Maybe I can help you guys out here. I have three of these cars in my yard including a '78 model.
You never stated what the problem is. I assume from reading what you're trying to do the engine does not crank when you turn the ignition switch. This is a real simple, basic, straight forward system. It would be easier to diagnose and repair it than trying to jump stuff, but if that's what you want to do, how to do it still depends on what's wrong. You have to jumper / bypass / short together something that is going to bypass the problem. For example, the neutral safety switch is on the lower rear left side of the transmission but bypassing it up on top won't help if that isn't the problem.
Some information that will help us includes:
Do you hear a light single click under the hood when you turn the ignition switch to "crank"?
Do you hear one kind of loud clunk from the starter but it doesn't spin the engine?
Do you hear a rapid succession of clicking, almost like a loud buzzing noise when you try to crank the engine?
Do the dome lights or head lights stay bright or go out when trying to crank the engine?
All of these have different causes and can lead to a solution. If the battery and cable connections are fine and there is just a problem in the starter system, rasmataz was trying to explain how to bypass the starter relay. The whole system can be broken down into three circuits. The tiny-current circuit goes through the ignition switch and neutral safety switch to activate the starter relay. The relay contacts are part of the medium-current circuit that passes about ten amps of current to the starter solenoid which is built into the starter. That solenoid activates the switch in the starter that passes the very high current to the starter motor, about 150 amps. So, the key switch uses a little current to turn on the switch that passes a medium current to turn on the switch that controls the high current.
It's not practical to bypass the high-current circuit. You'd need a huge cable and would burn your fingers. There isn't much in that circuit anyhow. The tiny-current circuit doesn't cause much trouble, at least not on most Chrysler products of that era. The most common way to get a dead starter circuit to crank the engine is by bypassing the starter relay contacts. Be sure the transmission is in "park" because you will be bypassing the neutral safety switch too. You'd look silly running after the car if it started in gear! Smile
The starter relay is a metal box that is bolted to the firewall just next to the driver's side hood hinge. It is about 1 1/4" by 2" and will have four terminals for sure, possibly five. Two wires could be bolted on or they could all be plug-in type connectors. The style changed somewhere in the mid '70s but the wires are the same. To do yourself what the ignition switch normally does, you want to jumper the two fat wires on the relay. The one coming from the battery will be red and the one going to the starter solenoid will be dark brown. Speaker wire will work but a better choice is a spread open cotter pin. Wear gloves if you use a paper clip. It will get hot from the ten amps of current. On my '78 model, the two wires in question are bolted on. They can be connected very easily by placing a screwdriver blade between the two of them.
If jumping the relay that way works, you will know the battery, cables, connections, and starter motor are ok. The problem has to be with the contacts in the starter relay or something in that tiny-current circuit.
Tuesday, August 31st, 2010 AT 3:59 PM