I need some help/ suggestions. I was working on my TJ and dropped a tool that momentarily hit the battery lead going to the alternator and shorted to ground. I didn't think anything about it because the battery lead goes directly to the positive terminal of the battery, so a short doesn't go through any other cirucuitry (or so I think, anyway). However, when I went to start the TJ, it was completely dead. Nothing. I checked the fuses and swapped relays in the main fuse box, but could find nothing. On a hunch, I disconnected the battery ground lead and touched it to the terminal, and got no spark, which I do not understand. I waited a few seconds and tried again, and this time a got a spark, so something (what?) reset itself. So, I reconnected the battery and, now, I have full power to the instrument panel, but the motor still will not crank. I have a code reader, and it does not show any error codes. I don't know what to look at next.
Battery short then no power
- Thread starter JerryK
- Start date
Some things to check:
Make sure your battery is fully charged. Sometimes a short can drain the battery, and if the battery is weak, you might not have enough power to crank the engine.
Look at both the positive and negative battery cables for any signs of damage, corrosion, or loose connections. A poor connection can prevent the engine from starting.
The starter may be the issue. You can do a bench test on the starter or try bypassing the ignition switch by connecting a jumper directly to the starter terminal from the battery to see if it turns over.
Make sure your transmission is in 'Park' or 'Neutral' to see if the neutral safety switch is preventing the engine from cranking.
Double-check the ignition relay and the ignition switch. Even if there are no codes, it could still be a wiring issue in that circuit.
If you have access to a multimeter, you can check for power at the starter solenoid and other key points in the ignition system to see where the power drop-off might be occurring.
You mentioned you got a spark when reconnecting the battery after a few seconds. This could indicate some form of reset, but you might want to try disconnecting the battery for a longer period to reset the PCM completely (around 15 minutes or so).
Inspect all ground connections to ensure they are clean and tight. Sometimes grounding issues can be a hidden culprit in electrical problems.
Thanks for the suggestion. I did not know the alternator wire had a fusible link, but I checked it and it's OK.
Update: I fixed it. It turned out to be the starter motor relay. That explains the symptoms, i.e., power to the dashboard but no crank, but I do not understand how shorting out the battery lead to the alternator took out the starter motor relay. However, the important thing is that it is fixed so I don't have to ride my motorcycle in 105-degree heat in Las Vegas to get around. Nor do I have to have the Jeep towed to a repair shop. Thanks for the suggestions.
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