AE86 Start signal

[Granto]

*puts on his retarded hat*

okay

my start signal forthe starter motor is earthed.

is that normal?

when you turn the key it goes to like 0.03 volts

I suffer big voltage drop (to 7v) during cranking.

is that normal?....

[ke70dave]

little unclear as to what exactly your talking about, on the starter motor there are 2 wires

1 - big fat positive straight from the battery
2 - a normal sized wire that comes from your ignition barell, which is your solenoid trigger wire

if that solenoid trigger is earthed it will just cause a dead short = bad, might explain your uber voltage drop.

if it was the trigger wire that was earthed, I would expect no cranking at all

exactly how is it earthed?

[Granto]

multimeter plugged into the solenoide switch wire (earth on multimeter)
red multimeter wire goes to battery +ve
multimeter reads 12V

This leads me to believe that the starter signal wire (not the big power thingo) is earthed(right?)

leaving the multimeter there, and turning the key to start, it drops to zero

the headphuckery thing about it is, the car will still crank.

So this is making me think it's earthing somewhere, so, when the car is cranking there's a massive short and it can't do what it's meant to and etc.

[ke70dave]

ahh ok

well basically if a wire isn't supplying positive, then it is grounded (it's just how it is)

so the fact that the wire is earthed when your not cranking is normal

and the zero reading you get is also normal (when you are cranking), because the trigger wire will be 12V positive, and the other end of multimeter is also connected to 12V positive (the battery), so the potential difference between the 2 points is zero volts (remember multimeter measures potential differences, not absolute voltage, essentially all measurements are potential differences anyway)

so from what you have said everything is connected up normal

if the car cranks normally and actaully starts then I cannot see any problems, voltage drop will occur cuase remember you are pulling like 30amps from the battery, somethings gota give!!

does this make sense?

[Granto]

nah it dosent start

I get no fuel/spark during cranking

but if you turn it to ignition on, and spin the dizzy by hand, you get fuel and spark..

so ah, hrm, yeah, wtf.

it's been like that for months.

[Granto]

okay that's weird.

1. turn car to start and check spark/fuel, sparks once twice or thrice then no more spark/fuel.
2. remove dizzy from engine, and spin by hand in ignition, have constant spark/fuel.
3. have starter motor disconnected but turn switch to START and spin dizzy by hand, we have fuel and spark still
4. reconnect starter, spin dizzy by hand, we have fuel spark still (while engine is cranking) thought he spark/fuel is a bit weaker than when not cranking.
5. this has left me totally confused.

maybe the problem has magically fixed itself, but I doubt that.

[ke70dave]

ohh ok thats kinda weird, I don't have much experience with much else

isn't there a cranking signal on a 4age computer? (I assume it's 4age) that coudl be somethign to do with it

anyone else got any ideas?

edit just read your reply, I'm so confused, dodgy connection?

[Granto]

but dodgy connection to what?

There was a cranking signal for the original AE86 ecu, which I've replaced with a stinger 4424 thingo.


so I was thinking maybe that wire cranking signal I disconnected was shorting and fuxing shit up.

but then, why would it still be able to spark/fuel while cranking the starter but spinning the dizzy by hand (it's sorta confusing)

[Hen is a total nutcase]

Could it just be that your battery is stuffed.

If I understand right, it'll spark and inject if you spin the dizzy by hand with the starter disabled. However if you crank it normally with the starter then you get no spark and fuel.

The only difference is the starter will be pulling power in the second case. If your battery voltage drops too low (below 9-10 V)then you can get strange issues.

Also the starter signal wire should be open (neither earthed nor powered) normally. With the key at STA then it should have 12V. It's pretty easy to check that.

Hen

[Granto]

it'll also spark if you're spinning the dizzy by hand while cranking the engine.

so the starter motor is going, turning the engine while the dizzy is sitting in your hand having the cam gears spun .. it'll spark ( I did that to check if it was the starter causing too low voltage to make the ecu shut off)

and the fact it still sparked like that, has made me verrrrrry confused.

[Hen is a total nutcase]

Maybe a stupid question, but could you have snapped a timing belt. Hence dizzy not turning while cranking?

[ke70dave]

thast a very good point hen

take off your dizzy cap, and crank it over with the dizzy in the engine, does the dizzy rotor spin?

[Granto]

Maybe a stupid question, but could you have snapped a timing belt. Hence dizzy not turning while cranking?

That is a great question that no one i've spoken to about it has actually asked me!

-runs outside to check-

timing belt has good tension.. tensioner seems right..

I've thought about it a bit, and I'm starting to think for some reason with the dizzy in the head it's switching the ecu off while cranking. i'll have a play with it this weekend, i'll try jumping the car off my other car to make sure it's not some weird voltage issue, er actually i'll buy a new battery anyway.

i just can't logically see what the difference betwen the dizzy being in the head and the dizzy not being in the head would be electronically, but hen you just pointed that out, the cam actually spinning the lil thingie bit.

my mechanic thinks it might be something screwy with the dizzy, and he's probably right!

ah well.

till the weekend eh

[Hen is a total nutcase]

Only other thing I can think of is when attached the dizzy body will be earthed through the head. When in your hand it wont be.

I may be able to come over and take a look over the weekend (depends how I'm feeling Sunday morning) if you'd like some help. Sounds like an interesting problem. PM me if you're interested.

Hen

[Granto]

well, i had a chat to my mech as i said, to cut a long story short, i tried tonight, plugging the dizzy into the head exactly as is, without bolting it in (bad idea i know hah) and ...


drumroll

i had spark and fuel! wtf?


using a different battery.

so... who knows, maybe i'll actually make it to the next track day, and eventually, drift meet.

DavisJD.. Your meww mewww supercharger is going down ;)

[Granto]

spoke too soon. tried it again. no good. just as before, noid light flashes on the injectors about 3 times then that's it. i think it might be the dizzy.

[DavisJD]

Looks like the meww meww supercharger aint going down just yet! :P

[Granto]

*removes your teflon coating*

[Granto]

http://youtube.com/watch?v=6H9-3BNowio

http://youtube.com/watch?v=WyMPPt2XFcs

just so you can see what im on about :P (even tho it's super dark)

[slide86]

it sounds like the battery is not doing a good job of cranking by that first video ie low voltage

[Granto]

okay well after fitting a new starter today, and cleaning up some wiring, something went beeezerk.

now i think the internal ignitors on the ecu have fried again. (I think for some reason, the keybarrelwas in ignition! doh)

so looks like i'll have to send the ecu off to be repaired again.

howeverr, before that happened, i had it cranking with the spark and fuel going for longer than before. (while it was being jump started) this lead me to thinking maybe it was the starter, and buying another 2nd hand starter, and it not being the right one, so messing around with that for hours, and getting it hooked up only for something bizzare to go wrong, and yeah.


I'll have a play with it tomorrow i guess, then just probably take it to my mechanic, and maybe get a microtech or something.