My ECU is fried...got some ?'s
 

i took apart the ecu that has been giving me alot of trouble and found that the things that bolt to the case inside are all burned up. Does anyone know what they are for and why they would get fried?

to make it more clear they look like thin black boxes that are held on to the inside of the case by tiny nuts.

First guess - battery polarity accidentally reversed.

For a replacement, maybe start with the parts forum.

well the thing is the car still ran DECENT and i never switched the polarity. I have a spare ECU in the car right now but its not in much better shape. At the moment im not really concerned with what blew them i just want to know what they are and what purpose they serve

I'd first check your primary & chassis grounds.
If they are not perfect, the ECU's grounds start to see load that they were not meant for.

i bet that is what those are.... where should i install a new chassis and primary ground?

BTW i always just figured my car was grounded good because ive never had the 3800rom hesitation. i guess thats what i get for assuming anything about an RX-7

To see what it does, go to pages 32-34 >> click here

i have the FSM and it doesnt saying anything about what the things that are burnt do...all it gives is what each pin does

To match functions with PCB components, you have to trace the circuit on the board, from the component output to the connector pin.

The ECU uses low voltage signals from sensors (like the TPS & the boost sensor).
Most of these sensors have their own ground wires, but if the primary grounds are the least bit weak, the sensor grounds try to carry the noisy spark and alternator loads also. The ECU tries to compensate & goes nuts.
The cheesy firewall to bell housing ground just clips on. Replacing it with a heavy gage wire with eyelets & bolts is a good start.
I have also seen improvements by adding a ground from the spark coil mount to the alternator frame.

ok ill go ahead and try some of those grounds im not really sure if the components are bad or not, its just on the under side they look like they have been getting very hot

here are some pics of what im talking about...

you can see the things bolted to the wall of the ECU
www.cafes.net/rotory/problems/000_0065.jpg

another....
www.cafes.net/rotory/problems/000_0066.jpg

and this is a shitty pic of the bottom side...you can barely see where it is burned
www.cafes.net/rotory/problems/000_0068.jpg

all of these little things bolted to the wall are burned on the underside of the board. im sorry to use the crappy terms such as "little things" but im not a good electrician. but i do have a kick ass fluke DMM so i can test some shit, i just dont know how.

I'll bet that with good primary & accessory grounds, many of your gremlins will go away.

ok so if i go out and put 4 brand new grounds on my car and if you dont mind could you be pretty specific, like where on the bellhousing....which 4 do you recommend sureshot? And BTW thanks for the quick responses and awesome advice.

anyone looked at those pics? i think ive got the grounding part understood, im going to do all that tomorrow.

Ok those are transistors, most of them. That green one may or may not be. The fact that they are burned means they are absorbing more power than they are supposed to be, which could be a grounding issue or it could be another problem. If they are only slightly burned (e.g. connections still solid, board brown but not black, etc...) and the units themselves look ok then you might be all right. The only way to properly tell is desolder, figure out what kind of transistor they are supposed to be, and get a tester for that kind of transistor. Most trans. testers won't test transistors that have resistors internally connecting the base and emittor or collector, and most transistors in the ECU have those, so you need a special transistor tester. Depending on your model of fluke (I'm not sure tho) it might be able to do it read the manual and find out. Otherwise you're stuck going through each ECU pin and checking it according to the FSM procedure. :-/

where in the FSM does it tell how to test each pin...i have a FSM here in front of me but it doesnt really give a description of how to test it while its out of the car. And i think i might be ok because the board is a little brown on the underside but not black and the components themselves look fine except for that resistor that you can see in the first pick is supposed to be blue but it is gray..thanks for the reply man ive been dying to know what those things are.

No you have to test in the car, bro. So you can see what the output of each device is while the unit is powered up. ;)

Yeah no prob sounds like the board should be good. That resistor might be toast but those are totally easy to replace. Figure out what its value is (post up your ECU number and maybe someone has that same number and can get you the resistor value) then just buy a new one and switch them out. ;)

cool well i suppose the next few days will be full of ECU testing after i complete my grounding project. i have an N333 its an 88 TII there are some other resistors in there of the same type so i guess i can test those. im considering buying a spare unit from opelbits but i want to test mine to see if its nessecary

Those are your injector drivers. Have you been swapping injectors? (high/low impedance)

-Henrik

ecu
 

I'm going throught he same shit with my ECU, but i couldn't go to radio shack cause they did not know how to help me, so I tried to get another ecu from the junk yard and tried to fix one with the other.
BTW, how much does it cost to puchase a new ECU, or to get it repaired.

Re: ecu
 

i havent been swapping injectors...im the 3rd owner though and hit has had a rebuild...im pretty sure i asked someone and they sa i had the right injectors...my secondaries are red.

bump

You sure they're red? From www.rotoryressurection.com

Year type impedance plug style plug notch position flow rating color part number
84-85 13B NT low square center 680cc orange 195500-0900
86-87 13B NT low square center 460cc red 195500-1350
86-87 13B T low square center 550cc tan 195500-1370
88 13B NT high square offset 460cc purple 195500-1350
88 13b T high square offset 550cc purple 195500-1370
89-91 13B NT high oval center 460cc red 195500-2010
89-91 13B T high oval center 550cc purple 195500-2020

pri/sec should be same colour btw.

-Henrik

Go to my ECU thread here:

https://www.rx7club.com/showthread.p...hreadid=230199

I have schematics posted for an n/a ecu. The turbo ecu is seems to be pretty much same thing, but with a different program and a few more components.

Look at what components are fried and then trace those back to the correct ECU pin. Then check to make sure that pin isn't shorted to 12V or ground.