My '73 W200 has no spark, I have replaced about everything in the igintion system. Now I have noticed that with the key off, and the lead alternator wire disconnected it arcs. I have removed all the tape from the wires and havent found any bad wires all the way back to the firewall.

Look under the dash by the steering column....big white connector with I beleive 7 or 8 wires in it....any one of them cooked???

Check your amp gauge, on ever powerwagon Ive had that has had your problem it was a bad amp gauge. Bolt the red and black wire together should fire right up. Very common problem with older mopars seams more in of a problem with the trucks.

Dan

OE dual (4 terminal) ballast/5 pin ECU I'm assuming? What components have you replaced so far? Take off the yellow solenoid start wire off of the starter relay to disable the starter to elim the noise distraction & not run the batt down then have a helper hold the key to start & you check for fire under the hood, 2 pins on the ECU (5 pin) need to b hot in addition 2 the coil positive pri terminal. If not bulkhead is a pri culprit to check 1st. Take off any/all wires off of the coil neg pri terminal & w a jumper wire w alligator clips jump the coil neg pri terminal (not the wire(s) you removed from it) to ground repeatedly like Morse Code & see if it (large coil center secondary wire (dist end held 1/4" from ground)now sparks & if so all is good ex the ECU (or it's ground) or the dist pickup (or their supporting wiring). Now seperate the pull apart dist 2 wire connector & same thing Morse Code touch the male terminal on the body half of the connector to ground & see if you have spark & if so the dist pickup/gap is bad. All w key held to start. EDIT (re) install the coil neg pri wire(s) b 4 you do the dist pickup test