Technical Methodical methods for troubleshooting electrical systems

What happens when you disconnect the computer power feed wire?

 

are you using the ECM and the BCM or just only the ECM ??? if your using the BCm ( body control module ) it can be staying on ( they have a tendency to fail ) as for the ECM . they will use some juice while sitting ( memory for fueling ) ( and will spark when hooked up if it sat more than 5 minutes disconnected ) , and you must use the proper rated alternator and battery size as the system uses lots of power and a too small of a alternator and battery will not keep up , and another thing is if the battery is old they will drain quickly ( my truck does this from sitting a month without starting until I replace the battery with a new one then it will hold for 2-3 months without running then go low )

 

He just has the ECM. It has the original alternator that came on the setup. The truck had 17K miles on it before it went through the house. The battery is new and plenty big.

Squirrel, he was going to disconnect it and see what happens. I'll call him today.

 

If you had mentioned in your first post that "OT engine setup" includes a computer, we could have saved a few days of headscratching

 

I figured it would get locked. Trying to abide by the rules, but also trying to help Dad out.

 

roothawg , if your using the OEm alternator , take a screwdriver with the engine off and place it near the rear bearing nub of the alternator , if it pulls ( the field is energizing ) , disconnect all the wiring to it and see if the draw stops , I have run into several of these that the diodes leak and turns it back on as its basically a one wire style ( brown lead switches on/off regulator and should be 0 V with Key OFF ) and when tested by the autoparts store they say they are OK but are not as they charge .
and also check your charging voltage ( should be 14+ for 20 minutes after a start) , if its low ( < 13.5 check the belt tensioner as the serp belt will loosen up if the tensioner ( which are known to go bad on these ) and allow it to slip without a squeal sound , and the last thing I can think of is double check the ignition switch to make sure its not crossing contacts ( not adjusted right ) and keeping something on .