quick question, what signals the injector to pulse. im getting strong spark from the coils, i hear the fuel pump running while cranking. only thing is no injector pulse. maf is connected, i cant figure out what else to check. thanks in advance

 

Which injectors are you trying to measure for pulse?

 

primaries isnt firing

 

Are you testing them at the ECU or somewhere else? The secondaries are located on top of the UIM. Are these the injectors you are testing. These are not used to start or idle the car.

 

i probed it at the ecu going off the fsm, no power. the car runs perfect off of starter fluid. theres fuel at the rail. i hear the pump running. the injectors are in known working condition. just no pulsing

 

Which ECU pins did you test? Were they 3C (Light Green/Black wire) and 3E (Light Green wire)? And how did you test them?

 

i just realized i was doing it wrong, i was checking those wires for positive using a grounded test light. i should of been looking for negative. ill check in the morning, but i feel my problem is still on the power side. is the black yellow wire suppose to have constant positive when igntion is on?

 

Which B/Y wire? If you are referring to the wire that powers the injectors then the answer is yes.

 

yup thats the one, i will check it out tommorow and see what happens

 

I used a probe and checked at the injector and with the car cranking, i found pulsing negative on one side and open circuit on the other. my question now is where is this b/y wire leading to the injectors. i cant seem to find it anywhere

 

Each injector has two wires. One is the B/Y wire. You won't be able to test it unless you pull off the UIM as it relates to the primary injectors or test the wire at the secondary injectors. Conversely, you can check the B/Y wire at one of two other places. At FEM-02 or at the Main Relay.

Also, if the trigger wires at the ECU had 12 volts w/key to on then that means the B/Y wire is receiving voltage at the injectors.

And if you have the resistor box for low impedance injectors you won't have B/Y wires at the injector as they will be Brown.

Lastly, if you used an LED light you could tell whether the primary injectors were being pulsed or not. One wire of the light would be placed to pin 3I (B/W wire) and the other wire to the trigger wire and w/key to start the light should flash.

 

i ran direct power to the 2 b/y wires off of the fem-02 and it ran for a couple seconds before dying out. so i guess im on the right track. thanks for your help.

 

Isn't there a way to check primaries? I think with ignition on you spin the CAS and listen for clicking using a probe going down touching the injectors. Or something like that.

Or at the ECU, with ign. on, ECU plugged in, grounding the injector ground signal wires by back-probing, using a jumper wire.

 

FWIW, I once had a resistor box that had an open in one of the primary injector circuits. The resistor is mounted below the air box and has a five-pin oval plug. Can't miss it. You should have a similar resistance between one common wire and the four branching to the injectors.

 

You could do those things.

 

i used a pin stuck inside the injector pigtail and had a friend crank the car while i checked.