TBI Injector polarity

[AlexanderHL]

Hi

Searched forums and internet for answers regarding this, but im still unsure.

Does the TBI injectors care about polarity?
The TBI housing have different grooves so that the injectors can only be assembled one way
Each in 180 degrees rotation from the other. So positive should always be on the outside, and common ground in the center?

However the official drawings doesn't indicate this when describing the coils in the injectors, it also doesn't indicate if injector 1 is on cylinder bank 1? I assume this is the case? However the wires comes from the backside, not the front as in drawing..?

Attached photo from 89 g20 wiring manual.

[PlayingWithTBI]

Hi

Searched forums and internet for answers regarding this, but im still unsure.

Does the TBI injectors care about polarity?
The TBI housing have different grooves so that the injectors can only be assembled one way
Each in 180 degrees rotation from the other. So positive should always be on the outside, and common ground in the center?

However the official drawings doesn't indicate this when describing the coils in the injectors, it also doesn't indicate if injector 1 is on cylinder bank 1? I assume this is the case? However the wires comes from the backside, not the front as in drawing..?

Attached photo from 89 g20 wiring manual.

Take a look again at your drawing. Yours shows Red/Red, is that right? Here's a diagram for my 88. Red and White are positive while Blue and Green are negative (grounded by the ECM. IDK if polarity matters, why not wire them the way they were originally?

The Intake manifold is designed so the injector on each side feeds the 2 center cylinders on that side and the 2 outside cylinders on the other side. These are fired synchronously, meaning they take turns, and if you look at the firing order, each one will fire for their assigned cylinder.

1988 Injector Control Circuit.PNG

[AlexanderHL]

Hi

Yes, my 89 has red/blue and red/green wiring on the wiring harness just as on the drawing.
I got quite a lenghty reply from a guy at the garage today about polarity in solenoids. If the solenoid has a iron core, polarity doesnt matter as the core always wants to return to "zero" in the coil. Its different if the core is magnetized. I think he knows his stuff, phd scientist guy buildning cars and stuff :)

regarding that they fire synchronously, how does the ECM know which bank is firing as the tbi lacks crankshaft position sensor?

BR
/Alex :)

[PlayingWithTBI]

Hi

regarding that they fire synchronously, how does the ECM know which bank is firing as the tbi lacks crankshaft position sensor?

BR
/Alex :)

Probably doesn't since it's a wet manifold system. I guess it's just a balancing act between injectors. I just find it interesting that timing would coincide between manifold design and injectors firing.

Does your engine actually have both red wires or, is it a misprint? Not that it matters - just curiosity.

[AlexanderHL]

Probably doesn't since it's a wet manifold system. I guess it's just a balancing act between injectors. I just find it interesting that timing would coincide between manifold design and injectors firing.

Does your engine actually have both red wires or, is it a misprint? Not that it matters - just curiosity.

:)
Couldnt find photo, but yes red/blue and red/green wire on car also :)

[steveo]

many gm dual injector tbi systems have two modes, one where both injectors fire in a pattern left and right, and one where both fire together. there is usually an rpm threshold for this so at higher rpm they fire at the same time.