Welded on my XJ...now problems

So I was finishing up my rocker replacement today and had been welding away and needed to move my jeep closer to the welder to tack the (passenger) front fender to the new rocker. Fired it up and it was running great like always. Tacked the fender onto the rocker and then jumped in to move it forward out of the gravel and onto the driveway. To my horror, I turned the key and got nothing but clicks like when your battery is dead.:scared:
Long story short, got the jumper cables out, hooked it up, and it cranked, and cranked, and cranked, but no start.

I got it to start (finally) by pumping the gas pedal while cranking, but it would not stay running if I let off the gas. Got it to start and roughly idle, but it kept wanting to fall on its face. For instance, I was holding it at around 1500 rpm's, and when I let off, it would stumble and die on me. I finally got it to idle on its own, and it will start and run, but it seems to have a miss now and a slightly rough idle.

I have read all kinds of stuff about welding on a vehicle and whether or not it will fry anything. Some say its BS, some swear it will fry your ECU, but it's the only thing that could have done it. There is no way my battery drained that quickly from the time I moved it to the time I was done tacking the fender (10 minutes). The only thing I can think of is that my ground was too far away (right under the B pillar on the rocker), and the current traveled up the fender to the battery ground, which was still hooked up to the battery. I know, I know, my fault.

So my question is:
What do you think I could have fried? I've found a few threads talking about alternators, TPS, ECU, battery, etc, but I'm at a loss. I have a 3 hour trip in a couple days and I don't want to find out what is fried in the middle of the trip. Any help is appreciated! Oh yeah, 99 XJ 4.0 AW4

Symptoms sound like cps

Check all fuses.

mako my day said:

Symptoms sound like cps

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Upon reading more, I agree. What about the (seemingly) dead battery though?

mg614 said:

Check all fuses.

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Forgot to mention, I pulled and checked all fuses. All were good.

Were you by chance listening to the radio or did you have the doors open (dome lights on) while doing this welding? Starting it up to move it then shutting it back off is not enough time to for the battery to recharge what it took to start the jeep. If it was marginal to start the jeep, then you shut it back off right away, its very possible that there just wasn't enough charge to start it again. The not idling sounds like exactly what happens when you run a battery flat (regardless of how it happens) and it loses the idle settings. Takes some driving around to get it to idle smoothly again, and just holding the throttle is not enough.

donthelegend said:

Were you by chance listening to the radio or did you have the doors open (dome lights on) while doing this welding? Starting it up to move it then shutting it back off is not enough time to for the battery to recharge what it took to start the jeep. If it was marginal to start the jeep, then you shut it back off right away, its very possible that there just wasn't enough charge to start it again. The not idling sounds like exactly what happens when you run a battery flat (regardless of how it happens) and it loses the idle settings. Takes some driving around to get it to idle smoothly again, and just holding the throttle is not enough.

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I had both passenger doors open while I was welding the rocker in. No accessories were on. I did take it up and down the road a few times, but didn't want to go too far in case it died on me. The battery is an Optima blue top, I couldn't imagine it would drain that fast, but I suppose it's possible.

Re: Re: Welded on my XJ...now problems

donthelegend said:

Were you by chance listening to the radio or did you have the doors open (dome lights on) while doing this welding? Starting it up to move it then shutting it back off is not enough time to for the battery to recharge what it took to start the jeep. If it was marginal to start the jeep, then you shut it back off right away, its very possible that there just wasn't enough charge to start it again. The not idling sounds like exactly what happens when you run a battery flat (regardless of how it happens) and it loses the idle settings. Takes some driving around to get it to idle smoothly again, and just holding the throttle is not enough.

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This. Disconnect and charge the battery. Reinstall it and all will be well.

I had the same thing happen. Recharged the battery and all was good.

Curious if you were welding with fluxcore or gas? I was using fluxcore which requires the welding leads to be reversed on my MIG. I think this may have contributed to the rapid discharge on the battery since it connects the + side to the ground of the XJ which means it could be sucking the charge out the whole time the ground is connected (not just when you are welding). Not something I want to test but curious if you were doing the same.

As for why your engine was dying, if you were running with a low battery charge, two things are working against you. 1) the alternator is trying to recharge the battery and 2) the alternator is also trying to deliver enough power to feed the ECU, spark plugs and injectors. That is a big load and likely caused the voltage to the engine to sit lower than normal, causing it to stall. When you rev it up, the alternator is pushing out more juice and can overcome this but when it is idling, it may not have had enough umph to do both things.

As I said, I recharged my battery and all is good so I would recommend that you start there.

HTH
Todd

same thing happened to me the other day. the fix was nothing more than tightening the negative lead to the battery.....easiest and last thing i would think of

tjmotter said:

I had the same thing happen. Recharged the battery and all was good.

Curious if you were welding with fluxcore or gas? I was using fluxcore which requires the welding leads to be reversed on my MIG. I think this may have contributed to the rapid discharge on the battery since it connects the + side to the ground of the XJ which means it could be sucking the charge out the whole time the ground is connected (not just when you are welding). Not something I want to test but curious if you were doing the same.

As for why your engine was dying, if you were running with a low battery charge, two things are working against you. 1) the alternator is trying to recharge the battery and 2) the alternator is also trying to deliver enough power to feed the ECU, spark plugs and injectors. That is a big load and likely caused the voltage to the engine to sit lower than normal, causing it to stall. When you rev it up, the alternator is pushing out more juice and can overcome this but when it is idling, it may not have had enough umph to do both things.

As I said, I recharged my battery and all is good so I would recommend that you start there.

HTH
Todd

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I was using flux core. I remember reading something about how the polarity going one way was bad, but I'm fairly new to welding so it didn't make a whole lot of sense at the time. I'll go out for a long drive and let the battery recharge and hopefully it returns to normal. Thanks for everyone's input!

Your alternator is not designed to charge a dead battery. Charge the battery with a charger first.

I had a bad cps once. It would just crank and crank and never turn over.

Had a really dead optima. I could get it started with a jump. If I didn't keep it throttled, it would sputter and die. New battery = problem solved. I think with a really dead batt like some have said it messes up idle and the alternator won't keep it going.

tjmotter said:

I had the same thing happen. Recharged the battery and all was good.

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Me too. On more than one occasion. And it's annoying as hell having to jump your own vehicle in your own garage. :doh:

That's why I finally did something about it last weekend: installed a dome light override switch. Now I can switch off all interior lights and leave the doors open all day long. Works like a champ!

Well it looks like it was the battery, everything is back to normal and running great. Battery seems to be as strong as ever. I'm still curious if it was just my doors being opened or if the welding played a role in the seemingly rapid discharge of the battery. I'll tell you one thing, I will always disconnect the battery before welding from now on just to be on the safe side.

Nice! thanks for the update.

I know for a fact that mine was caused by the welding because I had the doors closed and everything shutdown.

Many people will tell you that they have "welded on thousands of cars and never had an issue with the battery". Others will say "as long as you place the ground close to the welder, the electricity won't travel to the battery". On the first comment, all I can say is that "it depends". If you are welding on an exhaust system for example, you have a lot of rubber isolation which reduces the number of pathways for the electricity and you may not have problems. On the second comment, "afraid not". Even if you have the ground connected 1" away from the work, electricity will travel throughout the vehicle in an inverse relationship to the resistance. While placing the ground very close to the welding point is a good practice and in fact, resistance will be very low between the two points when you do this, resistance is not zero and some current will travel through different routes to get to the lead on your welder.

If you search for "MSD ignition welding" you will find dozens of examples of people who have blown up their aftermarket electronic ignition systems by welding. The OEM stuff is much more robust and forgiving but it can still get damaged by the constant electrical pulses put out by a welder. Some people will say to keep the battery connected because it will act like a filter and protect the electronics. Not a bad idea but as you just found out, best to keep a charger handy.

Like I said, the same thing happened to me two weeks ago and I was welding for less than 5 minutes at the rear of the Jeep.

HTH
Todd