Injectors voltage problems/drop

[raddy]

Hi all

my mate stucked with problem with his vg30et, maybe someone can help us...he touched with live 12V feed of one injector to chassis for a moment,spark was produced, after this he hade following problem: engine can start normally, but it struggle to rev. It can rev up to about 5000rpm directly after start, at this rpm it become struggle. As engine is warming up, it can be revved less and less and soon it cannot even idle... Reason of struggle is lack of fuel as we seen at WB. After more examination I found that as soon as engine touch some specific rpm (which is changing with engine temp. as described above), fuel cut happens, AFR goes directly to 20:1. O.K., next check was with nistune. I found relation between required injector open time (or duty cycle) and fuel cut. As soon as ECU require for more duty cycle (throttle blip on neutral), injectors stop work, fuel delivery is interrupted. As soon ECU require shorter inj. time, it become normal again. And for end of the day, we found why fuel is shut-there is huge voltage drop (below 10V) at injectors as soon as ECU need more opening time, what cause shut off injectors.... By my opinion, higher frequency of impulses mean higher average current and then is more easy to get partiall shortcut between 12V and earth...
First idea was that inj. harness was damaged, but complete harness exchange doesnt help. We also try to use ECU in another car, working perfect. Checked all earthing at ECU side, looks O.K. At this point we really stuck...Anyone can help us with idea what to do or check to find reason of injector voltage drop? Thanks for your ideas.

[bachig24u]

Do the injectors individually pass testing, are the resistance on them all the same?

Check the wiring Diagram to find what other sensors are connected to the same 12V feed that was grounded.

[Matt]

At first I would have said injector driver was damaged, but since it works fine in another vehicle then must have been some damage to the cable then? cant be the injector and not sure what else?!

[bachig24u]

I was thinkning the same about the ECU, then I reread the post.

I was thinking another sensor must be paritally stuffed causing it or an injector with a low resistance is pulling the too much current from the circuit at the higher TP's. Never seen it but what else could have been damaged by the short circuit current that feeds the injector? (a few coils shorted out inside one??)
If it is another sensor causing it then I would think that raising RPM2,3,4 etc should hide the fault when the faulty sensor goes off scale.

[raddy]

hi, thanks for inputs...injectors resitance was tested and it correct at all injectors, wealso tryed another set of injectors, problem still appear. I think that idea with sensor is wort of try, we will disconnect them one each other to check if voltage drop comes...thanks again...