91 Laser no start

[tempfixit]

This is my neighvors car. 91 laser 2.0 Turbo with manual trans.

The other day he installed a new battery. The car ran for approimetaly 5 minutes and died and would not start. Tried again today would not start.

Check fuses OK.
Checked for spark OK
Sprayed carb cleaner in throttle body and it ran until cleaner was burned up.

Checked codes with a analog voltmeter and got the dreaded 12 volt steady reading.

Checked the fuel pressure switch that is in the center console, it checked OK.

Rmoved the ECM, it smells burnt.

What could have fried the computer?? Where to start looking for problems??
Will the fuel pump itself fry the computor??

Working on vehicle in the snow bank in WI.

Any and all advice is greatly appreciated

[gthompson97]

If he accidentally hooked up the battery backwards right away he could have fried the computer. Or sometimes they just burn out on their own when they get old. Hell, the car is 17 years old. Other than that, maybe the alternator regulator went bad and fried the computer. There's a laundry list of things that could have caused it. Electrical problems are always fun.

[JoeShmoe]

With the right (actually wrong) circumstances, anything can fry the ECM.

[tempfixit]

Thanks for input. One thing he did tell me was that while the engine is idling it loops ( rpms changing constantly) He says the Haynes manual states this can cause problems. Could this have been the cause of the computor being fried??

Thanks

[tempfixit]

I did talk to my neighbor tonight and he told me that he hooked the negative cable first then the positive cable. Is this what you meant by backwards?? If this did fry the ECM why would it run for about 5 minutes before dying??

Where should we start looking for a short problem?? Any ADvice would be greatly appreciated.

LS