Rb25/30 Spark Problem :(

[Jem]

hey guys,

story goes like this, driving along and gave it a tad of a squirt in 2nd gear going up a hill, car misfired a little bit, i ignored it as i thought i must be running out of fuel as i was already low..

so i went and filled the old beast up, after taking about 10 seconds to turn over (usually instantly) i drove away, went to pull out on to the road and all of the sudden it wouldn't pull over 2500ish rpm, i thought that's very weird, as i was close to home i decided to nurse her home. max rpm became progressivly lower and lower till it got to the point where it was undriveable..

at first i suspected it was perhaps the fuel pump, so i had my eye on the knock light and monitering it like a hawk.. i have the alarm set at 30 counts per second and not once did it flash (power fc)..

from this point in the car would no longer start

after i got it home, i checked the fuel pump, all okay, checked fuel pressure, all okay.. i took the battery out and gave it a charge, and also pulled the seats out to do some other work, after i put it all back in i decided to try and turn her over for shits and giggles, and low and behold it started fine, i let it idle for about 5 minutes, then shut it off. about 20 minutes later i fired her over again, all good, gave it a rev in neutral to see if i could replicate any of the previouse symptoms but it reved fine. i tried starting the engine about an hour later and no go, would just turn over, so at this point i decided to check for spark (done with a timing light over the usual #1 plug wire at ignitor pack, it's a series 1) and no spark..

checked the 12V plug that connects to the coil side of the ignitor pack loom and it had 12V going too it, however when i performed a continuity test on the negative i could not get anything.. figuring that this must be the problem i then put in a temporary wire between that wire and the chassis to see if i could get her to turn over.. it obviously had current going through it as it sparked like all buggery when i connected it to the chassis, enough to make me double check to see i'd accidentally connected it to the 12V wire, which i hadn't.. i tried starting it but still no go..

i'm starting to think that perhaps the time without power gave whatever it was time to settle and come back good again, i can't see anything around the boot and rear seat area having any effect over the spark, so i think the seats in/out was just a coincidence, i'm thinking perhaps i have blown a ignitor pack, however i've got no pin diagrams and don't even know what the hell it does to be able to test it, unless of course it was just a loose earth somewhere, although everything else in the car works fine..

anyway, i would very much appreciate anybody's oppinion on the situation

many thanks in advance,

marcus

[Adriano]

Can you borrow an igniter off someone, and next time it happens, check the sensor/sw check screen to see if anything there is amiss, could be CAS

[Jem]

i pulled the cas off and flicked it by hand, could hear injectors opening and closing, but still no spark, so i don't believe it's the cas, all sensors read fine - i'm almost sure it has to be something in the wiring or actual igniter pack itself.. the fact it started perfectly twice randomly i think is telling me that it has to be a dodgy earth connection / relay somewhere.. access to the 33 gtst series 1 wiring diagram would help alot but so far i've been unable to find anything in my searches

[Adriano]

Check the ecu is earthed, adn there will be an earth wire for the igniter, sounds like igniter to me, except they usually only lose one or two cylinders, not all of them. Have you checked for power at the coils(not the igniter)

[Jem]

yeah, i've found a circuit diagram at http://i29.photobucket.com/albums/c258/dor.../r33english.jpg

looks like the way the ignition system works, the coils have a constant 12V into them, and the ignitor pack is a set of 6 transistors, which when supplied with with a pulse from the ecu connect the 12V from the coil packs to earth..

the 12V plug that supplies the coils has both a positive and a negative, the positive has 12V too it, but the negative in my case comes up with infinite resistance every time i measure it between that wire and the chassis, so i'm guessing this is my problem.. now my only issue is actually locating where abouts this is earthed to the chassis, or where abouts the break in the wire actually is :S

[Cubes]

2500rpm you say.....

Check the AFM.

[rob82]

yeah, i've found a circuit diagram at http://i29.photobucket.com/albums/c258/dor.../r33english.jpg

looks like the way the ignition system works, the coils have a constant 12V into them, and the ignitor pack is a set of 6 transistors, which when supplied with with a pulse from the ecu connect the 12V from the coil packs to earth..

the 12V plug that supplies the coils has both a positive and a negative, the positive has 12V too it, but the negative in my case comes up with infinite resistance every time i measure it between that wire and the chassis, so i'm guessing this is my problem.. now my only issue is actually locating where abouts this is earthed to the chassis, or where abouts the break in the wire actually is :S

If your on the signal wire then you will have infinite resistance as the trasistor will be supplied no signal from the ecu therefore the ground it uses to power the coil will be open circuit. There is however another ground on the coil that leads back to just under the ignitior back that should be bolted to the head - I'm not sure what the purpose of this ground is maybe to stop back EMF the car should however run without this ground - from memory.

[Jem]

yeah that is the ground for the high voltage side of the coil, she's fine.. the ground i'm talking about that measured infinite resistance is the one that runs with the main 12v power source for the coilpacks, it has a capaciter wired into it, hence the resistance readings.. this capaciter i guess serves to block out the DC coming from the main supply wire (all coils run in parallel from this wire that runs straight from the 12V source to earth) and only allowes through AC from the ignitor pack (AC in this case is pulsed DC).. anyway, i don't actually recall seeing this capaciter with my own eyes before so if anybody has any idea's where about's the f**ker actually is, please feel free to let me know

[kiwi32]

That wire may be the timing loop which comes off of the switched wire on the coil on #1 cylinder.

[Jem]

well as a follow up, here's what went wrong

the problem started to come to light when out of desparation i decided to pull off the CAS (even though i'd already pulled it out and tried testing it, and the car wasn't getting spark) i flicked it around a few times again to make sure i could here the injectors clicking away as they do - check, but then after giving it a bit of a wiggle and plugging it in again, i heard a bit of a defened boom, i was like wtf was that, thinking a bomb or something had gone off in my street.. then realised the car had been dumping excess fuel into the exhaust system and the coil packs must have been firing to set it off..

anyway so i through the old timing light back on and gave the cas another spin and a bit of a wiggle, and i got a flash

so i pulled the cas apart to find bits of metal floating around inside it.. not good, cleaned all of that out, and gave her a good spray with contact cleaner, also cleaning the plug and connecter, as they were dirty..

let it dry and put it all back together, cranked over the engine and BAM - worked first time

thanks for your help anyway guys, much appreciated

cheers,

marcus

[Cubes]

So where did the metal bits come from? :S

lol.

[Adriano]

Let me guess, the CAS has at some point been running without the cam pulley cover? Common cause for CAS failure.

[RB30-POWER]

Let me guess, the CAS has at some point been running without the cam pulley cover? Common cause for CAS failure.

But its worth it, because it makes your engine look hectik tuff br0!

[Bl4cK32]

till a rock flicks up under the timing belt. Then its uber tough looking on a tow truck