TBI wiring

[mouse]

I have almost finished prepping my TBI harness for install but could not find the pin-out digram for the 7747 ECM. Anyone help me with the following wires?:

Purple wire to ECM pin C9. Goes through firewall bulkhead conector (at fuse block). I think this is just a starter signal to ECM. Does it connect to starter circuit?

Tan/blk wire to ECM pin D5. It goes back to the fuse block connector at firewall. I think this is the "set timing" wire, but I don't know why it goes back to the firewall???

Finally, the wires to the oil pressure sending unit:
orange - I think this is ign "on" 12 v power
tan/wht - I think this goes to pin B2 on ECM and is just a fuel pump signal to ECM. Again, why does it go to the firewall fuse block connector?
Tan wire (to fuel pump??)

Thanks for the help!!

 

[btolenti]

-The purple wire to C9 goes to the small terminal on the starter solenoid. I believe it tells the ECM when the motor is cranking. -The Tan/blk wire to D5 is the EST bypass wire. It should go to the distributor. -orange (should be at B1) is +12V battery fused (on all the time). The pink/black wire at A6 should be +12V ignition fused (on during cranking and run) -Tan/Wht (should be at B2) is the electric fuel pump feed. Basically this should supply the 12V power (fused) through the fuel pump relay to the fuel pump. The actual wire to the fuel pump should be an orange wire from the fuel pump relay. -Tan wire (to D6) is the Oxygen sensor ground. Basically, it is just connected straight to ground. I have a whole bunch of TBI diagrams. If you want them, PM me your e-mail address and I can send them to you. I just went through the TBI process (successfully). Glad to get rid of my CCC system.

 

[Suprzuk]

Here is a bunch of documantation that I collected while I was shooting a fuel pump trouble. http://n2zpy.catskill.net/GMC/87GMCdiagrams/

Kevin

 

[mouse]

Thanks for the replies. I am still debating on using the '89 electrical oil pressure gage instead of the '77 mechanical one. If I do, then I don't need to "T" the oil pressure tap. One snag is that my engine reads 80+ psi cold and 60+ warm, which is the max on the gage.