Hi everyone,

Ok Im having problems getting my car to start. It cranks but wont start.
I just bought and installed a 1991 engine harness because when I bought my whole jdm swap (1990 13bt) it came with a cut harness. I tried fixing it and got tired so I bought a complete one.
So now I dont know what to do everything is connected. My brother told me I had to splice some wires with the ecu harness, but I dont know which ones. I dont think the ecu is getting power, my fuel pump is on constant with KOEO and cranking.
I searched the forums since there is a ton of info on this kind of swap but never saw any real answers of what needed to be splice inorder to get the s5 harness to work with the s4 body harness.
Please help me out guys! I really want to get this running soon

Here is what I have:
1986 s4 n/a 5 speed
1990 s5 turbo II 5 speed swap
1991 s5 ENGINE harness

 

Did you look at this? https://www.rx7club.com/2nd-gen-archive-72/s4-na-turbo-swap-details-813825/


It helped me with the turbo swap on my S5

 

On an S5 ECU, pin 1A should have constant voltage.

 

is that power for the ecu?
Is there a specfic place I should get the 12v from? or just run a wire from the battery lol

 

yeah that was one of the first threads I read. good info and helped me get where im at now, but what the OP did was swap in a s4 13bt into a s4. Im doing s5 TII into a s4 so thats where I need help.

 

Actually, pin 1B powers the ECU with the key to on. Pin 1A is constant voltage for the purpose of storing information in the ECU which can be reset when battery voltage is cut such as disconnecting the battery. The car can start with pin 1A not connected but pin 1B definitely needs to be connected. Sorry for the confusion.


EDIT: If the injectors are firing or the coils are providing for spark then you know the ECU is powered up.

If the car is an S4 then the Main relay would provide pin 1B with voltage when key is to on via the B/W wire.

Pin 1A could receive constant voltage from any fuse powered by the BTN fuse which powers all of the battery buss fuses in the interior fuse box.

 

ok ok awesome, thank you satch, Il wire up what you said and see if anything happens.

 

If you checked for voltage at pin 1B w/key to on and there was voltage then you know it's already getting power. Same thing goes for verifying if pin 1B has voltage w/key to on if the injectors fire or if the coils have spark and checking for spark is easy as is checking the ECU pins.

 

alright I wired up 1a with constant (fused) voltage and 1b wired to the black and white wire on the main relay and it still wont start.
this is a dumb question but how do I check if the injectors are firing and if I have spark?

 

Remove one of the plugs from the leading coil and place the plug back in place except leave the smallest of gaps between the coil bore and the plug wire and attempt to start the car. Usually, this requires two people but if you did this in the dark you would see the spark if it was present. With key to on the B/Y wire at the leading coil must have voltage as one of the things necessary for the coil to spark.

 

test your coils for 12 volts with the key on,then insert an extra spark plug into the end of the plug wire and lay it across the left strut tower bolts for a ground, then turn over the car(starter) and have a friend tell you if the spark plug fires, you can also connect a ground wire to the base of the plug and ground that too, for your injectors open up your right side harness to the Engine and find the light green wires ( they are the ground trigger wires for the injectors)your power wires are black /yellow stripe.... the front primary inj is light green, the rear primary inj is light green with black stripe, the front secondary is light green with a white stripe the rear secondary is light green with a red stripe ..to test use a small pin and pierce tha green wires one at a time attach one end of a small light( similar to a side marker size) to that pin and hook the other end to the black with yellow line ( if it shows power) then simply turn over the engine and have watch the lights to see if they respond , if not you may not have power from the Ignition swith.......hope that helps , good luck