Start issue

My buddy is having a strange problem with his newly purchased (highly modded) XJ. He took it out wheeling though some pretty deep water this past weekend and drove it back from New Jersey to Virginia and the next morning the battery was dead. He tried jumping it off and as soon as he hooked up the cables, the engine started turning over. Assuming the water had something to do with the problem, I beat on the starter solenoid with no luck. I pulled the starter and had it tested at Autozone and they said it passed. I also pulled the starter relay and swapped it with the AC relay and had the same result. I ran out of time to keep TS'ing at that point.
The only other thing I could think of is the ignition switch, but I didn't think that would be likely since it didn't get wet. Would the starter fail its test if the solenoid was stuck shut?

Any ideas?

2000 model year
4.0L
Auto trans.


Thanks in advance

I'd check for mud in the alternator.

Also make sure that moisture did not get into one of the interior light switches or something of that sort. Door switches are a notorious eater of batteries.

You should do a current drain test, and see if you can find where it's coming from that way. Get an ammeter on the battery terminal, and start pulling and disconnecting things until it drops.

Thanks, I'll give that a try.

check battery for amps and voltage. so first, put a long slow charge on the battery.
get the CCA up to speck and make sure it holds a charge.

make sure there is no corrosion at the terminals or in the lines. makes sure all battery grounds are good and clean.

if after you charge the battery, the thing still wants to die after dirving for a while (maybe 1-2 hours to fully kill the battery if that) then
you probably just killed the alternator in the mud. take it off and get it tested.

check the dizzy for water.

for fun if all of that doesnt fix it, test the TPS and CPS.

I'm still confused as to why it's turning over with the ignition switch off. I played around some more today. We swapped the battery out of a truck and it still turned over with the key off. I also swapped the starter with a new one I had lying around. Still turned over with key off. The only thing that will keep it from turning over when the battery is connected is removing the starter relay. I unhooked all the wires from the ignition switch and then reinstalled the starter relay with the truck battery hooked up and it still began turning over. I told him to get a service manual so I could look at the wiring diagrams.

Finally figured out what the problem was today. I broke out the multimeter to check for for voltage at the ignition switch connector. I was getting about .5 volts from the wire going to the fuse panel with the ignition switch removed. should have been 0. I think this is what was causing the starter relay to energize, making the motor turn over. I pulled off the connector between the ignition switch. Still reading between .5 and 1 volt. Checked voltage at fuse 19 on the passenger's side. It read about the same on one side, and 0 on the other. I then pulled off the connector that is held in with the bolt in the fuse panel and found corrosion and dirt in it. Also pulled off the smaller connector with the wire going to the relay and made sure it wasn't corroded. While I was under there, I realized that I could see light coming through right above the fuse panel where the antenna wire goes into the fender. The rubber grommet had come loose and the tires were throwing water right on top of the fuse panel! After I cleaned the connectors up a bit, I stopped getting the voltage. Tried cranking it after everything was back together and the starter motor was turning, but you could hear the gears touching the torque converter gear, but not engaging. Went and bought a new starter and it works like a charm! Couldn't have figured it out without the FSM. Those things are worth their weight in gold!

Thanks guys !