troubleshooting for spark

[GN]

I am getting no spark out of my coil. I checked the coil and replaced with a known good one and still no spark. How do I start the troubleshooting process? Can I run a temporary jumper from the battery to the + terminal on the coil? Do I need to remove the brown wire and blue wire before I do this? (the motor is a stock 318 71 build date) Will that give me power to start the motor? When I check the wires, does the car need to be cranking or the key in the run position?(troubleshooting process on the wires) Thanks for any help. The engine does crank.

[TylerCharger69]

Electronic control module?

[A383Wing]

Do you have 12v to the "+" side of the coil with the key on?  Do you have 12v at the "-" side of coil when key is on?

Do you have 12v at the coil when the key is in "start"?

(I don't mean a test light, use an actual multimeter set on 20v scale, black lead to ground, red lead of meter to the above test points)

Need these questions answered before further diagnosis is made

[Nacho-RT74]

Can I run a temporary jumper from the battery to the + terminal on the coil?

Yes

Do I need to remove the brown wire and blue wire before I do this?

No, and in fact don't do it, because if you try to start on jumping the starter relay, with ballast unplugged will be cutting the power to ECU when cranking if key not in RUN. You can unplug ballast and keep the key in RUN though.

if 5 pins module with dual ballast, simply don't unplug because 5th pin won't get power on any way

Will that give me power to start the motor?

No, just key on START OR jumping relay will power the starter motor

When I check the wires, does the car need to be cranking or the key in the run position?

if you jump the coil directly from batt you can start up the car from interior as regulary without problem, just that to cut off the power when truning off by key won't cut the power and Jumper to coil will keep the engine running

if you feed the coil directly from batt, doesn't care the ign switch position, because even OFF you will be feeding the ECU through ballast and of course the coil. In fact you can jump the starter relay with key in OFF and will start up.

feeding the coil you will be bypassing ign switch and wires up to ballast. If engine starts up, then some on that area is damaged HOWEVER ballast will be still working somehow, because through it ECU will keep feeded.

If engine stil doesn't start you can get broken ballast, ECU or dist pick up coil ( or related wires/plugs ). Also bad ground at ECU.

To discard ballast you can also jump both sides of it.

[GN]

It was the ballast resistor. When I took it off it was warm, replaced it and she fired right up. I thought the BR was bypassed when cranking? What would cause it to go bad? Should I be looking for something else to prevent this from happening again? THANKS ALL FOR THE HELP!