Testing ecu without starting car? What else breaks when ecu fries?

[jredgo1234]

I fried my ecu when driving, one of the leaky capacitors blew out the bottom. That ecu was trash so i got another one. Now when i put the ecu in the car it still wont start. I figure one of 2 things:

-Either the ecu is bad (looks in good shape but i could be wrong)
Is there any way to check the ecu to see if it is good without having an engine that starts. I noticed the boost guage didn't click up to 0 when i put the key in and turned it to on. Isn't it supposed to. Thats the ecu right? What else should i look for?

or

-When the other one blew causing the car to shut off something else was fried ekectrically. I checked the 2 fuse boxes under the hood and the one with mpi bla bla. I also checked the one on the drivers side. Is there anything else that i should be checking.



Thanks

 

[JohnEagle]

i assume you got the computer used ? are you sure it is for your year make and model ? i know these are dumb questions but i have to ask. you should be able to plug it in and the car start.

 

[jredgo1234]

yes its a 1990 md145903 so it should work, used but looks in perfect shape. Any help would be appreciated!

 

[steve]

I noticed the boost guage didn't click up to 0 when i put the key in and turned it to on. Isn't it supposed to.

Yes a turbo ECU should. The two things I look for to tell me is the ECU is getting power and running are the CEL light turning on for five seconds and the boost gauge moving to 0. If neither happen then the ECU could be bad or it might not be getting power. If the CEL lights up and goes out but no movement from the gauge then I look at the board and make sure nobody pulled a fast one and stuck a N/T board in a turbo case.

Steve

 

[jredgo1234]

The CEL doesn't come on and the boost guage isn't going to 0. I'm assuming that this means that it is a bad ecu? Is there any other problem with the car (fuses wiring) that would have blown when the other ecu fried, and is now causing this new ecu to not get power?


Edit: Actually we can check off fuses as not a problem, i checked all of them.


I read that the ecu gets power in 2 ways, a main power that comes stright through from the ignition switch, and a small memory saving power supply from the fuse that controls the radio and interior lights. Since the fuses are good i don't know what else to check.

 

[jredgo1234]

Turned out to be a bum ecu. Thanks for the help steve

 

[steve]

You can check the MPI relay operation to make sure you have poewr to it and see if the ECU is trying to activate it. That process depens on the ignition switch working and the ECU so there are still failure modes that don't directly point to the ECU as the cause. Just a likely one.

EDIT: I see you found it was a bad ECU. Unless you have seen it work in another car you can't assume it's good.

Steve