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why guess.
why guess, you do know the car has a schematic.?
do you wont one for free so you can stop speculating .
most of what you are saying are wrong, not all.
the key switch my not be clear to you with a schematic.
it can have more than one position.
1: off ( all , , ignition, Coils, ECU, EFI, sensors, all) cept ECU memory. and HL.
2: on, this powers up all the parts. (not on, in #1 above)
3: START, cranks motor and tells ECU you are doing that.
4: some cars have accessory position that powers, just that.
there is distribution drawing.
this shows clearly what is hot all the time and what is not.
if you need this for your car just let me know. free.
Never on purpose , put a momentary (open) switch into your car
that powers on all the electronics , over and over .
this surges the electronics and is very bad for it.
There are exceptions, but in general do not do this unless you can prove it is ok to do so.
ever price an ECU/PCM?
Igitions are simple but in the global view they are complex that is because they are all different. many many kinds there are.
Ford,Chev. Toy,. Nissan, Suz. etc. and generations.
the best way to cut spark and fuel is to cut the Cam sender.
this kills the hall sensor output which is harmless.
on a new car it will set the DTC.
94 metro, the ECU , is very old , and are $200 to $400 exchange.
you kill power to the Distrubutor
and the main relay , fuel pump and a whole chain of stuff.
on a Metro, (inside cab , ok , i get you)
kill the power to the fuel pump, but the pressure may take 3 seconds to drop) and delay.
I am thinking ( know ECU real well , i repair them)
the ECU will go DTC for any cut to any sensor, but Injector (maybe)
cant cut TPS, or any.
yours has DIzzy based Cmp sender (a Cam sender hidden).
it too is monitored by ECU for shorts and opens.
I really would never cut power to the main feed.
not like this. (heavy usage) .
when you restart the ECU must go from Bump start to full closed loop cruise.
id bet it wastes fuel doing that.
this can be proven with a injector log device. (kits here , mpg gauge)
does this help.
study Latch up of semiconductors (google) and how surging is bad.
fyi.
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