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No Start After Welding (sort of)

nvrenuf

nvrenuf

Holy crap, it's running!
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Last weekend welded a patch panel over the a/c hole on the firewall. BEFORE welding, I disconnected both battery cables and unplugged the MSD box. After welding I cranked up the truck and moved it to the back yard where I keep it. While moving it it did sputter and tried to cut out a couple of times but I attributed this to my just twisting the battery cables on instead of wrenching them tight (I later found them to be loose).

Today I tried to crank it and it will only spin over but wont actually run. Both the MSD box or fuel pump get power from "ignition" spots in the fuse box but today both spots are dead. All fuses are good.

I also noticed that the battery symbol on the inst cluster is now lit any time the battery is connected regardless of key position.

I don't see where this could be related but could I be wrong? Any ideas as to where to look next? Ignition switch?
 
The only fusible link I found was at the power block on the firewall above the master cylinder and it has 12v on both sides. Where are others?

I did have a small braided ground strap I moved while welding, would a small strap like that stop the show?
 
yes that strap can do all of those things it ties the body sheet metal to the battery ground.
 
welding on the firewall, where was the ground clamp attached?
 
cybrfire said:
welding on the firewall, where was the ground clamp attached?
Click to expand...

I've removed the a/c box so I was welding a patch on the big hole for the evaporator with my ground clamp also on the firewall in the hole for the blower.
 
wish you would have called, was just hanging around the house. can run by tomorrow eavnin.
 
Thanks but I can't do it tomorrow evening, got a wake to go to. Maybe later in the week.
 
nvrenuf said:
I've removed the a/c box so I was welding a patch on the big hole for the evaporator with my ground clamp also on the firewall in the hole for the blower.
Click to expand...

Wow, should have been good to go like that.
 
The thing that really throws me is the little battery lamp that's staying on any time the battery is hooked up (regardless of key position).
 
The lamp might be lit because a diode popped in your altenator (or maybe all 3 in the diode trio)..I suppose its possible for welding current to still get into the altenator with the battery cables dissconnected,but geez,I've welded hundreds of things on trucks and forgot to take the battery cables off,only twice have I had anything "blow" ,my stereo amp fried in my van when I was arc welding patches on the tail pan,and once I popped tail light bulbs when I welded a trailer hitch on a friends truck..I'm a lot more careful on newer trucks with computers!...

Snap-On and other tool makers now have a capacitor type device you clamp across the battery terminals now,no need to take them off before welding using one of those things...

There are two more fuse links in the thick red wires at the starter solenoid,they are bolted to the same terminal the positive battery cable goes on...usually you'll get no power to the cab if they fry..
 
Excellent! Thanks!

Oh, I assume a quick check of the alt diode would be to disco the alt and see if the light goes off? If so, I can take it off and have it checked at VatoZone or where ever.
 
Yup....all sorts of transient voltages and spikes can occur when welding on a vehicle.....alt diodes may have toasted...

Luckily the worst thing I have ever had happen is a steel braided brake hose burst into flames as it acted as the ground strap to the rear axle when I welded on some shock brackets....

the ground clamp was attached to the frame......:whistle::whistle::whistle:
the 90 amps passing thru the hose was a little too much for the braiding on the hose...
 
wasted wages said:
Yup....all sorts of transient voltages and spikes can occur when welding on a vehicle.....alt diodes may have toasted...

Luckily the worst thing I have ever had happen is a steel braided brake hose burst into flames as it acted as the ground strap to the rear axle when I welded on some shock brackets....

the ground clamp was attached to the frame......:whistle::whistle::whistle:
the 90 amps passing thru the hose was a little too much for the braiding on the hose...
Click to expand...

I thought that was a "helpful" friend that did that to your rig Frank?

Electrical can be damaged when welding, but so can many other things. You always have to try to imagine the ground path before you strike the arc, or you could have arcing through diff bearings, or tranny parts, or even the engine internals. Those are expensive mistakes to make...

Rene
 
I thought that was a "helpful" friend that did that to your rig Frank?
Click to expand...

sorry...I was speaking in general terms..we both work on the rig, but I own it...

actually it has happened twice......once when we were building the rig and I went to weld on some tabs for the rear disk brake hose brackets...

and then the last time when we were putting the shock brackets on....my helpful friend did that one...
 
Since I stil have some more welding to do on the cab, any issues with finishing before I fix what I killed? I'd hate to fix the no start problem and then work my killer magic again. :doah:
 
I wonder if grounding the frame of the truck to a water pipe in the garage or a ground rod would make a difference?? :dunno::dunno: couldn't hurt......it would give the transient voltages a path to ground since the truck is on tires.....a jumper cable from the frame to an earth ground should do it...

also I have seen welders in our fab shop wind the stinger lead from the welder around pipes and other things they weld on....they tell me it cuts down on the magnetism effect created by welding ????:dunno::dunno::dunno:..

just throwin that out there for discussion...found this...

http://www.esabna.com/us/en/twi/Arc-Blow.cfm

"If arc blow still persists when using AC for the root run, the power cable can be wrapped around the workpiece several times near to the joint. Care will be needed if preheat is applied."
 
I was always taught to disconnect the battery cables and put the grounding clamp as close as possible to where you are welding to allow a clear path... hasn't failed me yet :thinking:
 
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