Looking at my factory manual I noticed that all 8 TPI injectors are fired from a single ECM ground. On the MPI 3.1, the fuel injectors are fired from 2 separate ECM grounds. Why would GM do that to the higher performing model and give the base engine the better route as far as injecting the fuel?

 

Since all 8 fire at the same time, I don't understand the concern?

 

It may sound crazy, but the wiring and injector grounds for the two are identical. Even though the 3.1 MPFI drawing shows what appears to be two injector drivers, there is only one in the ECM.

The drawing for the TPI setup is more accurate.

Note that the '90 - '92 TPI engines and 3.1l MPFI engines used the same ECM. But with different code bases in each.

RBob.

 

Ah, well that was simple! Just something that had had stuck out to me when I was looking through diagrams. Makes more sense that way.