*One more mkiii that won't crank =(
 

Hey guys, I've been trolling around here for a few years now since I first got my Mkiii. I couldn't believe it when I found it, and loved it for about a year until it quit turning over... Been sitting up over a year now and it's killing me. So, I've been reading all these other posts with the same problem and I just can't find an answer that makes sense - neither have I paid anyone to come try their magic at it.

This is what I HAVE tried -

Replaced starter
Replaced alternator
Replaced battery
Swapped out Starter Relay
Tried starting in neutral
Tried resetting security by hooking up battery while key is on, locking and unlocking both doors and trunk with key.

Now, I don't believe its a starter or starter cable problem because.... the ECT box is what clicks, not the solenoid. I pulled the cover off of the ECT today and just found a pcb with plenty of resistors/transistors but no relays or anything that looked like it could be clicking... Does anyone know if there may be another relay or fuse Behind the ECT in that passenger kick panel? Anyway, before I keep going on for days i'm going to stop and ask for ANY SUGGESTIONS, THANKS!

1990 Mk3 Supra
completely stock
1985 Celica GT
stock minus .20 over-sized pistons

hey man i could help you on this just hit me up with a private message i got some things you can try

Why would you do that? The whole point of a forum is so that other people can benefit from everyone's experience (sharing knowledge, helping people, etc)

The ECT box shouldn't affect the engine from cranking, as it is not part of the starting system wiring (per the TEWD). I assume this is an automatic, have you verified that your neutral start switch is operating correctly? Can you start it in neutral? Here is the wiring diagram for the starting system.

Thanks for the responses guys, but yes I have tried to start in neutral, and yes it is an automatic...

I did try swapping out another relay that was right next to the starting circuit one since they were the same kind... that didnt help either. Guess I should update my list on my original post ;)

I also had a guy I know at the local toyota dealership print that wiring diagram out for me and still didn't help...

I'm going to get a mechanic I know to come help me look it over more in depth... I'm just not comfortable with messing with wiring and things I cant just put right back. And it still just bugs me that when i turn the key that ECT box clicked... I mean, if it was the starter clicking I know how to fix that, but yeah.

Thanks

Looks like you've covered everything but .....the ignition switch?
Wiring can seem complicated but finding where the voltage stops is not. A $10 test light/probe and a 30 minute google or youtube session on how to use it can help you solve most of your electrical problems. These cars actually have pretty basic electrical systems, the wiring seems a bit excessive though.

Yeah, that's a possibility I'm going to try and rule out after I can check the neutral start switch. Although, it would seem power is traveling past the ignition switch since it's clicking over near the ect/ecu somewhere...

You would be better off investing in a good repair Manuel. One with a diagnostic section. If car will not start check a then b then c. It may be a very simple thingy. You should not start off replacing expensive parts hoping it is the failure. Think you can take things like starters down to some automotive shops to be checked. Guys think with your brains, save your money for tickets and insurance. :bouncy:

I agree, throwing parts at it isn't an efficient way to go about anything. First you figure out what is wrong before replacing anything at all. Its called diagnostics. If it had been done, you would likely only have made one repair.
Something is not completing a circuit here. A simple test probe light can pretty much diagnose this, buy one or borrow one. Any schematic, diagram or manual is available on the internet for free somewhere, you just have to look hard enough. Try to use the actual tsrm info over hayes or chiltons. They are helpful but seem quite generic in their info and diagnostic steps.
With the correct starting system schematic, a test light and a simple understanding of how to use both, you should find your problem quickly. Good luck.

I would love to be able to read the diagnostics on my Supra... Where can I get a scanner for the mk3? Most of the mechanic shops around here all turn me down when I tell them it's a 90 model... They only go back to 2000 or 1995

Btw, normally I would not just throw new parts at my car. I've been working on my celica since I got it over 15 years ago and never took it to a shop... Me and my dad rebuilt the engine. But when it comes to the electronics side I just don't like to mess with it. But with this problem, its been going on over a year and I have gotten desperate.

Thanks again for all the input guys.

That's not exactly what I meant by diagnostics but they do make a scanner for the 7mgte diagnostics= a multi-meter can tell you whatever the computer has to say. Learning how to use one will save time, money and improve the enjoyment factor of owning a mostly electronic controlled 20+ year old sports car. The correct diagram is posted in the 3rd post of your thread.
If you can rebuild an engine, you got this. An electrical circuit is hardly different then an oil passage circuit or a coolant circuit. If something causes resistance (dirt/corrosion/defective part), the flow will decrease until the fluid is no longer able to flow where it needs to go and eventually something will suffer. If there was a huge hole (broken hose,stuck t-stat=broken wire, defective electronic part) then the fluid would not make it where it needs to go at all because it will flow out of the new hole instead or may not flow at all because it's path has been disrupted and now something will quickly suffer. For an electrical circuit to exist electrons must make the loop exactly as the oil or coolant. Think of the battery and charging system as the oil pan and pump, the oil starts and eventually returns to the pan, electrons start and return to the battery. The alternator keeps the pressure up. Measuring electricity is like measuring the level, pressure and condition of your oil. I really hope that kinda helps.