Battery Draining from ECU circuit- Need some help

[Baird]

Hello,

I have a 91 Dodge Stealth.

The battery began draining overnight. After verifying that the battery was good, I borrowed a multimeter and found a draw of 1.2 amps that went to only .05 amps when the fuse labeled "Engine" was pulled. I've been getting by since then by pulling that fuse when I get out of the car.

I disconnected the MFI relay and there was no more excess current draw. After the relay was reconnected and the ECU disconnected, still no draw. I thought the relay could be bad so I replaced it, but that didn't solve the problem.

Anyone have some advice? Does the ECU need to be replaced or is there another component that could by causing this problem? I really appreciate and hints or ideas.

Thanks

 

[steve]

The DOHC Stealth and 3000GT ECUs are line the DSM's in that the ECU turns on/off the MPI relay in response to seeing 12v from the ignition switch. I believe the SOHC ECU also do the same thing but I don't have much exposure to them.

On the 1G DOHC ECU pin 62 is the input from the ignition switch RUN and START positions. When it's raised to 12v the ECU responds by grounding pin 108 which activates the MPI relay. About 10 seconds after 12v is removed from pin 62 the ECU should float pin 108 and the MPI relay should turn off.

Also like DSM ECUS the caps leak on the 1G 3S ECUs. The board that controls the MPI relay is much farther away from the caps on the 3S ECU than it is on a DSM ECU but I've still see the leakage make it all the way down to it.

 

[Baird]

Thanks for the advice. It was a little technical for me so I'd just like to make sure I understood. So are you saying the problem is likely with the ECU which is not turning off the relay?

Is there a way of testing it that you know of to be sure it is the ECU?

Thanks

 

[steve]

If the MPI relay isn't turning off it's either because it's bad, the ECU is bad, or signal from the ignition switch is bad.

Perhaps if you posted pictures of your ECU I might see something.

Does the MPI relay turn on as soon as you connect the ECU back up?

 

[AG 305]

how about a car that NOTHING works untill its turned on? all fuses are perfect. ECU issue?

 

[steve]

how about a car that NOTHING works untill its turned on? all fuses are perfect. ECU issue?

You need to sit down with the wiring diagrams from the FSM and a multimeter and start checking circuits starting at the battery.