Wont turn over, giz some advice

[Vertigo]

Sup, my AW developed an electrical problem last night. Went to start it, nothing. Fiddled with the battery terminals, got it started, but when I turned the lights on, big rpm drop and the tach went mental, so turned it off. Wouldnt start again after that. Im getting dash lights when turned to ON, except for the check engine light which should come on (at least I think I remember that it does).

All accessories, wipers, headlight motors, all work fine. Just does nothing when I turn the key. Im suspecting the ECU has $&#$% out, but Id rather eliminate all possibilities first.

Also, if you suggest any fuses/relays to check, please note which one it is, all my diagram stickers have been lost to the sands of time ;D

[Vertigo]

Ok, while trying to diagnose, I tried the starter motor by jumping the relay connectors - turns over, but without the ecu its not getting fuel (we checked a fuel injector lead with a multimeter while turning over).

When we attempted to check spark with a multi-tool stuck up an HT lead, we got spark, stopped, then while waving the lead around managed to get the engine light to come on briefly, while at the same time heard the main relay click. There was no discernable pattern to our waving that made it do that

Im checking all the grounds now, but this sounds all very odd.

[Vertigo]

Grounds seem fine, have redone most of them now.

It seems that the main relay is receiving 12v constantly on the trigger side, even when the car is off. I think the main relay is dead now, also, but will test this properly soon.

I stuck a couple of headers into the correct terminals of the main relay and shorted them (to emulate the relay on), and all sorts of weird shit happens - fans come on and off, engine check dash light comes on and off, relays flicker madly. Looking at the wiring diagram, there must be a short on the H wire (see diagram) to the positive battery terminal. Perhaps the ignition switch is $&#$%? But it seems to work alright, in that lights go on that should go on (except the engine check light).

Pics:

[Lloyd]

Which pins are you jumping exactly???

[MrOizo]

I had a problem like this in my AW11 yearrrssss ago.

I forgot to put a earth from engine to chassis which burnt out some of the wiring in the rear boot. I guess the earth was doing all the work of the engine-to-chassis earth.

[Pelo]

How is your battery? Might not be putting out enough current to power the starter, fuel pump, ecu and injectors all together.

[Vertigo]

Lloyd, if you look at the diagram, Im jumping pins 5 and 4 on the engine main relay, with the ignition switch to the ON position. Thats what makes shit freak out, but it shouldnt.

Battery should be fine, replaced it last year. The battery terminals were a bit naff, but I cleaned those up.

Frustrating problem. Wouldnt mind someone coming to take a look, thats good with this shit.

[Vertigo]

Found the issue finally. Its an intermittent short in the loom for the starter motor.

[Vertigo]

Strangely the two wires for the starter are ok. Its possibly the engine bay temp sensor wiring, or the engine water temp sensor wiring, both in the same part of the loom. Jiggling these wires gives shorting sounds and relays firing, and occasionally the fans all come on and the engine check light also.

Then Ill leave them alone, and for no reason everything stops.

[Vertigo]

Im in serious need of help with this one. Id love if someone could take a look. Already gotten Hometune to come along and take a look, they did a bunch of diagnostic work early on but I called it off as it was getting expensive. I need this car running!

[blindnz]

If you know where the issue is (a short in the starter loom) can't you replace/re-wire the loom?

Am I missing something?

[Vertigo]

Replacing the loom at this point seems a very sensible option.

[allencr]

Strangely the two wires for the starter are ok. Its possibly the engine bay temp sensor wiring, or the engine water temp sensor wiring, both in the same part of the loom. Jiggling these wires gives shorting sounds and relays firing, and occasionally the fans all come on and the engine check light also.

Then Ill leave them alone, and for no reason everything stops.

Jiggling these wires gives shorting sounds and relays firing, and occasionally the fans all come on and the engine check light also.

That is an open circuit, not a short circuit, and usually caused by a bad crimp from a terminal to a wire or a bad terminal to terminal contact in a connector.

[Vertigo]

The reason why I think theres a short is because the battery runs flat when the car is off (no lights left on either).

(Probably should have mentioned that but theres so much that Im getting overwhelmed).

[Vertigo]

Follow up.... after 4 month off the road, 3 of them being dicked around by my mechanic who for mates rates did $&#$% all in that time, took it to Damian at A1 Turbos and he found and fixed the issue in 3 hours

Turns out it was some dodgy corroded connectors just behind the passenger seat! Runs bloody well now ffs... anyway, just in case someone has a similar issue..

[Bling]

Good to hear you got it sorted in the end. Also nice work on finishing off the thread, so many never have the answer posted at the end haha.

[MilfHunter]

Thanks for the updates
On the ST16x Celica's it's common for the starter to die due to corrosion in the loom which is remedied by fitting a relay to the starter wire.