Smoking ecu's

[T-rev]

Having some problems here. My Sr was running fine a day ago, making boost and pulling like a mother. Now it wont start. When I turn the key on, the fuel pump wont come on. I opened up the ecu box and found the circuit board was burned and looked like this:



this isnt my board but it looks the same. Thats why my fuel pump isnt coming on. It took me 2 ecus to find this out, so not really ready to think about blowing a 3rd one. Anyone had this experience before? This is a 1990, ex/ ka24e, with a S13 redtop, baked a #62 and an E5.

edit: fixed pic link
Modified by T-rev at 9:29 PM 7/16/2007

[T-rev]

UPDATE: Ive soldered the broken connection (pretty crude) also I replaced the extension wires I had running to the MAF since I read those have been a problem in the past, and mine looked like they got a little hot, but not melted.

Now the fuel pump will come one with the key, fuel to the rail, but injectors arn't firing. Got plenty of spark tho.

When I test the ecu, pin #36 (IGN ON) this is the lead that fried, so that must mean it had a dead short somewhere? Hopwever, it seems to be working alright now.

Is this connected to the problems: Pin #37 (TPS power out) right beside it, if I touch it with my test light, I get a short, it starts smoking the solder flux on the board right beside #36, but it wont light my test light. Whats going on there? Even does it with the TPS unplugged.

[josephg15]

i had this same problem...did you pull the eccs relay while the car was on? if you looks at the 240sx history there is a service bulliten on removing the eccs relay with the key on, may damage ecu?

[SpeedRacer1]

Check further in your harness, either a couple wires are crossed on accident or they may be melted together. I once worked on a guys car who blew 3 ECU's in the same place. Turns out his MAFS wiring had been fried together because it melted after being left running over the exhaust manifold.

[T-rev]

I didnt pull the eccs relay when the key way on, but thats good to know, thanks.

Both ecus failed while the car was running. Ill check the mafs pin to see if theres a short when I get home.

Would this cause a problem? I was trying to set the timing with a timing gun. I unplugged the tps while it was running, and then shot the timing gun. The timing seemed all over the map, so I got is as best I could to the 2nd from the right timing mark. And replugged the TPS. When I check the tps pin on the ecu w/ my test light I get a short, but no light. Any idea whats going on here?

[josephg15]

timing should be set second mark from the left...no idea why that happened to your timing gun. did you try using it again?

[T-rev]

The timing was my mistake, I read somewhere that the timing was 2nd from the last mark, somehow I thought that ment the right side.

Ive got another pinout diagram for the ecu, http://www.mys15.org/s15_tech/ecu.htmthis tells what the signal should be on each pin, so Ill get testing them tonight.

After thinking about it all day, Im sure its got to be a short on pin #36. I recently hooked up the 02 sensor, does it get its power from that pin?

[SpeedRacer1]

A short on any number of sensors could cause that circuit to overload and short. As mentioned before, look for wiring that melted or otherwise touched together somehow that shouldnt have.

[T-rev]

the injectors weren't clicking, and I found out why, this 25A fuse was blown.

this fuse is in between the battery and the 2 ECU backup power pins (46 & 109 I think) When the key is ON, both leads on the fuse are hot (IE when the fuse is out, both sides are powered)

That can't be good, this wire is also the power to the injectors, like the sohc harness

The car starts now, runs a little rough, but wont shut off, I have to pull the fuel pump relay because turning off the key or pulling this fuse does nothing. The short has to be somewhere around here, overloading the ignition switch basically running the car via the ecu?

[BEST1TUNING.COM]

If you have fixed all causes of the short, which for this problem is usually due to the MAF wire insulation melting and shorting then you will have to have a specific diode replaced in the ecu wich also was damaged because of the short. I do this all the time with ECUs damaged because of the same problem, If you have ECU's that have shorted in the same location, you can send them to me and I will repair them back to their original working condition. If you do not replace the diode, the car will not shut off.

[T-rev]

A diode! now why didnt I think of that? So I just checked that fat diode thats right beside the solder run that burned, and its a dead short.

Im not sure if I got the short circuit, Im a little gun shy now. So Im thinking about putting an inline fuse on pin #36, maybe 5A or less, that way I blow a fuse before it smokes out another ecu.

[BEST1TUNING.COM]

Not a bad Idea.

[PantherRacer]

So. This problem is caused by shorted MAF wires most often right.Well. I guess the GENIUS who did the swap in the car before I bought it really just...UGH!

Yeah, let me explain.The MAF wires are SOLDERED ONTO THE MAF. let me repeat this. No connector, THE MAF WIRES ARE SOLDERED TO THE MAF.

When we found the ecu was blown on the ignition ckt, we added a wire there to fix it, etc etc. I mean, I was worried about the diode also being burnt but I guessed that it was just from that wire burning.I'm glad to know THAT is why it wouldn't turn off. So I need to go check my maf wiring.I need a new maf.

[PantherRacer]

Just to add more insight to this problem, yeah it was the maf wiring shorted together. Somehow I now have fuel pump wiring problems, so I'm in the process of hard-wiring the pump.

[notslow]

[threadjack]Im from Kamloops but go down to Van oftenI will be visiting Van this week and leaving on the 31st. If you are in Vancouver/Burnaby/Coquitlam area at all send me a msg @ *edited* if ya wanna meet up.

-Kevin A.

kthnxbai[/threadjack]

Good luck w/ your ECU

*edit*nvm this thread is older than my underwear