OK, I know it must be the computer because thats where the injector wires probably come from. But then how does the computer know when to pulse them.....in other words, how does the computer know when the spark plugs are firing? I have an '86 Iroc TPI and as far as I know there is no crank position sensor in our cars. Does one of those wires coming from the distributor relay back to the computer and tell it when to pulse the injectors?

 

theres a pickup in there... so yea... thats also how it gets the RPMs...


since its not sequential injection it fires the injectors as a group....

so i think it fires a bank every other rotation....

 

I was under the impression that each injector would fire at a different time (I thought TPI was sequential), thus the advantage over TBI. I've never read that or heard that, but that is just what I assumed, so I could be waaay off. Problem is I replaced my 305 with a 350 and LT1 injectors. Car won't start, I do have the plugs firing and I've got TDC for number 1 pegged (compression stroke). What is the recommended timing for the TPI cars? Before I spend another night on it, I was wanting to know how the computer knows when to fire the injectors, and it seems to be the distributor (I had to make sure I didn't miss some other sort of sensor and the computer wasn't getting the input to fire the injectors).

 

the ECM gets a reference pulse from the ignition module. then it fires teh injectors. there are 2 drivers. one for each side of the motor. they fire in batch. the wire is in the 4 prong harness. can't remember which color offhand. here's a wiring diagram.

http://fl-thirdgen.org/wiringdiagram.html

 

Umm no. All F-body TPI ECM's have one injector driver. The injector banks are wired in parallel internally.

 

wow and to think by looking at the wiring diagram there are two wires coming out of the ECM. and of course one can die out.