Hello all , new here

I have a 02 dakota and it was doing some welding to the bedside the other day without disconnecting the battery ... yes i know but never had any problems before with any of my rust buckets (using flux core mig and ground clamp never touched the truck as i was welding a hook on and i put the clamp on the hook, butted it against bed a put a few tacks down. i then pulled the dent out the bedside using a ratchet strap lol) anyway i then started it up just fine and moved it a few feet forward and shut it off for the night.
next day i try and start her up and i get crank but no start. i then just work on the body work ( no more welding) and i leave the battery off over night.
The next day i call my friend over to help fix the issue , i connect the battery and ... she starts but struggled a bit to get going but was fine after that. That night i leave the battery connected.
next day i come out and try to start her. i get crank and no go like i originally did so i leave the battery off over night just to be sure that it does fix it and wasnt just a fluke.
next day i hook it up and she starts way better than the day before. Also i can hear the pump every time i start so its not that, fuses all look fine , havent done a spark test.

now idk what ive ****ed while welding to it but it seems that unhooking the battery will make it run the next day. im in the UK and getting parts aint easy but my first thought was ecu as im assuming there's nothing in passenger bedside which controls anything like that which i might have buggered up. other than that i have no ideas. from now on them bloody battery's will be disconnected even if i cant be arsed.

thanks for taking the time to read my silly mistake. god bless

 

Any codes? Have you tried connecting a scan tool to see if the ECU is communicating? You could have sent some serious voltage up the grounds into the computers and sensors. If a scan tool can connect and properly interact with the computer, start looking at all of the grounds. Verify continuity on the wires and then move to sensors. This easily could be more expensive than you want to work with. Edit: Also try a different battery.

 

yes i hooked up a 2 scan tools to be sure and there's only 1 code which was there before which is evap system. nothing else there.

 

i just find it weird how i disconnect it over night and it works like it resets the computer and has a fresh start. i was thinking grounds at first but surly if it was a ground then it wouldn't work at all right ? rather than it working when i take the battery off over night. also when it does run and i shut it off , i can start it back up straight away just fine almost like there's a memory module which cant hold data for long on how to start the truck or something like that?

 

Fried computers can do all sorts of wacky nonsense and are pretty hard to completely diagnose. A ground can be good when cold but fail after it warms up slightly. Honestly I'm leaning towards a computer but just to be safe check the grounds and visible wires for damage. Did you try a different battery? Get it tested if you don't have one you can swap in.

 

I'll try a different battery in a few days and check the all grounds soon once it stops raining and update. thanks for the help. if anyone is reading this and has different ideas please have your say.

 

So once it's running, it runs fine, but only one start? Does it re-start hot?

 

yes once running i can turn off and back on just fine. its just if i leave it for a length of time i doesn't want to restart

 

I've had ground issues due to this exact same reason before, luckily those vehicles didn't have ECM/PCM electronics or I'd have likely gone down this same road already. I still learned my lesson and now unhook my battery ground before ANY welding.
I'd start by checking all of your grounds. I'm sure there are diagrams available to show locations, but I'm also new to Dakota's so I haven't got that far in to my collection of manuals for mine yet. Also not sure if fusible links exist on these trucks, but I've popped a number of those from welding over the years. Most likely a body ground if that's the issue, so I'd start under the hood and trace any grounds from the ECM harness, and anything else related to ignition, crank sensor, etc. Outside of grounds, symptoms lead me to believe ECM or even a sensor. Try the reset again, you can expedite the process by unhooking battery ground and depressing the brake pedal for 15 seconds or so. Reconnect batt, start it and ensure all of your sensors are reading out with a live data scan tool. I'd say it's in the realm of possibility that if it's not a ground or the ECM that's the problem, that a sensor is not reading, or damaged and sending false data that the ECM is storing, making it fail to start after the data is stored and restart is attempted. I'm not sure what the sensors should ohm out to, but I'd maybe try checking that your sensors are good as well. (o2, crank position, etc)

Anyone feel free to correct me here and I won't be offended. I'm only giving info based on my past experiences with other vehicles and what worked for me.
Either way, best of luck, electrical issues are a bugger, and it's often the simple things that get overlooked.

 

thanks buddy, i'll give everything a shot when I get the chance.