Here's the thing. MOST modern ECUs are "4 pin." You can NOT tell by looking, because some boxes have 5 pins, the 5th is a dummy, so you can only tell by using an ohm-meter to check for continuity.
SO if you somehow got the resistor in wrong, you will have the wrong resistance hooked to the box, whether it's a 4 or 5 pin box
Study these diagrams, which show the difference between a 4 and 5 pin ECU
You CAN use a 4 pin ECU on a PROPERLY WIRED 4 pin resistor, it's simply that the "other side" of the resistor is not hooked to anything, and of course a 4 pin box will ALSO work with the proper 2 terminal resistor
The diagrams below do NOT show the ballast bypass/ start circuit, which is simply one brown wire, comes from the ign switch, to the coil + side of the ballast. That brown is HOT in start and feeds good hot battery voltage to the coil during start
You need to run two tests,
1 To make sure you have good voltage to the system for start, hook one probe of your meter to coil+ and the other to battery +. Crank the engine using the KEY, NOT by jumpering the start relay, and read the voltage. You are looking for a very LOW voltage, the lower the better. Anything approaching .3-.5 V (three tenths or 1/2 a volt) means you have too much voltage drop in that circuit
2. Hook one meter lead to the "key" side of the ballast, your other lead to battery + Turn the key to "run", engine off. Again, you are looking for a low voltage. Anything over .2--.3V (three tenths) of a volt means you have voltage drop in the ignition harness
Your top suspects for trouble are the bulkhead connector, the connector on the ignition switch, the switch itself, or problems in the ammeter circuit.
For test no2, your circuit path is battery -- fuse link -- bulkhead connector -- ignition switch connector -- through the switch -- back out the switch connector -- back out the bulkhead -- (on the dark blue "ignition run") -- to the igntion system.
This "ign run" (also referred to as IGN1) is UN fused and supplies ignition, alternator field, regulator "I" terminal, electric choke if used, and on "smoggers" possibly a couple other things
The "brown" bypass circuit, also called "IGN2" is one wire, comes right off the ign switch, through the bulkhead, and to the coil + side fo the ballast
These came from "MyMopar"
http://www.mymopar.com/index.php?pid=31
4 pin resistor, either 4 or 5 pin box
LOOK CAREFULLY at the drawing of the 4 pin resistor. See the "upside down U" at the bottom? This is important, and establishes correct wiring for the resistor. If you turned that resistor end for end, the resistances in the circuit would be wrong, as each "side" is different resistance
2 pin resistor, 4 pin box ONLY
A 5 pin ECU MUST use a 4 pin resistor
