticed this thing has an external regulator, if that isn't wired right it will pull the coil power to ground too.

That's a yellow wire from the starter solenoid to the regulator. It can be disconnected for testing purposes.

Mike

cj573cj5 wrote:

I just noticed this thing has an external regulator, if that isn't wired right it will pull the coil power to ground too.

That's a yellow wire from the starter solenoid to the regulator. It can be disconnected for testing purposes.

Mike

Mike Roma>