bad ecu blown mpi fuse?

[AUTOMODSGST]

I been having trouble staring my car it starts some times and other days it just does not ( good thing is not my daily ) so today I started to double check everything and I found that my cel was not coming on when I was attempting to start the car, so I checked fuses and connections and I found that the MPI fuse was blown, I changed it and tried starting the car again, CEL came on for 5 sec and the car turned on I shut it off right away and tried to start it back on and it didn't I checked the MPI fuse again and it was blown I looked for another fuse I couln't find a 20 amp so I installed a 30 amp one (the pink ones) and the car started again I had it on for a few seconds and then ...... it started smelling like burnt wires (good thing my dashbord is gutted) I have all kinds of space there, and it was the harness from the ecu that was starting to burn shut the car off (stupid tt) would shut it off so I turned off the tt manually and it shut off, the harness did not catch fire but it did get burned a little so now I don't know what to think; the car ran perfect all day yesterday until this happened I will try to post some pictures of the ecu and wiring but I need your help troubleshooting this thing. thanks and sorry for the long post I think is the ecu but would the bad ecu blow the MPI fuse?

 

[FalleN4ng31]

Judging solely by your pictures of the wiring, I'd be looking for a short in the wiring.

 

[toybreaker]

That's why you NEVER replace a fuse with one that has a higher rating.

The o2 heater power wires are now all melted, infused and entwined.

This happens because the 02 harness gets hot/oil soaked/basted in service. This causes the wires to become brittle and the insulation to crack.


Shake it just right, and conductor of the 02 heater wires will become intimate with the outer shielding/ground, and a short circuit will result

... popping the mpi fuse




Fuses are there to protect the wire, and by replacing that fuse with a higher rating, you exceeded the current capacity of the wire, and she got melty.







You will have to strip the loom off the harness all the way back to the ecu and carefully inspect the wires to be sure, but the good news is you *probably* didn't hurt anything else.

You will need to fabricate a new o2 wire set, including the heater and signal wire and provide some noise shielding, but that harness is most likely saveable with a little effort.



... If it makes you feel better, I only know replacing a fuse with a higher rating results in tears is I did it myself way back in the day. (had a girl with me and augered my z into a snowdrift showing off. Replaced the burnt headlight 15 amp fuse with the only thing I had, a thirty ... didn't need headlights after that ... the smoldering harness lit the way ...

... you'll only do it once.


Good luck with the fix


[edit] Oh, get that ecu looked after!

Looks like original caps are seeping toxic spooge. That Boric acid and Ammonia salt will do all kinds of bad things to the ecu board if the capicators are not replaced and the board correctly treated to remove the residual contamination.

 

[AUTOMODSGST]

That's why you NEVER replace a fuse with one that has a higher rating.

The o2 heater power wires are now all melted, infused and entwined.

This happens because the 02 harness gets hot/oil soaked/basted in service. This causes the wires to become brittle and the insulation to crack.


Shake it just right, and conductor of the 02 heater wires will become intimate with the outer shielding/ground, and a short circuit will result

... popping the mpi fuse




Fuses are there to protect the wire, and by replacing that fuse with a higher rating, you exceeded the current capacity of the wire, and she got melty.









You will have to strip the loom off the harness all the way back to the ecu and carefully inspect the wires to be sure, but the good news is you *probably* didn't hurt anything else.

You will need to fabricate a new o2 wire set, including the heater and signal wire and provide some noise shielding, but that harness is most likely saveable with a little effort.



... If it makes you feel better, I only know replacing a fuse with a higher rating results in tears is I did it myself way back in the day. (had a girl with me and augered my z into a snowdrift showing off. Replaced the burnt headlight 15 amp fuse with the only thing I had, a thirty ... didn't need headlights after that ... the smoldering harness lit the way ...

... you'll only do it once.


Good luck with the fix


[edit] Oh, get that ecu looked after!

Looks like original caps are seeping toxic spooge. That Boric acid and Ammonia salt will do all kinds of bad things to the ecu board if the capicators are not replaced and the board correctly treated to remove the residual contamination.

thanks for your reply and yes that is exactly what happened those wires got intimate and yes the fuse blown, I did a little testing on wires and fix whatever looked bad and tried it again with a 20 amp fuse crossing my fingers that it would start and lucky me it did, the car started and no cel came on fuse still good so yes I am 99% sure it was a short circuit as you said and yes I need to get that ecu fixed because I think that is the reason I am having trouble starting the car but I might just get an eprom everything looks to be working normal thanks again

Does anybody knows how much do they charge to replace the ecu caps and who does that kind of work?
there is a guy selling a 1990 eprom ecu do you guys thing that would be a good investment he's saying is already socketed and would it work on my 92 tsi?

 

[clipto]

Contact these guys they can get you setup ECMTuning, Inc., looks like a mess hope you get it fixed.

 

[HIGHPSI4]

When you fix the 02 wiring be sure to keep the shielding in place. Get the ecu fixed and maybe your are ok.

 

[AUTOMODSGST]

thanks guys the car is ok it started yesterday after I fixed the damage wires, when you talking about the shielding what is that exactly thanks guys