Why does it EAT ECU's?

[Vegas_Nick]

FINALLY got the tired old 318 running. Good news is no knocks, no smoke. Bad news.... it has ate two ECU's in two days. I am running the following:

MSD blaster II coil with the inline ballast resistor as recommended by MSD

Four pin stock ECU. No ballast resistor.

All wiring is new.

I have assured the ECU has a good ground. Running voltage is just below 14 volts with the alternator on line. ECU gets warm but not too hot to touch. Runs about 45 minutes then no spark. Verified by swapping in new off brand ECU from Oreilly's.

At this point, I am thinking about wiring in a GM ECU since they are half the price of the Mopar. FWIW I have an orange box on the way but I am almost scared to plug it in.

Any ideas or recommendations?

[Vegas_Nick]

I mean this mod BTW:

http://www.dodgetalk.com/forums/showthread.php?t=203358

[justcruisin]

The most common cause of ecu failure is excessive current draw. I would see if your coil is to spec - you shouldn't be blowing them with that coil and a ballast, check your wiring is right. Extra wide plug gaps and high resistance leads can make the coil work harder - drawing more current but that wouldn't grenade a controller in a day. Most probably it's bad controllers.
I have been running a rev-n-nator with the blaster 2 and ballast for 5 years, no problems.

[Vegas_Nick]

The most common cause of ecu failure is excessive current draw. I would see if your coil is to spec - you shouldn't be blowing them with that coil and a ballast, check your wiring is right. Extra wide plug gaps and high resistance leads can make the coil work harder - drawing more current but that wouldn't grenade a controller in a day. Most probably it's bad controllers.
I have been running a rev-n-nator with the blaster 2 and ballast for 5 years, no problems.

Thanks man! The one from Oreilly's even had a fake transistor on the case with cheap chinese insides!

[68CoronetRT]

Are you running an MSD Box like a 6al or something?

[Vegas_Nick]

Are you running an MSD Box like a 6al or something?

No, just the standard ECU from O Reilly with the MSD coil.

[Vegas_Nick]

So my Engineer brain got the best of me. I built this real quick:






Started right up and ran just fine!! We'll see how it does next week when I finally get to drive it.

I did notice that the alternator is putting out 14V. The ECU is seeing 14V in and 12V on the coil- side so I am guessing there is some heat generated in voltage reduction that maybe the cheap ECU didn't like.

[A383Wing]

the ballast resistor is only for the coil, not the ECU...the ECU always gets full battery voltage

[Vegas_Nick]

Correct. That is the way I have it wired.

[justcruisin]

The + to the igniter is a different circuit to the coil - at the igniter (ecu), when you read the voltage at the igniter for the coil - you are reading the voltage through the path of the ballast and coil where as the + on the igniter is from an ignition supply and consequently is alternator regulating voltage - 14v - nothing to do with internal losses in the igniter. All the igniter does is switch the coil to ground, same as a set of points, that's why it is important to have a good earth and a heat sink like you have made, that's the path of the coil current.

[Vegas_Nick]

The + to the igniter is a different circuit to the coil - at the igniter (ecu), when you read the voltage at the igniter for the coil - you are reading the voltage through the path of the ballast and coil where as the + on the igniter is from an ignition supply and consequently is alternator regulating voltage - 14v - nothing to do with internal losses in the igniter. All the igniter does is switch the coil to ground, same as a set of points, that's why it is important to have a good earth and a heat sink like you have made, that's the path of the coil current.

I'd expect to see about .7V loss through the transistor that switches the coil... but more my concern was if the 14V was too much for the control module.