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Here's a weird one... The other day I had the truck idling with the hood open. I could hear a "snapping" sound, kind of like a spark plug wire shorting to a ground. Couldnt see anything, so waited til dark and started 'er up. Had a blue spark jumping from one pwr steer hose to the other pwr steer hose where the metal in the hoses were close to each other. What is this?
Thats what my first thought was, static electricity. I'm thinking: What now, ground wire to my pwr steer pump? This is a spark that isnt intermittent, but looks like the spark on a shorted plug wire when it jumps to the headers. And it's blue, so it must have some juice to it...
Pull each sparkplug wire off, one at a time from the distributor cap, and see if it quits doing it. Also try to notice if the engine idles rougher after taking each wire off. You may find one that makes it quit sparking, and also does not affect the idle quality. This is the wire you need to concentrate on.
Didnt rev the truck to see if the sparking increased in frequency. This started about the time I installed new 1 wire Ford Alternator. I have also noticed that when I hook battery cable to solenoid with switch off, there is a noticeable spark there. Shouldn't be any, I would think. Will have to start pulling fuses and see if its anything in the fuse block, or maybe ignition. I remember reading a post several mo ago, about someone that had put a 1 wire in their truck and had to install a second solenoid to remedy some hot wire prob. Really dont want to do it that way, but if I cant find this, maybe I will.
12 volts is not going to jump an air gap. It will have to be in the thousands of volts to make air conduct electricity. It's either static, or high voltage from somewhere, and the obvious place to look for high voltage is the ignition system.
When I installed the 1 wire alt, I found a wire off of the old reg that seemed to power everything on the truck, including ignition switch. I'm thinking that possibly one of the wires from the reg wasn't hot all the time, wondering if the coil is still hot, or a leg on the ignition switch that needs to be switched off instead of constant 12 volts. Would the coil have a hot side if the key is off? Also, when I reconnect the battery cable to the hot side of solenoid, I hear a clicking sound, possibly from inside the truck. What would this be? this is a 72 F-100