Ok guys, my tuner and I have a little discrepany. I think that 4 injectors fire at a time...left bank, right bank. He says all 8 hit at the same time.

Reason why we are at this point is b/c i have a bad FP fluctuation in sync w/ engine speed. The guage bounces around from 30-90 or so psi telling me that:

1) bad injectors
2) some are "out of timing" like all 8 opening (and therefore closing) at the same time


the guage is good BTW. Brand new Walboro pump, new Accel 24# inectors and an older accel regulator....im lost man

*edit*: i called TPIS and was ready to order a regulator..the guy didnt want to sell me one b/c he really belives its the injectors and not a bad regulator...i thought that was pretty nice/professional of him to try and save me $80 or so.

 

They fire one bank at a time, left or right, not all 8.

 

Wrong, they all fire at the same time, both sides, all eight injectors. It is a batch fire system.

There are 2 signal wires going to the ECU yes, but they are internally tied to the single injector driver inside.

 

I have heard, and read (I think it was CHP) that it is one bank, then the other bank, four at a time. Now there are as many opinions on this thread as you already had. My gut tells me that they fire one bank at a time, otherwise they would be in constant spray mode (ala throttle body systems) and I don't think you'd be able to get the mileage out of these cars like you can if that were the case. I have read it in an article, where a guy wanted to change the firing order for some reason, and CHP (or Hot Rod) said it fires left then right. I don't know, all I care is that when I turn the key, it runs.

 

FACT -

Batch fire = all injectors fire at the same time

Bank to Bank = one side of motor fires first, then other side fires (separately)

Sequential = each injector fires individually


ALL Factory ECM'd thirdgen's that have TPI are batch fire.

 

OK, this is the final answer. All 3rd gen TPI cars were batch fired. This means both banks of injectors fire at the same time.

For proof I submit this factory diagram from a 1986 Camaro (MAF). It slearly shows there is only one injector driver inside the ECU (1227165). The '90-92 Speed Density ECU (1227730) is the same as well.

 

All 8 Fire


I was under the 4x4 impression at one time too.

 

I see there's still nobody who wants to hook up a test light or two.

 

 

votes on which one you think is the culprit???

Injectors or regulator????

 

hook up a fuel pressure regulator and check the pressure... I had an AFPR crap out on me out of nowhere...

 

No need when you have the factory wiring diagram.

 

my vote is for that the injectors being bad.

I've read many of the guru's on here say that ALL thirdgen TPI ECM's only have one injector driver. My understanding is that the time difference between when the injector sprays and the plug sparks is so small, that you really wouldn't notice much of a difference in mileage or performance.

 

i cant recall the exact reason (im sure madmax knows) but if you use a test light on the ECM you will cook it...

 

It draws to much amperage on what is already only about a .500ma circuit. You can use special injector testers though that don't draw on the circuit at all

 

onebinky...good point on the "too fast to notice", but my concern is the nitrous......

 

https://www.thirdgen.org/techbb2/sho...hreadid=230397

 

I've used a 6 volt test light many times and never "cooked" an ECU.