Welding on a working vehicle

[fotoflojoe]

In all the welding threads here, I've not seen this topic covered, and I'm a little curious.

When welding on a working vehicle - not a disassembled project, but one that runs and drives - what precautions should be taken? Specifically, with respect to things like electrical systems, fuel lines, fuel tanks, interiors, etc.?

For vehicles with engine management systems, is there a danger of frying computers with current? Should batteries and electronics be removed?

How would you weld near a gas tank? Or, would that just be insane?

Thanks!

 

[akdiesel]

I have heard on the newer vehicles you need to disconnect the batteries and remove the computer all together.
The older vehicles you just disconnected the battery and connect a chain to the frame and drop it to the ground.
As for the tank. That is just a wise thing to not weld next to a potential vapor hazard. Full is less dangerous but still not advised.
Keep in mind also the engine bay as well as any place that may have oil drips or even grease.
You could pick up a fire blanket at the weld shops and drape it over anything that you want to protect. And keep an extinguisher next to you.

 

[bugdust]

The newest vehicle I've welded on was probably a mid 90s MR2. I've welded on quite a few vehicles though...mostly bodywork or exhaust systems. I've just disconnected the battery. I've never heard of any problems from the owners.

Most newer fuel tanks are plastic. Common sense should tell you not to weld near a fuel tank without proper precautions. Buy a weld blanket or two and a good fire extinguisher.

 

[jdcompman]

One thing many people don't think about is the undercoating on cars. If you are welding anywhere near that stuff be very careful. Once that undercoating starts to burn, it smolders for a very long time and I have heard of many cars that go up in flames hours after the person was done welding on it. Just make absolutely sure that this stuff isn't smoldering or even a hint of warmth before you leave the project for the day.

 

[MXtras]

I have seen this topic come up several times over the years. The general consensus is to keep your "work clamp" close to the weld site to avoid the possibility of the current trying to find an alternate path through the computer.

Personally I disconnect the battery just to be safe.

Shield the fuel lines, filler hoses and such from sparks and excessive heat and if you are close to the tank, have a second person around to keep an eye on things while you are welding. The intense light from the arc is enough melt plastic so be cautious.

Scott

 

[nismomans13]

I have seen this topic come up several times over the years. The general consensus is to keep your "work clamp" close to the weld site to avoid the possibility of the current trying to find an alternate path through the computer.

Personally I disconnect the battery just to be safe.

Shield the fuel lines, filler hoses and such from sparks and excessive heat and if you are close to the tank, have a second person around to keep an eye on things while you are welding. The intense light from the arc is enough melt plastic so be cautious.

Scott

this man speaks the truth. My work clamp is always as close to my weld area as possible. If i'm going near the gas tank, it either comes out, or a welding blanket covers everything.

Common sense is the best tool to have in the shop, and its irreplaceable. Sorry, but Snap On doesn't sell it either.

 

[Fab-Worx]

I have seen this topic come up several times over the years. The general consensus is to keep your "work clamp" close to the weld site to avoid the possibility of the current trying to find an alternate path through the computer.

Personally I disconnect the battery just to be safe.

Shield the fuel lines, filler hoses and such from sparks and excessive heat and if you are close to the tank, have a second person around to keep an eye on things while you are welding. The intense light from the arc is enough melt plastic so be cautious.

Scott

this is good advice. keep your clamp close and your surface that your clamped to clean. disconnect the battery. make sure fuel, brake, and electrical is out of the way. I always work with a full tank of gas.. although still dangerous a full tank is safer then an empty tank. I also put a welding blanket over the tank and filler and frequently use air to blow out any fumes that might build up under the blanket.

2 more things to note: clamp your ground to what your welding ie frame, axle housing, control arms etc. I have seen bad grounds cause arcs that melted brake lines etc.

Also remember your air bag will hold memory for some time after the battery is disconnected. Be especially carefull around airbag wireing and sensors. it doesn't take much to set them off. the current feedback caused by a bad ground or a shorted (melted) wire or even the H.F. from a plasma cutter can be enough to set them off.

So just make sure your grounds are good and important stuff is out of the way.

 

[BigE]

I work for a company that upfits work trucks. Our practice is to fully disconnect the battery (positive and negative leads) before welding and to ground close to the working area. Of all the chassis we deal with, one manufacturer has had issues "frying" the instrument cluster even if the battery is disconnected. However, this usually happens when the welder forgets to move his ground when he moves to weld another area.

 

[Stick]

In my job, we weld on everything from firetrucks, to police cars, to high dollar heavy equipment and trucks. Standard practice in our shop is to place the work clamp like an adult (close to what you are working on), and use of an antizap (or a couple of them, depending on how the batteries are set up. No disconnecting of batteries, removal of ECM's or the like, which would be a nightmare in a firetruck or police car.

We have fried a couple of instrument clusters welding the "standard" way (unhooking batteries, etc), but since switching to the use of an antizap, we've have yet to have a problem.

 

[akdiesel]

In my job, we weld on everything from firetrucks, to police cars, to high dollar heavy equipment and trucks. Standard practice in our shop is to place the work clamp like an adult (close to what you are working on), and use of an antizap (or a couple of them, depending on how the batteries are set up. No disconnecting of batteries, removal of ECM's or the like, which would be a nightmare in a firetruck or police car.

We have fried a couple of instrument clusters welding the "standard" way (unhooking batteries, etc), but since switching to the use of an antizap, we've have yet to have a problem.

I had no idea they had somthing for this type of work.
What exactly is an antizap, how does it work, is it affordable for a hobbiest, and where do purchase one?

 

[malibu101]

X2 on the antizap. ????
I have been around alot of different welding processes, while not being a weldor by trade I have never heard of this term before either.
Please enlighten us.

 

[Racer_X]

I've never heard of it before, either. Google found it for me right away, though:

http://www.ntxtools.com/network-tool-warehouse/OTC-3386.html

 

[W-Cummins]

The intense light from the arc is enough melt plastic so be cautious.

Scott

Now there is a good one!


William...

 

[Skyline]

Back when I was in college, a buddy of mine bottomed out his BMW 2002, and scraped a hole in the gas tank. Since the tank was a relative fortune for a college student, we looked for someone to weld the hole up. Sure enough, we found a shop that did nothing but weld car gas tanks. $75 later and the hole was patched. I could not believe what I saw at that shop. They would dump any remaining gas, rinse the inside with water, then blow out anything left as best they could with compressed air. Before welding, they would stick the torch in the hole just to blow out any fumes left...it would make a low level explosion, but nothing serious. They got quite a kick out of the fact that it scared the piss out of us. We told them to call us when the tank was ready...we could not wait for it. These people were nuts.

About two years later, we heard on the news the place blew up. We went over the next day, and there was absoulutely nothing left. I don't remember hearing if anyone died...but my guess would have been yes.

Locally we have had two gas stations burn to the ground in recent years, and both were due to mechanics just attempting to remove gas tanks...not even welding. So should you choose to get the tank out, be very careful with that, too.

 

[bugdust]

Back when I was in college, a buddy of mine bottomed out his BMW 2002, and scraped a hole in the gas tank. Since the tank was a relative fortune for a college student, we looked for someone to weld the hole up. Sure enough, we found a shop that did nothing but weld car gas tanks. $75 later and the hole was patched. I could not believe what I saw at that shop. They would dump any remaining gas, rinse the inside with water, then blow out anything left as best they could with compressed air. Before welding, they would stick the torch in the hole just to blow out any fumes left...it would make a low level explosion, but nothing serious. They got quite a kick out of the fact that it scared the piss out of us. We told them to call us when the tank was ready...we could not wait for it. These people were nuts.

About two years later, we heard on the news the place blew up. We went over the next day, and there was absoulutely nothing left. I don't remember hearing if anyone died...but my guess would have been yes.

Locally we have had two gas stations burn to the ground in recent years, and both were due to mechanics just attempting to remove gas tanks...not even welding. So should you choose to get the tank out, be very careful with that, too.

I could see if they hooked an exhaust hose up to the tank. The gas vapors have to be displaced. DO NOT WELD A GAS TANK IF YOU DO NOT KNOW WHAT YOU ARE DOING!!

 

[Fab-Worx]

I have repaired a quite a few tanks but i take extreme steps to prepare the tank before i will put any flame near it.

a few years back a local guy was welding a tank and it blew up he lived long enough to run out of his buiding and burn to death in his parking lot.

You can never be to cautious when welding a tank.

 

[Skyline]

I could see if they hooked an exhaust hose up to the tank. The gas vapors have to be displaced. DO NOT WELD A GAS TANK IF YOU DO NOT KNOW WHAT YOU ARE DOING!!

No Sh**! Well, at least in theory, a business that does nothing but weld gas tanks should know what they are doing. But if even this place could blow up, it just gives an idea of the havoc that vaporized gas can cause.

On the other hand, I have been a volunteer firefighter for nearly 20 years, and have dealt with many, many burning cars. I have never seen one explode the way they do in the movies. As firefighters, we are almost more concerned about exploding bumper shocks (creates a projectile out of the bumper), than the gas tanks.

 

[dwilliams35]

Now there is a good one!


William...

I don't think he really meant to say "light" instead of heat on that one, but interestingly enough, I have seen some non-UV resistant plastic get degraded and brittle after being exposed to no light other than a welding arc for a time...

 

[Jared]

i have used an anti zap before and it worked great you can pick em up for under one hundred dollars.