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My friend bought a Jeep (I think a 2000) at a garage sale and he had it running. A year later when we went to get it someone had done something to it: when we connected the battery it's as if the key is turned to start and the starter runs, however there's no key in the switch.

How do I troubleshoot this?

  • Welcome to the site @Rick. I don't understand what you are asking for. Are you trying to get it running, for fix a particular problem? – GdD Jun 7 '18 at 11:26
  • How do we find what's wrong? – Rick Jun 7 '18 at 13:03
  • We can't put the battery in properly because as soon as we connect the second post on the battery the starter engage and turns over and I take it off and it stops. We have no clue where to look. All this without the key in the switch. So weird. – Rick Jun 7 '18 at 13:07
  • @Rick Specifically what jeep? Wrangler? What Engine? – Moab Jun 7 '18 at 15:23
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It sounds like you have an electrical problem or a problem in the ignition switch. When you turn the key to start the ignition switch makes a connection with the starter solenoid or relay which will allow current from the battery to the starter. When the engine is started the ignition switch is returned to on from start and the connection to the solenoid (or relay) is broken, cutting power to the starter motor. The reason it works this way is that the current to the starter is boosted by a coil to high voltage, which would be dangerous to have running through a switch your hand would contact, using a solenoid or relay lets a small voltage control a big voltage.

Here's a diagram of a starter system: Starter system diagram

As for what is going wrong it could one of the following:

  • Faulty ignition switch: maybe someone tampered with it to try and run it without a key, or maybe it is stuck to start. Try twisting it to off if you haven't already. It's also possible it's simply broken and making contact no matter what you do
  • Hotwiring: it's technically feasible to hotwire a car that doesn't have an immobilizer on it, of where the immobilizer has been disabled. An immobilizer is a system which will prevent the car from running unless a specific key or dongle is presented. Bypassing the ignition key mechanism to present power to the starter system
  • Electrical fault: If the right wire gets its insulation worn off and comes in contact with power then the starter will run
  • Solenoid/relay bypass: maybe someone took the switch out of the equation
  • Malfunctioning solenoid or relay: the relay could be stuck closed, allowing power to the starter
  • ID10T error: never dismiss the power of stupidity, someone might have deliberately run electrical connections or messed with something without understanding the possible results

I would start with inspecting the ignition switch for tampering or function. If wires are dangling all over and someone's used wire nuts or just left them bare then it's a good indication. Then I would inspect the starter motor and relay connections. Disconnect the ignition switch connections from the solenoid/relay and then connect the battery again, if the starter still engages then the solenoid/relay has been bypassed or has malfunctioned. If the starter doesn't engage then the relay is working and there's no bypass, so the problem is upstream. Use a multimeter to detect power coming down and work your way back to the ignition switch until you find the culprit.

Here's a good page on ignition systems and wiring.

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    It sounds as though the starter is stuck in the engaged position. Like the solenoid is stuck on "go" and continually allows power to transmit. – Pᴀᴜʟsᴛᴇʀ2 Jun 7 '18 at 21:11
  • It could be @Paulster2, disconnecting the ignition switch connections to it will tell. – GdD Jun 8 '18 at 8:28
  • We have disconnected the plug from the ignition switch and as I connected the cable to the battery the starter turn over. We took the starter off and we took it apart and cleaned it and tried it with buster cable and appears to work fine. I put it back in place and didn't connect the battery cable and the ignition wire to it and when I connected the battery cable to the battery and the fuse bocks the head lights are flashing and the cab buzzer goes of as well. My friend thinks there is a problem with the security system. – Rick Jun 11 '18 at 4:49
  • Tomorrow I will try track where the ignition wire at the starter is getting power from as soon as I connect the battery. Anymore suggestion will be considered. Thanks to you guys with your advise you have put us on the right track. Again thanks! – Rick Jun 11 '18 at 4:53

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