how is or the best way to test for injector pulse





86 s4 n/a i have fuel press, spark, no injector pulse! https://www.nopistons.com/forums/pub...1047683358.gif





please help me

ALSO ALL EMISSIONS ARE REMOVED

id plug a spark CAS in, and spin it and listen for clicks, or you could hook a test light up

i tried the light and got nothing! any other advise?



this was w/ the cas installed and probing the ecu, cranking w/ starter

this might backtrack a bit, but i dunno what your car is doing...



so the coils and the injectors both get power from the same blk/wt wire, it comes out of the main relay and then branches off.



the when you power the ecu up, and give it an rpm signal, it will output spark and fuel.



for it to ONLY be doing spark it means a few things, in no particular order



1. bad injector? (i could see one, but 2?) it should have continuity, low imp is like 1-5ohms high is like 10-15, if you give it 12v and ground it should click



2. bad wire(s) this one is pretty easy, with the key on engine off, there should be 12v at each injector wire at the ecu. if not, there is a bad connection/wire somewhere. next step would be to check each section, ie ecu to resistor, resistor to injector, injector to connector under the dash...



3. bad resistor pack? again very simple to check



4. maybe the injector driver in the ecu took a dive?

what connector under the dash are you talking about j9 the ecu connector? this is great info thanks alot

it turned out to be a bad injector, slid in a cleaner pair of pri injector and she fired up after the third cranking! first time for me and the rotary, i was so happy my build started!!! https://www.nopistons.com/forums/pub...>/beerchug.gif https://www.nopistons.com/forums/pub...1047683329.gif https://www.nopistons.com/forums/pub...1047683329.gif

yeah thats a good feeling isnt it! congrats