To make a long story short, a guy pulled my positive lead off of the battery while my truck was running. It ran for about 5 seconds and then died, never to start again. So here is the deal...

Turns over and everything seems to be working fine other than the fact that it wont start. The battery is new, alternator tested good, replaced voltage regulator, replaced all of the fuses in the interior fuse block.

Its a 1978 F-250 with the 400, 2BBL ford motorcraft carb, manual trans, 4wd. I do believe all of the ignition parts are original unless otherwise stated above.

HELP ME PLEASE! and thank you.
Todd

 

That's odd. I've done that many times and never once had an issue. That being said, I haven't done it on any newer vehicles. Matter of fact, I haven't had to do it in many years. Good Luck.

 

Well seeing that i already replaced just about everything in the ignition system i decided to check out the ignition control module (it was only $25). So I swapped it out.

WIN!!!!!

It fired right up...

Lesson of the day: NEVER UNHOOK THE POSITIVE TERMINAL WHILST VEHICLE IS RUNNING.

I know nobody got a chance to help me, but im sure this thread will help someone in the future.

 

Been there, done that. I got tired of preaching it all the time though. I seemed to always be the doom and gloom guy, "can't do that", should not do that", and everyone keeps doing it with no problems, so I shut up about it.

 

I will have to remember that that next time that I am tempted to do it. Like I said, I haven't done it in years. And even then, not to anything newer with a computer. I would assume the same thing applies to the ground cable.

 

Alright, I'll bite. I haven't done this in a long time and never on a new vehicle. But I remember that doing so used to be a way to test the alternator. How could removing the positive charge from a running system harm the engine.

Not trying to start a flame war...just trying to better educate myself.

 

Removing the battery cable on a running engine will/can send a voltage spike of about 100 Volts through the system. This can fry anything that has transistors or IC's in them. In this case the Ignition module was fried.
In computer trucks it can also take out the computer and anything else that is on like the Radio.

The battery is the filter capacitor and a load for the alternator to keep the voltage spikes from happening.

 

Thanks. I will make sure to remember this for any future work I do on my engine.

 

In my case, the truck was having charging problems, I took the battery + wire off the battery, it ran like his for about 5 seconds and quit. Same thing, the ignition module was burnt out. After some investigating, it turns out the regulator had shorted and the alternator was basically wide open. The only thing holding the voltage down to a reasonable level was the battery. As soon as I took the battery cable, the voltage went sky high and blew the ignition module. If I would have had the radio playing, I am sure it would have burnt it out also.

 

Do you think there is an exception for vehicles with 2 12-v batteries hooked up in parallel - such as in many if not all diesels?
I did this very thing once to help out a cousin with a dead battery - I had no jumper cables. I figured that once I had my diesel running, simply to remove one of the 2 batteries to transplant temporarily into her car couldn't hurt anything. I was careful not to short out any cables in the process.
I had my diesel running at the time since I couldn't be sure it would start on a single battery.

 

There were ignition control modules in 1978?

 

There sure is. Cheap, small, and a total of about 6 wires... Very simple piece really.

Ignition Control Module by BWD - part# CBE7Z

 

I tell people not to do this all the time, but they keep doing it. Maybe this thread will help people understand.

Even when the engine is OFF, you should not remove the positive cable unless the negative cable has been removed first. Again, people do not listen.

 

Is there a reason other than the safety aspect of not shorting the wrench on a ground when loosening the positive clamp?

 

That is the only reason, but it's a good enough one by itself. Put in the category of looking both ways before crossing the street or pulling out into traffic.