ecu or coil--how to tell?

[red79]

Hey guys, out driving around a few days ago and the engine just quit on me. Haven't been able to start it since. Been having carb problems, idle circuit was all messed up, so I figured the engine was flooding. Pulled a plug and it was soaking wet, so it seemed a straightforward problem.

Just got a rebuilt carb on top though, and it still won't start. Took the time to check the spark this time, held a plug against the neg battery terminal while cranking, and I get nothing.

So, I'm thinking ecu (orange box) or coil (aftermarket) is fried. I don't know much about ignition systems, how do I locate the source of the problem? Preferably without buying a bunch of parts to test-swap in.

Thanks!

[68 RT]

Change the plugs usally once they are fouled that is it for them. 

[tricky lugnuts]

I'm by no means an electrical genius (I'm trying to sort through the same issues on my car) . . .

But, if after you clean the "fouled" plugs, you still get no spark out of them . . .

Try a test light at the negative terminal on the ignition coil . . . I believe the clip should be attached to the positive terminal of the battery.

When cranking the engine over you should see the test light "pulse" as the pickup coil in the distributor does its job, sending a signal to the ECU and back to the ignition coil . . .

If not, then you've got either ECU or pickup coil in distributor not doing its job.

[mhinders]

You can easily measure the coil, any lowest cost universal meter (multi-meter) will do it. It is somewhat unlikely that the coil is bad, unless your ballast resistor has gone bad and your coil has been overheating...
First:
Set the multimeter switch to 200 Ohms or something like that, it's not critical, place the 2 test leads between + and - terminal on the coil, you should read something between 1-2 Ohms, an aftermarket "hi-perf" coil will read lower.
Second:
Set the multimeter to 20000 Ohm (20kOhms) or similar:
Connect the 2 test leads between the - terminal and the cable terminal to the distributor...you should read something like 9400-11700 Ohms with an original Mopar coil, more if you have upgraded the coil.
Good luck,
Martin