short in AM2 circuit

when i put the key to the on position the 30 amp am2 fuse blows, no other fuses will go out and the car will still crank, i have started looking over the wires to and from the cam position sensor, ignition coils, and the igniter. i havn't noticed anything from those wires and am starting to think i won't find it, does anyone know of anywhere i can get the new wiring harness cuz toyota has stopped making them. if not does anyone have a good way to find shorts? its a 7mgte btw, new cam sensor, new igniter, and a python 700 alarm system if that can cause any problems.
 

figgie

Supramania Contributor
Mar 30, 2005
5,224
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Twin Cities, Minnesot-ah
Well lets take a gander at the TEWD and see what is getting fed from the AM2 fuse..

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=36

Feeds the 7.5 IGN fuse and the 15A EFI Fuse. More than likely these two fuses are fine. Check them anyway. If they are not blown, focus on the injectors (they get fed off the IGN2 switch in the starting tumbler). That is the only system that gets feed without a fuse save for AM2. Disconnect the inline resistor pack

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=111

and see what happens. More than likely you wont pop the fuse. if you don't Then it is a matter of finding if one or more injectors are fried OR the injector resistor pack is shorted to ground.
 
3p141592654;1168404 said:
It also feeds the ignitor/coils so you might want to look around there too for trouble if the injectors check out.

ive decided to replace the harness once i move i cant have wires goin bad on me, i checked around the coils and ignitor and the cam sensor and under the dash and couldnt find anything. btw with all the injectors and that other thing unplugged the fuse still popped
 

Dr Chill

4 hungry Supras
Nov 27, 2007
329
0
0
47
Mississippi
Im having a similar issue , But my EFI fuse blows instantly , key on , or with the key off .
If I happen to resolv my issue I will post up the info .
 

suprarx7nut

YotaMD.com author
Nov 10, 2006
3,811
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www.supramania.com
How have you determined the wire harness is to blame for a blown fuse?

...especially when you're not even sure what exact part of the circuit is the problem?

I'd find the exact source of your problem before dropping ~500 bucks and spending at least a weekend pulling the motor and replacing the harness. I would feel like a damn fool if I replaced the harness, started it up and blew that same fuse again because I didn't fix the actual problem...
 

Dr Chill

4 hungry Supras
Nov 27, 2007
329
0
0
47
Mississippi
suprarx7nut;1209586 said:
How have you determined the wire harness is to blame for a blown fuse?

...especially when you're not even sure what exact part of the circuit is the problem?

I'd find the exact source of your problem before dropping ~500 bucks and spending at least a weekend pulling the motor and replacing the harness. I would feel like a damn fool if I replaced the harness, started it up and blew that same fuse again because I didn't fix the actual problem...


I feel ya on that , I would at least trace in down 1st ... Replace 1 or 2 wires & be done with it .
Replacing a whole harness is quite a task .
 
Dr Chill;1209591 said:
I feel ya on that , I would at least trace in down 1st ... Replace 1 or 2 wires & be done with it .
Replacing a whole harness is quite a task .

well i got lucky, turns out that when i put the engine back together after the rebuild i routed the harness wrong and the egr burned through some wires, had a shop fix it cuz of an injury but at least i didn't get too involved with it, thanks for all the help guys.