Wiring 3.2 Help - Injectors all firing at the same time

[jamiesenna]

Hello,
Looking for a little help. My father and I have been building a mid engine 3.3 twin turbo 911, running 3.2 injection and DME. We have a chip burned to run the boost and a fuel pressure regulator modified for boost.The car has started with lots of forum help, but we are stuck. The car fires up runs ok, as long as you hold the throttle a little but all injectors are firing simultaneously and flooding the car to the point that gas pour out of the exhaust, WOW. Did we hook up a wrong wire? We have no factory harness running in the car, just the motor harness, cut at the end revealing colored wires. Can anyone point us in the right direction? Maybe a wiring diagram, pointing out what wires to connect?? Thanks in advance to all look!

[theiceman]

Silly me i thought all were sppose to fire at the same time .. oh well. i guess im about to learn something too.

[dtxscott]

I'm not familiar with your setup but, electrically speaking, this sounds like you have a bad ground for the injector harness. You may want to check the cleanliness and security of the injector grounds.

[Tippy]

Yes, all 6 fire at the same time. It's called batch fire.

Wondering if you have a short keeping the injectors open during cranking?

The Bentley manual does have the full injector wiring schematic.

[mytoy]

jamiesenna;

I may be wrong but I believe the 3.2DME is a batch fire system which means that all injectors fire at the same time.

The question is do you have stock injectors or did you change them out for something different?

If you changed them out for larger injectors did you have the chip programmed for the different injectors?

Are the injectors that you changed out ,(if you did), low impedance or high impedance? If high impedance did you have the chip reprogrammed for them as the stock units are low impedance units.

A little more info is required to asses your problems.

[turbobrat930]

Also, just a thought... my aftermarket ECU (LinkG4) gives and takes away ground to activate different things. My fuel injectors have constant, key-on power, and when they fire (Sequential, not batch fire), the ECU gives them, and then takes away ground to fire each individual fuel injector. Is the stock DME also using ground? Or is it using positive?

Some other probable causes.... What is your fuel pressure at? is your fuel pressure regulator working?

[Dick Shift]

Did you say, "building a mid engine 3.3 twin turbo 911" Key word "Mid" Pictures please!

[E Sully]

The stock Motronic injectors are wired in parallel to fire at the same time using ground, with constant power supplied to the injector. If you have the original engine harness, you can't get a sequential fire instead of batch firing. If the chip is trying to fire sequentialy, it would activate all the injectors instead and cause your excess fuel issue. You would need different harness wiring to the injectors, or get a chip designed for batch firing.

[wjdunham]

Do the injector banks (left and right) both fire together as well? The reason I ask is that I am assembling an engine that I purchased in pieces, and it's not clear on the engine side harness which one of the branches is for the left side and which is for the right. The diagram above shows the GRY/WHT side going to the left bank (cylinders 1, 2, 3) and the GRY/BRN to the right bank (4, 5, 6).

Thanks in advance as always.

Bill

[FrankM_]

Yes, both banks fire at the same time, pin 14 and 15 of the dme are internally connected.


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[wjdunham]

Awesome, thanks for the info. I have that whole harness figured out now, thanks to all of the wonderful info on this board!

Bill