After doing some more reading I have found that the ecu should send a ground signal to pin 1 or the signal wire. I set up a 12v light bulb and found that the light bulb never flashes when the engine is cranked. I does dim when cranked but must be from load on the system. I ran some additional ground wires from the intake to the block and block to frame with no change. Anyone know how to further diagnose this issue?

 

-Are the yellows the same resistance as the previous injectors? (hopefully)
-The 550cc injectors will automatically pump substantially more fuel for the same ecu pulse, hopefully they aren't "flooding" and preventing spark
-I would check to make sure the cam sensor isn't unplugged or damaged and make sure the wiring around the injectors isn't pinched or damaged. Makes no sense the ecu pulse would stop unless something is damaged or unplugged.

 

Key on engine off you should only have 12 volts on one terminal at each injector connector. The ecu grounds the other to fire the injector. So if you have 12v at both, you either have a short to voltage in the injector driver circuit or a bad ecu.

 

The way to find this out would be to unplug all injectors and connect a small 12v light bulb to each pin of the injector connectors. You do this with the key on and not running. One will light up and the other won't, because the load of the bulb will drop any residual voltage on the pin that sends the negative pulse. If you are checking the power with the injectors plugged in, the 12v+ will read on both pins because the coil of the injector is sending voltage to the other pin as well. This is because digital multimeters have a high impedance and will not drop the load, and can see residual or low current voltage easily.

If you are checking for pulse while cranking, also disconnect all injectors (just to be consistent) and connect the bulb to both pins of one injector connector.

If you try checking pulse between ground and an injector pin, it won't work. You have to use 12v+ for one side (that is supplied on one side of all injector connectors) and the other side has to be the injector - pulse pin.

 

Just got home from a long vacation and swapped in my factory rails and injectors and the car fired right up. Not sure what's wrong with the injectors but the car started just fine with both my z4 and rob tune ecus. Anyone know how to diagnose the injectors?? Thanks for the help so far guys.

 

Are the injectors used? Did you get them cleaned and flow benched? Sending them to get cleaned will reveal any issues as they need to be cycled to be cleaned.

 

I purchased them used with a flow test completed the week prior to purchase. I have the paperwork for it. They were flow tested somewhere around early 2013 so they have sat for a bit but look great. I doubt that they could all be bad. I used a multimeter to check the resistance and all 8 injectors were within the same ohm range.

 

I don't know mine sat for over a year before I installed them. Also my 550s ran on both the stock tune and robtune.