melted cable - now cant start car

[istoo]

Went to fix one problem and made another. I was having a look at my N75 last night just before dark, took the air box off moved the cable that feeds the N75 and MAF out the way and tried to remove the N75 but it was juts gettgin too dark to see. So put it back together and decided i would go for a wee run. 3-4 miles nothign more, halfway through thge car cut out. flipped the bonnet. Immediate problem, the cable that should run down the side of the airbox, i forgot to tuck away it has touched the exhuast and burned.

Cleaned the cables up this morning wrapped in insulating tape each of the burned ones, 4 of 8 were through to bare copper. Only one has 1 or 2 strands of copper gone nothing significant at all. Checked all the fuses, none blown which i was surprised at. Start the car, and doesnt fire at all, turns over ok but not firing. Worried i may have fried the ECU any suggestions?

photo of my stupidity.

[S2central.net]

Fuses should have protected from such a nasty mishap and it would be a bit crazy if the ECU wasn't protected by internal circuitry from such a short circuit.

To see if the ECU is alive - see if you can pull fault codes and/or try output tests. Check s2central.net for the pinout on the MAF plug so you can see if it is still getting +12V.

There should also be 5V on outer two pins of the 3-pin hall sender plug when the ignition is on.

[istoo]

thanks for hte quick reply, will borrow a multimeter tonight.
I dont have an OBD cable for this car, but i have a blink code reader, not used it for this car (urS4) but will give it a go assuming its under the steering wheel as well?

To top it all off my wife is just of of hospital after a major op, so i have very little time. Not the most clever thing i have done.

I thought the car should start with the MAF disconnected?

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forgive me i cant see for looking, where is the link for "Check s2central.net for the pinout on the MAF plug"

[Smiley]

Yes, MAF and N75 are not needed to start the engine. Hall Sensor and one of the sensors near the flywheel are worth checking..

http://www.s2central.net

[Smiley]

http://www.s2central.net/motronic_02.html

[S2central.net]

It will likely not start if MAF wiring is munged though... you'd best buzz it all out and make sure nowhere else is melted.

[istoo]

cheers will try this out tonight and see where i get too.
Going to try ECU fuses as well, make sure they havent popped.

[S2central.net]

I'd wager Fuse 27 and/or 28 first of all. Check the MAF signals against this - http://www.s2central.net/ds_G70.html

[istoo]

I'd wager Fuse 27 and/or 28 first of all. Check the MAF signals against this - http://www.s2central.net/ds_G70.html

I went through all the fuses this morning and they all looked intact! Thus my, oh sh*t moment, will have a second look some are not audi OEM fuses and harder to see in half light.

Report back later tonight/ tomorrow morning!

Thaks for all the suggestions and help so far, really hoping its a simple fix.. everything crossed!

[S2central.net]

My intuition says it will be something stupid / overlooked... ECU *should* be protected from this sort of badness.

[istoo]

My intuition says it will be something stupid

Damn rumbled again!

[istoo]

something simple. The 5 amp fuse beside the ECU had blown, replacedand the car started fine. ont he flip side the clean out of hte N75 and reset of the ECU i swear the car is boosting better, hitting 20+psi on full load.

Thanks for the prompt responses.

[Knight Rider S4]

Ian I have off cuts of loom which will cover that area if you need it ..can splice it in and make all neat again


Cheers

Steve

[istoo]

thanks steve, add that to the list!
If your free soon might fire down for a day again

[yodaboy]

Glad you got it sorted

My N75 was given a good clean last week also.....I cant get over how much power these 5 cylinder turbos kick out its only when they are running perfect do you realise whats on offer......Ive been embarrasing cars with much bigger engines and bhp......