Brettmck10

Hi all

My subaru bugeye recently dropped a cylinder. No.3 coil had failed so I replaced it and it was fine. Couple days later it went again so I swapped the plugs and coils for a new set I had. Again a couple days later no.3 went again. When I say it went I mean the coil actually blew up and melted. Replaced it again and monitored the temp over the coils when it started up and it was heating up really quickly which lead me to believe it was an electrical issue. Removed the engine loom and tested for continuity , all ok ! Then I done an insulation test with a megger and found a short between the earth, trigger for coil 4 and the injector as there was corrosion in the plug. Cleaned it all up but couldn't see why that would have affected no.3.

Put the loom back in today , on all 4 cylinders. The temp over each coil were all roughly the same and slowly increasing which was fine and it ran perfect ticking over for 10/15 minutes. I then went to cable tie some wires above the ecu to tidy it up a bit and boom the coil blew again and this time it also blew the ignition fuse. I checked the ecu for any damage or smells with nothing apparent and also checked the ecu plugs for any loose pins and again any corrosion but nothing.

Has anyone got any ideas or came across a similar issue ? I will disconnect everything and megger the loom from the ecu to the engine bay but other than that I'm stuck.

Thanks for your time guys

Brettmck10

Engine has also just had a full rebuild but problem started before this

Brettmck10

When it is up to temperature it also runs fine !

sti-chris

So I don't know the answer but lets look at how these work.

The coil packs has a constant voltage and the when pulsed it will operate.
It has 12 volts and I take it the coil pack is a transformer to bump the voltage to say 50+ thousand volts when pulsed, this then fires the high voltage down to the plug which arc's across the gap, hey presto we have a spark.

So if you are blowing up a coil pack then something must be right out of sorts, what if the coil pack was constantly getting a pulse from the ECU ?

Could you take a plug lead from coil 3 and test it on a plug?

can you try another ecu ?

Hitting and hoping for you buddy?

Searched and come across this http://www.audi-sport.net/xf/threads...g-coils.87019/

Okay its not a scooby but seems right bad wiring can cause issues, another forum I seen same fault different engine turned out to be knock sensor

Brettmck10

Hi Chris , cheers for your reply. I could understand it blowing if it was getting a constant pulse but that's the annoying thing. It runs perfect when it's up to temp. It is just strange how it seemed to blow tonight after moving the wires above the ecu. I thought it would be a loose pin or a bare wire but I couldn't see a thing.

I have taken the plug and coil out of no.3 and it sparks fine.

It's got to be the trigger wire though or the ecu. The 4 coils are all fed from a
Common 12v supply and all go to a common earth back to an earth mount on the manifold underneath the header tank.

Every other coil is fine !

I am going to megger the loom from the engine harness back to the ecu tomorrow and hopefully there's a short between the supply and the trigger haha, it will be cheaper than replacing the ecu

Cheers !

sti-chris

If its temperature related this could indicate either a bad connection or wire as resistance changes dependant upon heat etc, putting a megger to check this isolation wouldn't be a bad idea

Brettmck10

Well I meggered the engine loom and found a fault , albeit not the right one lol. Started it up and monitored the temps and they were all the same , wiggled the wires above the ecu then bang away it goes again, another £60 lol. This time the ignition fuse also went though and it hadn't done that previously. the fuse is rated to 15A and to blow that I thougt the pins must be loose in the plug or something but still doesn't look like anything is wrong! oh the joys of scoobs haha

Brettmck10

Meggered the loom between the ecu and coils and all checked out ok so can't be the wires, the temp gradually increases from start up to about 90 until I cut it out then started it again and then it was fine. My guess now is the ecu is faulty and is triggering it all the time ? I'm sure I read somewhere before that the ecu swaps from initial start up mode to a running mode and when it starts it draws everything from
The battery. Anyway looks like I'm sending the ecu away

sti-chris

That's a pain, certainly not a common one that I have seen on the forum. I take it no fault codes on such like as stored on the ecu ?

Brettmck10

Nothing I'm afraid , will phone gems on Monday and see about getting it sent away. I'm really hoping there's a fault because if not I'm really clutching at straws haha

sti-chris

Cant seem to find much on this to be honest.

https://www.scoobynet.com/general-te...rning-out.html

You might have a poor ground somewhere. Where are the critical grounding points on the engine? Check ground straps, these are known to fail or need cleaned up.

What plug's are you running is is PFR7B ? or 6B both fine.

Brettmck10

What do you mean by plus Chris ? Yeah all he earth straps are fine. I've tested all the earths throughout the loom and they are all fine. The live and earth wires for the coil plugs are all off a common line and the earths all go back to an earth point on the manifold. There are also spare earth straps on the car sonesrthing is definitely
Not an issue as I know how earth critical these things can be lol

360ste

iTrader: (1)

Be interesting to find the cause as I run a GEMS on my bug STi. Are there any signs of a water leak as when hot things may expand stopping a leak but could also cause a leak.

Brettmck10

No leaks at all ! I emailed teg sport and got a reply saying that they had the same issue with a gems ecu years ago and this would be the second time they've heard of it. They resolved it by putting a resistor in the coil feed wire which I could do but I'd rather find out why it's doing it now all of a sudden. Very strange

360ste

iTrader: (1)

Steve Simpson mapped my ECU. I had one coil pack fail many years ago funnily that was whilst I was based at Lossie (could it be a Scotland thing?? LOL). But had no trouble since.

360ste

iTrader: (1)

I know there are different version of the coil packs, something to do with charging time.
http://www.surefireonline.co.uk/category-s/1864.html


Not sure if this could have an effect.

Brettmck10

Haha aye maybe the salt in the air up here lol

Brettmck10

360ste did you work at GEF ?