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Jeep Starts on its Own

Just bought a 1996 Jeep Cherokee Sport 4.0 Auto trans. Love it so far and it is helping me learn about auto repair… that said… I think I have an interesting problem…

The other morning my jeep wouldn’t start. Power everything works, lights work, back up lights work. Starter had been sluggish so I had it tested. Tested fine. Hook the starter back up and when I attach battery it turns over and runs constantly.

I removed the ignition wire from the starter solenoid and hooked it back up and the same thing happened. So I deduced the starter solenoid was stuck. Bought a new starter and replaced my old. Old starter was tested at autozone and it worked properly there (didn’t run without ignition).

I just bought the new starter anyway. Hook up battery and same thing happens–starter turns over.

Now I’m here scratching my head. How would just the cable from the battery be able to turn the starter over if it is all good?

starter relay hung?

Well the only way that could happen that I can see is that the main battery lead was reconnected to the wrong side of the solenoid, to the motor side that ties directly to the wire for the motor. If that isn’t the case then check the continuity between the two main solenoid posts using an ohmmeter but don’t remove or wrench on the solenoid posts yet. With the positive battery connection removed from the battery, see if there is connection between the two main starter solenoid posts while no power is connected. The contacts should be open. I have seen where over torqueing the solenoid posts caused the main battery connection to short to ground internally. The head of the stud bolt contacted ground inside the solenoid. Simply repositioning the stud bolt back slightly cleared the short. The design of your starter is different and perhaps the same kind of thing is happening but the short is happening between the two contacts and not to ground as your solenoid uses plastic to hold the studs and is isolated from ground. If the ohmmeter shows there is a low resistance between the two posts then somehow the bolt studs have most likely made connection inside the solenoid. Also check the continuity between the main battery connection of the solenoid and the ignition wire contact of the solenoid. That connection should be open also.

If the starter motor runs when you connect the battery up but the engine isn’t cranking then you must have bypassed the battery side of the solenoid posts when you reconnected the battery cable to it or the solenoid posts are somehow shorted together internally. Perhaps due to the connection studs being over torqued.

The starter relay is more than likely sticking. It’s relatively cheap and very easy to replace.

I bought the relay whileI was buying the starter – except the guy gave me the wrong kind!

I pulled my relay and it looks okay but could itstill be malfunctioning.

Check circuit 86 at the relay and if it is hot with the key off the ignition switch is the fault. If that pin is not hot the relay should correct the problem. To check your relay ohm from pin 30 to pin 87. There should be no continuity.

I believe the relay is somewhat generic. The Borg Warner part # R3177 is a direct replacement and can be cross referenced to any brand.

Would I be able to test the circuit just using a circuit tester? It’s all I have… Had my gf try starting with circuit tester in 85 and 86 and didn’t get a light?

Ignition Switch? … I removed the starter because it had been sounding sluggish… was it just an ignition switch all along…

I should have noted I did not get a click or anything when I tried to start the other day.

About to check fuses (doh) and then replace the ignition switch…

If the ignition switch were the cause there would be current at pin 86 when the problem was occuring.

I have the starter disconnected so I could check the relays with the battery connected. I used just a circuit tester with the clamp on the negative battery terminal and then touched the positive in 85 and 86 as my gf tried to start the car and the thing didn’t light up. What does that mean?

With the key turned to the START position pin 86 in the relay box should have 12v and would light a grounded test light.

Touch the #30 pin on your relay to the battery + post and use the test light to check for current at pins 87a and 87. Post the results.

Ok no current at 87. 87a did light up. Testing 86 now

Nothing on 86 when turned to start… bad ignition switch right?

This doesn’t make sense to me… guy at Autozone said he worked for Jeep for a long time and told me to replace the ignition switch though. So I guess I will try it. But if the starter is turning with just the battery wire connected to it… I don’t understand how the ignition switch is even involved

Maybe if you connect your test light to the relay box female slot for pin 86 and repeatedly turn the key from START then to OFF you might find that on occasion switching to OFF doesn’t result in the light going out. In other words the ignition switch might have the START circuit connection closed(turned on) even when the key is turned to the open position(turned off).

If you have the starter bolted to the engine, with no wires at all hooked up to it, and then attach only the large battery cable and not the smaller “s” terminal the problem is at the starter. Either the solenoid is stuck or the battery cable is being attached to the wrong terminal at the starter.

I am losing track of the situation @asemaster. If the starter operates with only the battery positive cable connected the problem is certainly at the starter.