Was going over to a friends house to pick up parts in my truck(73 D200). Suddenly it just died.

I can crank it over and when I let the key off it dies.

I was able to baby it back home by starting it and holding the key in one position while I drove. No gauges worked all the while, except my Amp gauge read "charge"

Is this the Ballast Resistor causing the issue or is it the ignition switch itself?

What else could it be?

Resistor, or wiring issues, possibly at ecu or bulkhead. Most likely not ign switch.

Well I have replaced the resitor with a known good one.

I can turn the engine over with the key and it starts,the second I let go of the key it dies. If I hold the key in one "sweet spot" it runs just fine.

Check the bulkhead connection.

I'd take off the starter solenoid wire to termporarily disable the starter (to keep from running the batt down and for the noise distraction) and have a helper hold the key to "start" while you check voltages to the ballast, to the ecu, to the coil positive primary terminal all of which need fire. Start at the bulkhead and work downstream or if your good there go back toward the ign sw. www.mymopar.com should (dont know if they have truck apps) have the colors to help you. (temporarily) disabling the starter will skew your readings as it is not now a normal cranking voltage reading(s) but you have an outright "open" somewhere that'll be apparent when you test that particular connection. Is this an OE 4 terminal ballast/5 pin ECU? If so 2 pins on the 5 pin ECU need fire. Grab your VOM

Well ill call it a "ghost in the machine" I went back out and tried to get it to fire,and let my hand off the key and the truck stays running,all the gauges come alive..Like normal.

Of course its itermittent(sp?) and will only rear its ugly head in the worst possible times.

For now,im gonna just drive it and see if it does it again,ill make sure I note what occurs when this condition happens,and I will make sure I refer back to this post (if and) when it starts acting up again.

Thanks for the advice.

I think its the ballast resistor, some mopars when you turn the ignition to start bypasses the resistor to allow full voltage to the ignition since the starter pulls so many amps, as soon as the motor starts and you release the key the voltage is supplied through the resistor which also supplies reduced voltage to the gauges. Pretty easy to check, make a jumper wire to jump the resistor start the truck, if it keeps running fine, but if it happens again, us the jumper to bypass the resisitor if that works you know your problem. WARNING dont run it for long with the jumper as its pounding the voltage limiter on your gauges and could cause some damage.

intermittant pickup failure is very common also.

I have diaged this in the past, but having a spare electronic distributor handy.

When it quits. Verify you have no spark, by pyulling the coil wire and obsrving for spark whle turning the engine over.

If no spark is present, plug in the spare distributor (at the 2 pin magnetic pickup lead) and spin it by hand while looking for spark at the disconnected coil wire. If you suddenly have spark, you found the problem.

My car did this once and I thought it was the connection at the bulkhead. Turns out when I let go of the key at the gas station it just didnt snap back to the right spot. Headlights worked, interior lights work, hazards work, anything that works with the key off works.

Had a bad pickup coil do that...ensure the replacement resistor is good also