98 A4 2.8 No start/engine timing fuse issue???

[Kodymfk]

Hello, I have a 98 A4 Avant 2.8 that is having a running issue. A buddy was installing a sub woofer and accidentally touched the power wire somewhere he shouldn't have. Current issues are:

It doesn't turn over but it cranks no problem (have got it to run once or twice with pedal at WOT, saw maybe 3000 rpm). Doesn't really like to start.

It blows #32 fuse (engine timing fuse 20a) every time the key is turned to on.

Tried swapping the ecu for identical one in fear it damaged ecu.

Battery wont charge past 2.0v after hours of charging (replaced battery as well now).

Would like to add that I've checked all other fuses and large ones that i'm aware of under kick board and such. They appear fine. Also I couldn't get my vcds cable to read the car? Is this normal for these cars (first me5 car iv'e really touched). I have hex-can cable. When the car does start, it runs very rich at very low idle. Haven't got it to do much. Any and all help is greatly appreciated. Thank you in advance.

[bmos]

So what did he touch the power wire to? Should have been pretty obvious when it happened...

Also what power source was he tapping into? Straight from the battery?

[Kodymfk]

So what did he touch the power wire to? Should have been pretty obvious when it happened...

Also what power source was he tapping into? Straight from the battery?

He tapped straight from battery. It also had a fuse connected to it (50a). He didn't specify what he touched either. I do know I cannot get the #32 (engine timing) fuse to NOT BLOW when I turn the key on.

[bmos]

Ouch, 50A is a lot of amperage. He doesn't know what he shorted it against?

Was he running the wire through the ECU box?

[Kodymfk]

Ouch, 50A is a lot of amperage. He doesn't know what he shorted it against?

Was he running the wire through the ECU box?

He has no idea, seems very odd if you ask me lol. I need to find some leads on where to start looking. I need to figure out exactly what is ran through fuse#32. I'm curious of two insulated wires got to hot and melted when the power issue happened.

[Nollywood]

You've got a shot circuit / high resistance.

Where would depend on what your friend shorted the power cable against, and where the power cable is actually tapped from.

[Kodymfk]

You've got a shot circuit / high resistance.

Where would depend on what your friend shorted the power cable against, and where the power cable is actually tapped from.

He tapped the power wire directly from the battery post with an inline 50a fuse that from battery post, directly to amp (In back of hatch area). Are there any other relays that control engine timing that could be inspected for damage?

[bmos]

Just check for ground on both sides of fuse 32. If you find ground (which shouldn't be there) you know the wire is shorted to ground. Then you can follow the diagram back from there unplugging each connector once at a time until you've isolated where the short to ground is.

I'll PM you a diagram.

[vtraudt]

Just check for ground on both sides of fuse 32. If you find ground (which shouldn't be there) you know the wire is shorted to ground. Then you can follow the diagram back from there unplugging each connector once at a time until you've isolated where the short to ground is.

I'll PM you a diagram.

With 32 fuse wiring diagram in hand, check what else is in the circuit. "Engine timing" might just be the VVT (cam chain tensioner)? Can't think of another user. If so, unplug the VVT actuator and measure fuse. Still short to ground? ==> wire. No short? ==> leave VVT unplugged (not needed for anything) and see if it starts.
But even with fuse 32 out, car should start (but check 32 circuit if there is anything vital in there).

[Kodymfk]

Just check for ground on both sides of fuse 32. If you find ground (which shouldn't be there) you know the wire is shorted to ground. Then you can follow the diagram back from there unplugging each connector once at a time until you've isolated where the short to ground is.

I'll PM you a diagram.

Thank you for the pm, I appreciate it. I will be looking over it.

[bmos]

After looking at the diagram, it looks like that fuse might be the direct feed to your ignition coils. (It's labeled differently on the diagram so I'm going to check it when I get my car back).

Try unbolting the capacitor by your ignition coils and wrapping it in electrical tape. If he overloaded it it might have shorted to ground?

[Kodymfk]

After looking at the diagram, it looks like that fuse might be the direct feed to your ignition coils. (It's labeled differently on the diagram so I'm going to check it when I get my car back).

Try unbolting the capacitor by your ignition coils and wrapping it in electrical tape. If he overloaded it it might have shorted to ground?

Will do, Thank you for the help. I do recall seeing the a small resistor type device near the coil pack setup.

[bmos]

The little box by the coilpack is a capacitor that helps filter out high voltage spikes caused by the coil's operation. If it is damaged by excessive amperage, or in any way that causes an internal short, it will connect the fuse you're blowing directly to ground which would obviously blow the fuse immediately.

[19birel]

I was blowing the same fuse on my 1.8T, check your coil pack wiring, mine was brittle and broke, but yours could be fried at some point.

[Kodymfk]

The little box by the coilpack is a capacitor that helps filter out high voltage spikes caused by the coil's operation. If it is damaged by excessive amperage, or in any way that causes an internal short, it will connect the fuse you're blowing directly to ground which would obviously blow the fuse immediately.

Awesome, I appreciate the help greatly. This is a really good start to getting this issue solved. Will tear into the coil pack area tomorrow and see how it looks. Will try wrapping it in as well like you mentioned.

- - - Updated - - -

I was blowing the same fuse on my 1.8T, check your coil pack wiring, mine was brittle and broke, but yours could be fried at some point.

Planning to checknit for sure. Did you end up replacing your whole coil pack setup along with wore harness?

[19birel]

Planning to checknit for sure. Did you end up replacing your whole coil pack setup along with wore harness?

Kept the original coil packs and just replaced the coil pack harness with a used unit from a donor car.


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[Kodymfk]

The little box by the coilpack is a capacitor that helps filter out high voltage spikes caused by the coil's operation. If it is damaged by excessive amperage, or in any way that causes an internal short, it will connect the fuse you're blowing directly to ground which would obviously blow the fuse immediately.

Do you know where to source the little black capacitor? I can't seem to find one online. Going to search for a part # on it tomorrow.

[bmos]

Do you know where to source the little black capacitor? I can't seem to find one online. Going to search for a part # on it tomorrow.

I haven't been able to find one either, I think you have to buy the whole harness :(

I wouldn't replace it unless wrapping it in tape fixes it, 'though.

[Kodymfk]

I haven't been able to find one either, I think you have to buy the whole harness :(

I wouldn't replace it unless wrapping it in tape fixes it, 'though.

I managed to get someone to cut it off a harness and send it to me for $15 last night. Going to try swapping that out along with inspecting coil pack unit for damage and replace that if needed as well. Someone did mention to me, we don't need it unless we listen to alot of A.M. radio? Wasn't sure what he meant by it but it sounded like we could totally bypass it if we wanted to?.

[bmos]

I managed to get someone to cut it off a harness and send it to me for $15 last night. Going to try swapping that out along with inspecting coil pack unit for damage and replace that if needed as well. Someone did mention to me, we don't need it unless we listen to alot of A.M. radio? Wasn't sure what he meant by it but it sounded like we could totally bypass it if we wanted to?.

You can't bypass it but you could cut it off and just seal the end.

Its purpose is to block high voltage which causes radio interference (not just AM though, any use of the headunit in my experience).

[Kodymfk]

You can't bypass it but you could cut it off and just seal the end.

Its purpose is to block high voltage which causes radio interference (not just AM though, any use of the headunit in my experience).

Ahh, I see. Do you know is these 98 A4's have any sort of security systems in the radio as in for example, could an aftermarket ever prevent you from starting the vehicle like in some of the later models?

[Kodymfk]

I ask because, there was an aftermarket radio installed but its currently uninstalled at the moment. It ran fine with aftermarket radio before. I uninstalled all aftermarket parts though to rule them out as a problem currently.

[bmos]

It shouldn't although I don't have experience with aftermarket h/u in B5s.

I just noticed the part about not being able to connect with your scan tool... You might want to read this.

[Kodymfk]

It shouldn't although I don't have experience with aftermarket h/u in B5s.

I just noticed the part about not being able to connect with your scan tool... You might want to read this.

Good call on the radio issue. This is more than likely my issue with obd communication. Going to read it and get the k line connected back up.

[Kodymfk]

So I fount part of the no start issue. I didn't think to check under them for I originally was able to get the car to run just it didn't run right, so i figured coils were all fine lol. I was wrong. I ordered a new one today and should have it tomorrow to try out. How ever, The capacitor was no good so I plan to cover that up until the replacement one shows up then re-wire it up. For now it will just be removed and shielded.

[bmos]

So I fount part of the no start issue. I didn't think to check under them for I originally was able to get the car to run just it didn't run right, so i figured coils were all fine lol. I was wrong. I ordered a new one today and should have it tomorrow to try out. How ever, The capacitor was no good so I plan to cover that up until the replacement one shows up then re-wire it up. For now it will just be removed and shielded.

Jeez, that's certainly part (if not all) of it.
I hope your modules are OK!

[Kodymfk]

Jeez, that's certainly part (if not all) of it.
I hope your modules are OK!

Everything seems fine so far. Have made plenty of test drives since replacing.