Elecrical Gremlin

[R32 TT]

Hey guys, hoping for some hints about where to start looking for this.

Have an intermittent problem where I appear to have an complete electrical shutdown. Doesn't do it on Dyno or general driving, didn't do it at recent Powercruise. Only does it at a tight circuit sprint event on corners. Sometimes doesn't do it at all! At first I thought it was only right handers, but it has done it going left also..

Has done it once or twice a couple of years ago with previous engine build, car has had plenty of work during that time, and when the latest incarnation of the motor went in, it got new earths etc.

If you look at this screen shot of the logs, you can plainly see it losing voltage across and regaining it in quick succession. Doesn't appear to be just power to the Motec either, as when that happened - all my stock gauges were bouncing up and down erratically. So it looks like its 'further up the line'. This pulsing is new - it used to cut right out and then just return a second or so later. This is the first time I have been able to 'log it' since Motec appears to have stayed up long enough to keep logging.

I have searched a bit and seen threads about Alternator/fuses/reg etc.. but the problem I have with all this is that if the alternator were cutting out, there is still the battery to keep power. So it must be some sort of open circuit?

One thread somewhere suggested you can have a problem with the ignition barrel even?

Could it be a particular Relay that anyone knows as causing this kind of symptom?

So. Just looking for any brain-storming ideas from you guys who could say what things to check first. Hope to get onto this little gremlin over the christmas break and wanted some ideas and thoughts to make a plan of what to check first.

[StevenCJR31]

You have checked all your wiring and connectors? sounds like "loose wire syndrome"have heard of wiring being a tad short and only failing when under the stresses of racing (ie body flex)

[mad082]

might be a wire with a bit of wear on the outer insulation and when the body is flexing it is shorting out on the body

[t_revz]

so it looks in that pic like it faulted for about 10 seconds? what happened to the engine when it happened? im just thinking if the engine did die then the stresses on the car should have reduced quickly and the fault should have stopped much quicker then 10 seconds. how long does it usually last?

offer still stands to bring it down here for me to have a look

[R32 TT]

  On 18/12/2011 at 10:14 AM, StevenCJR31 said:

You have checked all your wiring and connectors? sounds like "loose wire syndrome"have heard of wiring being a tad short and only failing when under the stresses of racing (ie body flex)

Well, I've looked over them and looked for anything obvious yes. I've tried pulling/pushing on them with engine running etc, but can't get anything to fault.

  mad082 said:

might be a wire with a bit of wear on the outer insulation and when the body is flexing it is shorting out on the body

Yes, could be - I just thought that that kind of thing would almost certainly take out a fuse?

  t_revz said:

so it looks in that pic like it faulted for about 10 seconds? what happened to the engine when it happened? im just thinking if the engine did die then the stresses on the car should have reduced quickly and the fault should have stopped much quicker then 10 seconds. how long does it usually last?

Yep, dead right. On this particular occssion it was very diffent because it went on/off/on like that.. Engine lost all power, but 'sort of' kept running, backfired, ran rough, stalled etc. Remember I still had road speed and was using the clutch to keep it going as best I could to get it across the finish line. In the past it has just been a plain cut for a second or two and then bam, power comes back and stays. The first few times it did this I thought it was low fuel / fuel surge. But it ain't that.

  t_revz said:

offer still stands to bring it down here for me to have a look

You're a good man Trev, and I might still take you up on it. Just trying to get some ideas to check in the meantime.

[Nissan1986]

I have the exact same problem with my r33 Gtst s2, But my car stalls every time I hit a small bump. Sometimes when I hit a big enough bump it stalls won't start for a couple of seconds and then will. For some reason the airbag light stays on for about 15 mins, had an auto electrician look at it he had no luck all electrical seemed alright, he did mention something about immobiliser if you have one but I had it removed and that didn't do a thing. I could only assume electrical would be the problem do you think putting on diagnostics would display some kind of error message or have you had this done?

[R32 TT]

  On 30/12/2011 at 6:04 AM, Nissan1986 said:

I have the exact same problem with my r33 Gtst s2, But my car stalls every time I hit a small bump. Sometimes when I hit a big enough bump it stalls won't start for a couple of seconds and then will. For some reason the airbag light stays on for about 15 mins, had an auto electrician look at it he had no luck all electrical seemed alright, he did mention something about immobiliser if you have one but I had it removed and that didn't do a thing. I could only assume electrical would be the problem do you think putting on diagnostics would display some kind of error message or have you had this done?

Hey Robbie,

Frustrating isn't it... I still have not had a chance to look at the car in any detail due to holidays and people like, y'know, family, getting in my way! Hoping to get onto it soon and will def write back here what I find when I find it. I do have an immobiliser and this is a good place to start I think.

I haven't tried diagnostics simply because there is very little left that the std ECU is controlling - motec now has that job but the only thing its been able to tell me is that power goes missing! (duh!).

[R TUNE]

Make shore you have no loose random conections, i had a similer issue were i would lose power, not just electronics but from the eng as well. was found to be a random conection touching my alloy radiator.

[DVS JEZ]

Check the drivers side wiring loom above the front right wheel. May have worn/rubbed through

[R32 TT]

  On 01/01/2012 at 10:25 AM, R TUNE said:

Make shore you have no loose random conections, i had a similer issue were i would lose power, not just electronics but from the eng as well. was found to be a random conection touching my alloy radiator.

  On 01/01/2012 at 8:19 PM, DVS JEZ said:

Check the drivers side wiring loom above the front right wheel. May have worn/rubbed through

Hmm, thanks guys, I'll check for both. I would have thought though that anything 'touching' and shorting would blow a fuse.. But hey, not ruling anything out at the moment. DVS JEZ are you talking about inside the engine bay nearby fusebox?

[DVS JEZ]

Nope. Above the wheel. Jack the car up and look above the drivers side front wheel. U May see a wiring loom there depending if u have a inner gaurd or not.

How low is ur car?

[R32 TT]

  On 02/01/2012 at 11:32 AM, DVS JEZ said:

Nope. Above the wheel. Jack the car up and look above the drivers side front wheel. U May see a wiring loom there depending if u have a inner gaurd or not.

How low is ur car?

Not super low. 355mm center of wheel to guard, but it does see track time mostly, and this is where the problem happens so I'll have a closer look there - cheers, just the kinds of tips I was looking for.

[bluey33]

I have the same issues. Only on handbrake entries in car, will shut off then come back to me a split second or several seconds later. Ended up finding battery terminal loose. Couldn't pull it off the battery post but could spin it with a fair bit of force. Tightened up lower on post, still yet to test it. Hope that's it anyway.

Would not happen on transitions.

[DVS JEZ]

Does urs lose electrical power or is it fuel surging?

[bluey33]

Electrical power. Loose everything, power steering in particular which sucks when u got one hand on wheel and other on handbrake. Then when I go to get on gas nothing for quite some time sometimes. Weird cause like i said only and handbrake entries. Does it left hand or right hand aswell.

Has turbo timer but not hooked up to handbrake so that isn't an issue either.

Edited January 3, 2012 by bluey33

[R32 TT]

  On 03/01/2012 at 3:40 AM, bluey33 said:

Electrical power. Loose everything, power steering in particular which sucks when u got one hand on wheel and other on handbrake. Then when I go to get on gas nothing for quite some time sometimes. Weird cause like i said only and handbrake entries. Does it left hand or right hand aswell.

Has turbo timer but not hooked up to handbrake so that isn't an issue either.

Well it should not matter if the battery is connected or not.. "shouldn't". Once the car is started all electrical power comes from the Alternator and the Battery just becomes another load, like headlights.. ie because it is being charged.

You should be able to start your car, then pull the battery cable off the terminal ad everything should keep running...

[t_revz]

  On 03/01/2012 at 12:18 PM, R32 TT said:

Well it should not matter if the battery is connected or not.. "shouldn't". Once the car is started all electrical power comes from the Alternator and the Battery just becomes another load, like headlights.. ie because it is being charged.

You should be able to start your car, then pull the battery cable off the terminal ad everything should keep running...

disconnecting should make the alternator overcharge as it cant see any voltage from the battery. depending on how high the voltage gets to things might start cutting out .....or blowing up

[R32 TT]

  On 03/01/2012 at 10:38 PM, t_revz said:

disconnecting should make the alternator overcharge as it cant see any voltage from the battery. depending on how high the voltage gets to things might start cutting out .....or blowing up

Ah ok. Well I didn't know or think of that.