Disconnect EFI?

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Hi, new to the forum but I have gotten a few questions answered by lurking here in the past. I have been welding for a small shipyard for the last five years and am going out on my own now. One of my upcoming projects is replacing the tie down tracks and rails on the bed of the local lumber yard's boom truck and I am wondering if I need to disconnect the batteries and/or the EFI or "the brain" on the diesel engine on the truck before welding. The engineers a the shipyard were always very insistent that we disconnect everything on the boats(mostly Cat diesels) before doing any welding. I will be stick welding with 7018 mostly, a little 6011 where it is crappy.Thanks!
Reply:Yes to be safe disconnect the batteries, and keep your ground clamp as close as possible to the weld zone.Don’t pay any attention to meI’m just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:Anything electricaly sensitive I disconnect the negative terminal and ground it to the positive terminal. Vice Grips are your friend.Miller Big 40GMiller HF-251 D High FreqVictor OA Lincoln 135 MigMK 3A CobramaticBridgeport J HeadCronatron OxylanceRadnor ACAG TorchWeldcraft TIG Torches1 blown knee and two 5 Gallon pails away from being a hero.
Reply:ground it to the positive terminal? Sorry, I guess I don't understand. I get the ground clamp in the weld zone, it will be easy to ground on the truck bed where I am working.
Reply:I disconnect the negative battery terminal and vice grip it to the positive terminal. Then ground the component to weld. Do not attach the welder's ground clamp to the battery terminals lolMiller Big 40GMiller HF-251 D High FreqVictor OA Lincoln 135 MigMK 3A CobramaticBridgeport J HeadCronatron OxylanceRadnor ACAG TorchWeldcraft TIG Torches1 blown knee and two 5 Gallon pails away from being a hero.
Reply:yeah, i didn't think that made any sense. Thanks!
Reply:There are two basic risks:The welding current going through wiring instead of just through the metal you're working on. Easily managable, put the ground clamp near the weld on the part to be welded, so there are no alternate routes through the wiring for the current to take. The magnetic field caused by the welding current acts as a transformer on electrical wires, and create a potentially harmful voltage in the cars electrical system - in very basic words, the wires act as antennas that lead electricity to whatever is connected. Electronics are relatively sensitive, the only way to absolutely protect them is to unplug them from the wiring harness. A more basic approach is to keep any weld current as far away from the wiring as possible, i.e. keep the welder cables well away from the wiring on the car, and do not bring 20' of unnessesary coiled up ground cable up on the truck bed or something like that. With that said, there are countless cars out there that have been welded without any precautions at all without ill effect, so the risk isn't very big (unless you do something really stupid). If easily accessible I'd pull the plug out of the EFI "brain" and any other electronic boxes, if not I'd probably just leave it all in place as long as all welding is done well away from the wiring (possibly by moving the wiring if that's easier).
Reply:Best to pull the negative cable(s) and go to it -- then you're covered.  With that understood, there are a lot of us who have welders mounted on our trucks and who use the back bumpers as welding tables all the time, never unhooking our batteries.  The key, as mentioned before, is to actively control the path to ground.
Reply:Originally Posted by tbone550Best to pull the negative cable(s) and go to it -- then you're covered.
Reply:Originally Posted by G-sonActually, that may not help at all - it may even make it worse! As I said before, the magnetic field induces a voltage in the nearby wires (look up how a transformer works if you wonder). Without the battery there's nothing to "absorb" the voltage, so it may rise quite high. With a battery, it acts as a buffer, a high voltage in the positive leades will be kept down because it basically charges the battery.
Reply:Originally Posted by G-sonActually, that may not help at all - it may even make it worse! As I said before, the magnetic field induces a voltage in the nearby wires (look up how a transformer works if you wonder). Without the battery there's nothing to "absorb" the voltage, so it may rise quite high. With a battery, it acts as a buffer, a high voltage in the positive leades will be kept down because it basically charges the battery.
Reply:tbone550: Interesting.  Originally Posted by ironmangqThe field has to be moving to induce a voltage in other wiring, thats why generators spin. A DC current will induce a magnetic field but unless it is moving over the wiring it won't induce a voltage. AC welding could induce a current in nearby wiring.
Reply:Thanks for the answers guys! I knew I would be glad I finally joined the forum.
Reply:Doing the job today and it is coming along nicely. Thought i would post apicture but haven't figured that out yet.  Disconnected all the grounds and ran myleads on the ground instead of across the bed. Thanks again for the good feedback!