Spark problem from hell

I have a 91 bronco 351w efi. I have been having this problem where my engine will just shut off. I checked my fuel, and have plenty of pressure at the injector rail. Then I checked for spark, and bingo no spark.
It is an intermiting problem. It runs great for a few days, then all of a sudden it just shuts off, like I turned the key off. No chug, no sputter.
So far, I have replaces the coil, distrubitor (complete), TFI, EEC,Fuel pump relay, alternator, new leads on the battery, TPS, plugs, wires, rotor, and cap.

After each piece was replaced, I would get it to start, and run for a few days, then it would act up again.
The last thing I am looking at if the ignition suppression resistor.
When I turn the key on, I get @12v comming out of the coil, when I crank the engine, it drops to @6v. Was told it could be the resistor.
Before I tear appart the wireing on the engine to find it, I was hopeing for some advice.

[bc backroads]

the voltage should drop to 6-9 volts after the engine is running, that is normal , you might want to check your grounds on the frame and block, it could also be the ignition itself, i have experienced the same thing in the past, it was caused by a keyring with too many keys on it bouncing up and down when wheeling, it doesn`t seem like a lot of weight, but factor in all the bouncing around , and it wears the switch out

[JWharden]

Yeah That my money is on the ignition switch. and double check your grounds esp near battery.

[Jeep Fever]

Is a push button bypass out of the question??? Cheap and easy fix if it isn't... no test and quick to do.

[JWharden]

Not really if the switch is fact bad, you could burn your truck to the ground.

Check these links. Ford Ignition Switch Fires and http://www.flamingfords.info/affohome.htm.

I talking about the electrical part, not the key cylinder. The switch is midway down on top of column.

At this point, I replaced the comp.
I have also gone through all the grounds and made sure they where good.
The ignition is a mechanical ignition with a remote switch. I didn't think it was an issue since if the ignition was bad, I figured I wouldn't get power to the relays, and starter. But I tried wiggling the wires around while trying to start it, and nothing happened.
When The problem happenes, I get everything i.e. starter, injection pulse, fuel pump, wipers, lights, horn, radio, locks, windows, and everything else I don't feel like typing. The only thing I do not get is spark.
I have made a discovery though. I noticed that after draining my battery trying to start the truck, I hook up jumpers to it and it tends to fire up.
I have new battery leads, solonoid, and checked all connections, so I am at a loss for that one.

[bc backroads]

well it sounds like you have covered all the bases, all that is left is trying another coil or disributer, yah its not the ign switch if all the other accs work, i am at a total loss, good luck

Don't feel bad, thats what every mechanic, and Ford guy I know has said.

try finding some one who has a snap on scanner and pull the cods if no codes do a wiggle test and try to make it quit running while running the test 2 see if it picks up any thing is this an auto or standard shift truck

It is an automatic. The truck died on me the other day again, and I managed to get it running enough to get back home. Once I was here, I tried wiggling every wire and connection I could find, ( in the engine area, and under the dash) to see if I could get it to stall again. Try as I might, I could not get it to die.
The check engine light hasn't come on since the last code check I did. That test came up with a bad distributor and the sensor that tells the engine how much fuel is going out the exaust. ( can't remember the name of it).
I changed the distributor and the sensor. ( I changed the electrical part of the sensor, not the physical part that goes down to the exaust).
I plan on spending the entire day tomorrow going through the electrical system.
I had rebuilt the lower half of the engine last summer, and maybe I didn't put something back where it belonged. This is the only thing I can think of at this point. If this doesn't work, I am going to have to send it in to the shop and have them try to find the problem. I can't take this much longer.